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@article{faucris.108483364,
abstract = {The multi-junction concept is the most relevant approach to overcome the Shockley-Queisser limit for single-junction photovoltaic cells. The record efficiencies of several types of solar technologies are held by series-connected tandem configurations. However, the stringent current-matching criterion presents primarily a material challenge and permanently requires developing and processing novel semiconductors with desired bandgaps and thicknesses. Here we report a generic concept to alleviate this limitation. By integrating series- and parallel-interconnections into a triple-junction configuration, we find significantly relaxed material selection and current-matching constraints. To illustrate the versatile applicability of the proposed triple-junction concept, organic and organic-inorganic hybrid triple-junction solar cells are constructed by printing methods. High fill factors up to 68% without resistive losses are achieved for both organic and hybrid triple-junction devices. Series/parallel triple-junction cells with organic, as well as perovskite-based subcells may become a key technology to further advance the efficiency roadmap of the existing photovoltaic technologies.},
author = {Guo, Fei and Li, Ning and Fecher, Frank W. and Gasparini, Nicola and Ramírez Quiroz, César Omar and Bronnbauer, Carina and Hou, Yi and Radmilovic, Vuk V. and Radmilovic, Velimir R. and Spiecker, Erdmann and Forberich, Karen and Brabec, Christoph},
doi = {10.1038/ncomms8730},
faupublication = {yes},
journal = {Nature Communications},
keywords = {GEOBASE Subject Index: fuel cell; photovoltaic system; solar power EMTREE medical terms: Article; electric current; electric potential; electrical equipment; multi junction photovoltaic cell},
peerreviewed = {Yes},
title = {{A} generic concept to overcome bandgap limitations for designing highly efficient multi-junction photovoltaic cells},
volume = {6},
year = {2015}
}
@article{faucris.119149844,
abstract = {Trap-assisted recombination is one of the main loss mechanisms in bulk-heterojunction (BHJ) solar cells. Results suggest that introducing a near infrared (NIR) polymer into the 2,3-bis(3-(octyloxy)phenyl)quinoxaline (PIDTTQ):[6,6]-phenyl C butyric acid methyl ester (PCBM) host system suppresses trap-assisted recombination in the binary blend, leading to a significant improvement of ≈60% in power conversion efficiency for ternary organic solar cells at low light intensity.},
author = {Gasparini, Nicola and Salvador, Michael Filipe and Fladischer, Stefanie and Katsouras, Athanasios and Avgeropoulos, Apostolos and Spiecker, Erdmann and Chochos, Christos L. and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.1002/aenm.201501527},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {IR sensitization; low light intensity; organic solar cells; recombination; ternary blends},
peerreviewed = {Yes},
title = {{An} {Alternative} {Strategy} to {Adjust} the {Recombination} {Mechanism} of {Organic} {Photovoltaics} by {Implementing} {Ternary} {Compounds}},
volume = {5},
year = {2015}
}
@article{faucris.123665124,
abstract = {An attractive method to broaden the absorption bandwidth of polymer/fullerene-based bulk heterojunction (BHJ) solar cells is to blend near infrared (near-IR) sensitizers into the host system. Axial substitution of silicon phthalocyanines (Pcs) opens a possibility to modify the chemical, thermodynamic, electronic, and optical properties. Different axial substitutions are already designed to modify the thermodynamic properties of Pcs, but the impact of extending the π-conjugation of the axial ligand on the opto-electronic properties, as a function of the length of the alkyl spacer, has not been investigated yet. For this purpose, a novel series of pyrene-substituted silicon phthalocyanines (SiPc-Pys) with varying lengths of alkyl chain tethers are synthesized. The UV-vis and external quantum efficiency (EQE) results exhibit an efficient near IR sensitization up to 800 nm, clearly establishing the impact of the pyrene substitution. This yields an increase of over 20% in the short circuit current density (J ) and over 50% in the power conversion efficiency (PCE) for the dye-sensitized ternary device. Charge generation, transport properties, and microstructure are studied using different advanced technologies. Remarkably, these results provide guidance for the diverse and judicious selection of dye sensitizers to overcome the absorption limitation and achieve high efficiency ternary solar cells.},
author = {Ke, Lili and Min, Jie and Adam, Matthias and Gasparini, Nicola and Hou, Yi and Perea, Jose Dario and Chen, Wei and Zhang, Hong and Fladischer, Stefanie and Sale, Anna Chiara and Spiecker, Erdmann and Tykwinski, Rik and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.1002/aenm.201502355},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {Absorption limitations; Charge transport; Near-IR sensitizers; Silicon phthalocyanine; Ternary solar cells},
peerreviewed = {Yes},
title = {{A} {Series} of {Pyrene}-{Substituted} {Silicon} {Phthalocyanines} as {Near}-{IR} {Sensitizers} in {Organic} {Ternary} {Solar} {Cells}},
year = {2016}
}
@article{faucris.123358004,
abstract = {Low-bandgap near-infrared polymers are usually synthesized using the common donor-acceptor (D-A) approach. However, recently polymer chemists are introducing more complex chemical concepts for better fine tuning of their optoelectronic properties. Usually these studies are limited to one or two polymer examples in each case study so far, though. In this study, the dependence of optoelectronic and macroscopic (device performance) properties in a series of six new D-A-D-A low bandgap semiconducting polymers is reported for the first time. Correlation between the chemical structure of single-component polymer films and their optoelectronic properties has been achieved in terms of absorption maxima, optical bandgap, ionization potential, and electron affinity. Preliminary organic photovoltaic results based on blends of the D-A-D-A polymers as the electron donor mixed with the fullerene derivative [6,6]-phenyl-C-butyric acid methyl ester demonstrate power conversion efficiencies close to 4% with short-circuit current densities (J ) of around 11 mA cm, high fill factors up to 0.70, and high open-circuit voltages (V s) of 0.70 V. All the devices are fabricated in an inverted architecture with the photoactive layer processed in air with doctor blade technique, showing the compatibility with roll-to-roll large-scale manufacturing processes.},
author = {Chochos, Christos L. and Drakopoulou, Sofia and Katsouras, Athanasios and Squeo, Benedetta M. and Sprau, Christian and Colsmann, Alexander and Gregoriou, Vasilis G. and Cando, Alex Palma and Allard, Sybille and Scherf, Ullrich and Gasparini, Nicola and Kazerouni, Negar and Ameri, Tayebeh and Brabec, Christoph and Avgeropoulos, Apostolos},
doi = {10.1002/marc.201600720},
faupublication = {yes},
journal = {Macromolecular Rapid Communications},
keywords = {Conjugated polymers; Donor-acceptor; Low bandgap; Near-infrared; Organic photovoltaics},
peerreviewed = {unknown},
title = {{Beyond} {Donor}-{Acceptor} ({D}-{A}) {Approach}: {Structure}-{Optoelectronic} {Properties}-{Organic} {Photovoltaic} {Performance} {Correlation} in {New} {D}-{A1}-{D}-{A2} {Low}-{Bandgap} {Conjugated} {Polymers}},
volume = {38},
year = {2017}
}
@article{faucris.112905144,
abstract = {Organic solar cells that are free of burn-in, the commonly observed rapid performance loss under light, are presented. The solar cells are based on poly(3-hexylthiophene) (P3HT) with varying molecular weights and a nonfullerene acceptor (rhodanine-benzothiadiazole-coupled indacenodithiophene, IDTBR) and are fabricated in air. P3HT:IDTBR solar cells light-soaked over the course of 2000 h lose about 5% of power conversion efficiency (PCE), in stark contrast to [6,6]-Phenyl C61 butyric acid methyl ester (PCBM)-based solar cells whose PCE shows a burn-in that extends over several hundreds of hours and levels off at a loss of ≈34%. Replacing PCBM with IDTBR prevents short-circuit current losses due to fullerene dimerization and inhibits disorder-induced open-circuit voltage losses, indicating a very robust device operation that is insensitive to defect states. Small losses in fill factor over time are proposed to originate from polymer or interface defects. Finally, the combination of enhanced efficiency and stability in P3HT:IDTBR increases the lifetime energy yield by more than a factor of 10 when compared with the same type of devices using a fullerene-based acceptor instead. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.},
author = {Gasparini, Nicola and Salvador, Michael Filipe and Strohm, Sebastian and Heumüller, Thomas and Levchuk, Ievgen and Wadsworth, Andrew and Bannock, James H. and de Mello, John C. and Egelhaaf, Hans Joachim and Baran, Derya and Mcculloch, Iain and Brabec, Christoph},
doi = {10.1002/aenm.201700770},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {Butyric acid; Defects; Degradation; Fullerenes; Open circuit voltage; Organic solar cells, Enhanced efficiency; Light soaking; Nonfullerene acceptor; Open circuit voltage loss; P3HT; Poly-3-hexylthiophene; Power conversion efficiencies; [6 ,6]-phenyl-C61-butyric acid methyl esters, Solar cells},
peerreviewed = {unknown},
title = {{Burn}-in {Free} {Nonfullerene}-{Based} {Organic} {Solar} {Cells}},
year = {2017}
}
@article{faucris.200517277,
abstract = {Fullerenes have formed an integral part of high performance organic solar cells over the last 20 years, however their inherent limitations in terms of synthetic flexibility, cost and stability have acted as a motivation to develop replacements; the so-called non-fullerene electron acceptors. A rapid evolution of such materials has taken place over the last few years, yielding a number of promising candidates that can exceed the device performance of fullerenes and provide opportunities to improve upon the stability and processability of organic solar cells. In this review we explore the structure-property relationships of a library of non-fullerene acceptors, highlighting the important chemical modifications that have led to progress in the field and provide an outlook for future innovations in electron acceptors for use in organic photovoltaics.},
author = {Wadsworth, Andrew and Moser, Maximilian and Marks, Adam and Little, Mark S. and Gasparini, Nicola and Brabec, Christoph and Baran, Derya and Mcculloch, Iain},
doi = {10.1039/c7cs00892a},
faupublication = {yes},
journal = {Chemical Society Reviews},
peerreviewed = {Yes},
title = {{Critical} review of the molecular design progress in non-fullerene electron acceptors towards commercially viable organic solar cells.},
url = {http://pubs.rsc.org/en/content/articlelanding/2018/cs/c7cs00892a#!divAbstract},
year = {2018}
}
@article{faucris.115944444,
abstract = {In recent years the concept of ternary blend bulk heterojunction (BHJ) solar cells based on organic semiconductors has been widely used to achieve a better match to the solar irradiance spectrum, and power conversion effciencies beyond 10% have been reported. However, the fill factor of organic solar cells is still limited by the competition between recombination and extraction of free charges. Here, we design advanced material composites leading to a high fill factor of 77% in ternary blends, thus demonstrating how the recombination thresholds can be overcome. Extending beyond the typical sensitization concept, we add a highly ordered polymer that, in addition to enhanced absorption, overcomes limits predicted by classical recombination models. An effective charge transfer from the disordered host system onto the highly ordered sensitizer effectively avoids traps of the host matrix and features an almost ideal recombination behaviour.},
author = {Gasparini, Nicola and Jiao, Xuechen and Heumüller, Thomas and Baran, Derya and Matt, Gebhard and Fladischer, Stefanie and Spiecker, Erdmann and Ade, Harald and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.1038/NENERGY.2016.118},
faupublication = {yes},
journal = {Nature Energy},
peerreviewed = {Yes},
title = {{Designing} ternary blend bulk heterojunction solar cells with reduced carrier recombination and a fill factor of 77%},
volume = {1},
year = {2016}
}
@article{faucris.120960664,
abstract = {Length of the terminal alkyl chains at dicyanovinyl (DCV) groups of two dithienosilole (DTS) containing small molecules (DTS(Oct)2-(2T-DCV-Me)2 and DTS(Oct)2-(2T-DCV-Hex)2) is investigated to evaluate how this affects the molecular solubility and blend morphology as well as their performance in bulk heterojunction organic solar cells (OSCs). While the DTS(Oct)2-(2T-DCV-Me)2 (a solubility of 5 mg mL-1) system exhibits both high short circuit current density (J sc) and high fill factor, the DTS(Oct)2-(2T-DCV-Hex)2 (a solubility of 24 mg mL-1) system in contrast suffers from a poor blend morphology as examined by atomic force morphology and grazing incidence X-ray scattering measurements, which limit the photovoltaic properties. The charge generation, transport, and recombination dynamics associated with the limited device performance are investigated for both systems. Nongeminate recombination losses in DTS(Oct)2-(2T-DCV-Hex)2 system are demonstrated to be significant by combining space charge limited current analysis and light intensity dependence of current-voltage characteristics in combination with photogenerated charge carrier extraction by linearly increasing voltage and transient photovoltage measurements. DTS(Oct)2-(2T-DCV-Me)2 in contrast performs nearly ideal with no evidence of nongeminate recombination, space charge effects, or mobility limitation. These results demonstrate the importance of alkyl chain engineering for solution-processed OSCs based on small molecules as an essential design tool to overcome transport limitations.},
author = {Min, Jie and Luponosov, Yuriy N. and Gasparini, Nicola and Richter, Moses and Bakirov, Artem V. and Shcherbina, Maxim A. and Chvalun, Sergei N. and Grodd, Linda and Grigorian, Souren and Ameri, Tayebeh and Ponomarenko, Sergei A. and Brabec, Christoph},
doi = {10.1002/aenm.201500386},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {blend morphology; molecular solubility; organic solar cells; recombination dynamics; transport limitations},
peerreviewed = {unknown},
title = {{Effects} of {Alkyl} {Terminal} {Chains} on {Morphology}, {Charge} {Generation}, {Transport}, and {Recombination} {Mechanisms} in {Solution}-{Processed} {Small} {Molecule} {Bulk} {Heterojunction} {Solar} {Cells}},
volume = {5},
year = {2015}
}
@article{faucris.109391524,
abstract = {Optoelectronic properties, supramolecular assemblies, and morphology variation of polymeric semiconductors are governed by six fundamental chemical features. These features are molecular weight, bond length alternation (BLA), planarity, aromatic resonance energy, substituents, and intermolecular interactions. Of these features the specific role of BLA in determining the performance of a polymeric semiconductor in practical technological applications is so far unknown. This study investigates this question and reports the novel finding that the optoelectronic, microscopic (supramolecular packing), and macroscopic (morphology variation and device performance) properties of model semiconducting polymers depend on the conjugated polymer backbone enlargement, which is directly related to the BLA. Extensive studies are performed in both single-component polymer films and their blends with fullerene derivatives. Understanding the specific structure-properties relations will lead to significant advancement in the area of organic electronics, since it will set new design rules toward further optimization of polymer chemical structures to enhance the device performances. An efficient way to enlarge the polymer backbone of an electron donor conjugated polymer toward higher organic photovoltaic performance is presented.},
author = {Chochos, Christos L. and Singh, Ranbir and Kim, Min and Gasparini, Nicola and Katsouras, Athanasios and Kulshreshtha, Chandramouli and Gregoriou, Vasilis G. and Keivanidis, Panagiotis E. and Ameri, Tayebeh and Brabec, Christoph and Cho, Kilwon and Avgeropoulos, Apostolos},
doi = {10.1002/adfm.201504953},
faupublication = {yes},
journal = {Advanced Functional Materials},
keywords = {morphology; organic electronics; polymer semiconductors; recombination dynamics; supramolecular assembly},
pages = {1840-1848},
peerreviewed = {unknown},
title = {{Enhancement} of the {Power} {Conversion} {Efficiency} in {Organic} {Photovoltaics} by {Unveiling} the {Appropriate} {Polymer} {Backbone} {Enlargement} {Approach}},
volume = {26},
year = {2016}
}
@article{faucris.123726724,
abstract = {Perovskite solar cells based on CHNHPbBr with a band gap of 2.3 eV are attracting intense research interests due to their high open-circuit voltage (V) potential, which is specifically relevant for the use in tandem configuration or spectral splitting. Many efforts have been performed to optimize the V of CHNHPbBr solar cells; however, the limiting V (namely, radiative V:V) and the corresponding ΔV (the difference between V and V) mechanism are still unknown. Here, the average V of 1.50 V with the maximum value of 1.53 V at room temperature is achieved for a CHNHPbBr solar cell. External quantum efficiency measurements with electroluminescence spectroscopy determine the V of CHNHPbBr cells with 1.95 V and a ΔV of 0.45 V at 295 K. When the temperature declines from 295 to 200 K, the obtained V remains comparably stable in the vicinity of 1.5 V while the corresponding ΔV values show a more significant increase. Our findings suggest that the V of CHNHPbBr cells is primarily limited by the interface losses induced by the charge extraction layer rather than by bulk dominated recombination losses. These findings are important for developing strategies how to further enhance the V of CHNHPbBr-based solar cells.},
author = {Chen, Shi and Hou, Yi and Chen, Haiwei and Richter, Moses and Guo, Fei and Kahmann, Simon and Tang, Xiaofeng and Stubhan, Tobias and Zhang, Hong and Li, Ning and Gasparini, Nicola and Ramírez Quiroz, César Omar and Khanzada, Laraib Sarfraz and Matt, Gebhard and Osvet, Andres and Brabec, Christoph},
doi = {10.1002/aenm.201600132},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {CH3NH3PbBr3 solar cells; interface materials based losses; nonradiative recombination losses; open-circuit voltage},
peerreviewed = {unknown},
title = {{Exploring} the {Limiting} {Open}-{Circuit} {Voltage} and the {Voltage} {Loss} {Mechanism} in {Planar} {CH3NH3PbBr3} {Perovskite} {Solar} {Cells}},
volume = {6},
year = {2016}
}
@article{faucris.106799044,
abstract = {Solution-processed oxo-functionalized graphene (oxo-G) is employed to substitute hydrophilic PEDOT:PSS as an anode interfacial layer for perovskite solar cells. The resulting devices exhibit a reasonably high power conversion efficiency (PCE) of 15.2% in the planar inverted architecture with oxo-G as a hole transporting material (HTM), and most importantly, deploy the full open-circuit voltage (V) of up to 1.1 V. Moreover, oxo-G effectively slows down the ingress of water vapor into the device stack resulting in significantly enhanced environmental stability of unpackaged cells under illumination with 80% of the initial PCE being reached after 500 h. Without encapsulation, ∼60% of the initial PCE is retained after ∼1000 h of light soaking under 0.5 sun and ambient conditions maintaining the temperature beneath 30 °C. Moreover, the unsealed perovskite device retains 92% of its initial PCE after about 1900 h under ambient conditions and in the dark. Our results underpin that controlling water diffusion into perovskite cells through advanced interface engineering is a crucial step towards prolonged environmental stability.},
author = {Chen, Haiwei and Hou, Yi and Halbig, Christian Eberhard and Chen, Shi and Zhang, Hong and Li, Ning and Guo, Fei and Tang, Xiaofeng and Gasparini, Nicola and Levchuk, Ievgen and Kahmann, Simon and Ramírez Quiroz, César Omar and Osvet, Andres and Eigler, Siegfried and Brabec, Christoph},
doi = {10.1039/c6ta03755k},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
keywords = {Engineering controlled terms: Cell engineering; Conducting polymers; Open circuit voltage; Perovskite; Slow light; Solar cells Environmental stability; Functionalized graphene; High power conversion; Hole-transporting materials; Interface engineering; Interfacial design; Inverted architectures; Solution-processed Engineering main heading: Perovskite solar cells},
pages = {11604-11610},
peerreviewed = {unknown},
title = {{Extending} the environmental lifetime of unpackaged perovskite solar cells through interfacial design},
volume = {4},
year = {2016}
}
@article{faucris.216716217,
abstract = {Ternary
blends with broad spectral absorption have the potential to increase charge
generation in organic solar cells but feature additional complexity due to
limited intermixing and electronic mismatch. Here, a model system comprising
the polymers poly[5,5-bis(2-butyloctyl)-(2,2-bithiophene)-4,4-dicarboxylate-alt-5,5-2,2-bithiophene]
(PDCBT) and PTB7-Th and PC70BM as an electron
accepting unit is presented. The power conversion efficiency (PCE) of the
ternary system clearly surpasses the performance of either of the binary systems.
The photophysics is governed by a fast energy transfer process from PDCBT to
PTB7-Th, followed by electron transfer at the PTB7-Th:fullerene interface. The
morphological motif in the ternary blend is characterized by polymer fibers.
Based on a combination of photophysical analysis, GIWAXS measurements and
calculation of the intermolecular parameter, the latter indicating a very
favorable molecular affinity between PDCBT and PTB7-Th, it is proposed that an
efficient charge generation mechanism is possible because PTB7-Th predominantly
orients around PDCBT filaments, allowing energy to be effectively relayed from
PDCBT to PTB7-Th. Fullerene can be replaced by a nonfullerene acceptor without
sacrifices in charge generation, achieving a PCE above 11%. These results
support the idea that thermodynamic mixing and energetics of the polymer–polymer
interface are critical design parameter for realizing highly efficient ternary
solar cells with variable electron acceptors
uncommonly thick active layer (>300 nm),
featuring thickness invariant charge carrier recomb
ination and delivering 11% power
conversion efficiency (PCE). The ternary blend was
used to demonstrate photovoltaic
modules of high technological relevance both on gla
ss and flexible substrates, yielding 8.2%
and 6.8% PCE, respectively.},
author = {Gasparini, Nicola and Lucera, Luca and Salvador, Michael Filipe and Prosa, Mario and Spyropoulos, Georgios and Kubis, Peter and Egelhaaf, Hans Joachim and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.1039/C6EE03599J},
faupublication = {yes},
journal = {Energy and Environmental Science},
pages = {885-892},
peerreviewed = {unknown},
title = {{High} performance ternary organic solar cells with thick active layer exceeding 11% efficiency},
url = {http://pubs.rsc.org/en/content/articlepdf/2017/ee/c6ee03599j},
volume = {10},
year = {2017}
}
@article{faucris.205676387,
abstract = {Here, brand new ternary hybrid solar cells comprising perovskite nanocrystals (NCs) with a complementary absorption profile of the organic host matrix are reported. In particular, NH2CHNH2PbI3 (FAPbI3) perovskite NCs are implemented in bulk heterojunction organic solar cells based on the pDPP5T-2 electron donating polymer and a [6,6]-phenyl-C61-butyric acid methyl ester (PC61BM) acceptor at various loading amounts and the fabricated hybrid
photovoltaics are thoroughly studied by employing different
optoelectrical characterization methods. Current-voltage measurements
and photoinduced charge carrier extraction by linear increasing voltage (photo-CELIV) reveal improved charge generation and charge transport properties upon incorporation of perovskite NCs into the photo-active layer of the hybrid solar cell. The power conversion efficiency (PCE) of the hybrid solar cell comprising 5% perovskite
NCs is 10% enhanced compared to the organic reference, mainly due to
the enlarged light harvesting and increased short circuit current
density (Jsc). However, results suggest that introducing a higher amount of perovskite content induces bimolecular and trap-assisted recombination in the ternary devices. We perform a comprehensive transient absorption study of the charge
transfer/transport mechanisms by employing femto-second pump-probe
transient absorption spectroscopy (fs-TAS). fs-TAS measurements
demonstrate a slower charge carrier recombination rate due to the introduction of perovskite NCs into the photoactive layer. Results reveal that DPP injects electrons from the singlet excited state into the perovskite NCs, which causes the desired cascading charge carrier transfer. In ternary blends, a small amount of FAPbI3 NCs provides an additional pathway in favor of the charge-separated
state via the NCs, which, despite accelerating the depopulation of
DPP's singlet excited state slightly slows down the charge-separation process between DPP and PC61BM. Interestingly, the loss processes are slowed down; an effect that is more important and, hence, explains the improved solar cell efficiency. © 2018 the Owner Societie},
author = {Soltani, Rezvan and Puscher, Bianka and Katbab, Ali Asghar and Levchuk, Ievgen and Kazerouni, Negar and Gasparini, Nicola and Camaioni, Nadia and Osvet, Andres and Batentschuk, Miroslaw and Fink, Rainer and Guldi, Dirk Michael and Ameri, Tayebeh},
doi = {10.1039/c8cp03743d},
faupublication = {yes},
journal = {Physical Chemistry Chemical Physics},
pages = {23674-23683},
peerreviewed = {Yes},
title = {{Improved} charge carrier dynamics in polymer/perovskite nanocrystal based hybrid ternary solar cells},
volume = {20},
year = {2018}
}
@article{faucris.122800304,
abstract = {One of the key aspects to achieve high efficiency in ternary bulk-hetorojunction solar cells is the physical and chemical compatibility between the donor materials. Here, we report the synthesis of a novel conjugated polymer (P1) containing alternating pyridyl[2,1,3]thiadiazole between two different donor fragments, dithienosilole and indacenodithienothiophene (IDTT), used as a sensitizer in a host system of indacenodithieno[3,2-b]thiophene,2,3-bis(3-(octyloxy)phenyl)quinoxaline (PIDTTQ) and [6,6]-phenyl C70 butyric acid methyl ester (PC71BM). We found that the use of the same IDTT unit in the host and guest materials does not lead to significant changes in the morphology of the ternary blend compared to the host binary. With the complementary use of optoelectronic characterizations, we found that the ternary cells suffer from a lower mobility-lifetime (μτ) product, adversely impacting the fill factor. However, the significant light harvesting in the near infrared region improvement, compensating the transport losses, results in an overall power conversion efficiency enhancement of ~7% for ternary blends as compared to the PIDTTQ:PC71BM devices.},
author = {Gasparini, Nicola and García-Rodríguez, Amaranda and Prosa, Mario and Bayseç, Sebnem and Cando, Alex Palma and Katsouras, Athanasios and Avgeropoulos, Apostolos and Pagona, Georgia and Gregoriou, Vasilis G. and Chochos, Christos L. and Allard, Sybille and Scherf, Ullrich and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.3389/fenrg.2016.00040},
faupublication = {yes},
journal = {Frontiers in Energy Research},
keywords = {organic solar cells, ternary devices, OPV, IDTT, organic electronics},
month = {Jan},
peerreviewed = {Yes},
title = {{Indacenodithienothiophene}-{Based} {Ternary} {Organic} {Solar} {Cells}},
url = {https://www.frontiersin.org/articles/10.3389/fenrg.2016.00040/full},
volume = {4},
year = {2017}
}
@inproceedings{faucris.234066281,
abstract = {Using broadband transient absorption in a high efficiency (>11%)
photovoltaic blend with a non-fullerene acceptor, we observe
instantaneous (sub-30 fs) charge separation, demonstrating close to
ideal donor-acceptor level matching and nanomorphology in this ble},
author = {Franco, V. A. Camargo and Gasparini, Nicola and Nagahara, Tetsuhiko and Lueer, Larry and Cerullo, Giulio and Brabec, Christoph},
booktitle = {205},
date = {2018-07-15/2018-07-20},
doi = {10.1051/epjconf/201920505010},
faupublication = {yes},
peerreviewed = {unknown},
title = {{Instantaneous} charge separation in non-fullerene acceptor bulk-heterojunction of highly efficient solar cells},
venue = {Hamburg},
year = {2019}
}
@article{faucris.119894324,
abstract = {The synthesis of a series of A-π-D-π-A oligomers bearing coplanar electron-donating dithieno[3,2-b:2′,3′-d]silole (DTS) unit linked through bithiophene π-bridges with the electron-withdrawing alkyldicyanovinyl (alkyl-DCV) groups is described. This study demonstrates a systematic investigation of structure-property relationships in this type of oligomer and shows obvious benefits of alkyl-DCV groups as compared to the commonly used DCV ones, in terms of elaboration of high performance organic solar cells (OSCs). Considerable efforts have been made to improve the power conversion efficiency (PCE) of oligomer-based OSCs by diverse strategies including fine-tuning of the oligomer properties via variation of their terminal and central alkyl chains, blend morphology control via solvent vapor annealing (SVA) treatment, and surface modification via interfacial engineering. These efforts allowed achieving PCEs of up to 6.4% for DTS(Oct)-(2T-DCV-Me) blended with PCBM. Further morphological investigations demonstrated that the usage of SVA treatment indeed effectively results in increased absorption and ordering of the BHJ composite, with the only exception for the most soluble oligomer DTS(Oct)-(2T-DCV-Hex). Besides, a detailed study analyzed the charge transport properties and recombination loss mechanisms for these oligomers. This study not only revealed the importance of integrated alkyl chain engineering on gaining morphological control for high performance OSCs, but also exhibited a clear correlation between molecular ordering and charge carrier mobility respective to carrier dynamics. These results outline a detailed strategy towards a rather complete characterization and optimization methodology for organic photovoltaic devices, thereby paving the way for researchers to easily find the performance parameters adapted for widespread applications.},
author = {Min, Jie and Luponosov, Yuriy N. and Gasparini, Nicola and Xue, Lingwei and Drozdov, Fedor V. and Peregudova, Svetlana M. and Dmitryakov, Petr V. and Gerasimov, Kirill L. and Anokhin, Denis V. and Zhang, Zhi-Guo and Ameri, Tayebeh and Chvalun, Sergei N. and Ivanov, Dimitri A. and Li, Yongfang and Ponomarenko, Sergei A. and Brabec, Christoph},
doi = {10.1039/c5ta06706e},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
keywords = {Engineering controlled terms: Cell engineering; Oligomers; Surface treatment; Varactors Electronwithdrawing; Morphological control; Optimization methodology; Organic photovoltaic devices; Performance parameters; Power conversion efficiencies; Solvent-vapor annealing; Structure property relationships Engineering main heading: Solar cells},
pages = {22695-22707},
peerreviewed = {unknown},
title = {{Integrated} molecular, morphological and interfacial engineering towards highly efficient and stable solution-processed small molecule solar cells},
volume = {3},
year = {2015}
}
@article{faucris.107432424,
abstract = {Hybrid solar cells based on the pDPP5T-2 electron donating polymer, [6,6]-phenyl-C-butyric acid methyl ester (PCBM) and cadmium selenide telluride (CdSeTe) quantum dots (QDs) are fabricated and their photovoltaic performance and optoelectronic properties are investigated as a function of QD loading. The power conversion efficiency (PCE) of hybrid solar cells is improved up to 5.11% for the device containing 4 wt% of QDs which is mainly due to the enhancement in short circuit current density (J) resulting from increased light harvesting. A full-fledged study is performed on the microstructure, charge transfer/transport and recombination mechanisms of our ternary hybrid solar cells by employing various advanced techniques. The transmission electron microscopy (TEM) results reveal the non-agglomerated and uniform distribution of the CdSeTe QDs within the pDPP5T-2:PCBM host matrix at low QD concentrations. Transient absorption spectroscopy (TAS) showed a slower charge carrier recombination rate due to the introduction of QDs into the photoactive layer. It can be attributed to the more efficient exciton dissociation in ternary systems. These findings are consistent with the photovoltaic properties of the device.},
author = {Soltani, Rezvan and Katbab, Ali Asghar and Schaumberger, Kerstin and Gasparini, Nicola and Brabec, Christoph and Rechberger, Stefanie and Spiecker, Erdmann and Alabau, Antoni Gimeno and Ruland, Andres and Saha, Avishek and Guldi, Dirk Michael and Sgobba, Vito and Ameri, Tayebeh},
doi = {10.1039/c6tc04308a},
faupublication = {yes},
journal = {Journal of Materials Chemistry C},
keywords = {Engineering controlled terms: Absorption spectroscopy; Butyric acid; Cadmium compounds; Cadmium telluride; Charge transfer; Heterojunctions; High resolution transmission electron microscopy; Nanocrystals; Polymer solar cells; Semiconductor quantum dots; Solar power generation; Transmission electron microscopy Bulk heterojunction solar cells; Charge carrier recombination; Light harvesting enhancement; Optoelectronic properties; Photovoltaic performance; Power conversion efficiencies; Recombination mechanisms; Transient absorption spectroscopies Engineering main heading: Solar cells},
pages = {654-662},
peerreviewed = {Yes},
title = {{Light} harvesting enhancement upon incorporating alloy structured {CdSeXTe1}−{X} quantum dots in {DPP}:{PC61BM} bulk heterojunction solar cells},
volume = {5},
year = {2017}
}
@article{faucris.106819064,
abstract = {The production of high-performance, solution-processed kesterite Cu2ZnSn(Sx,Se1-x)4 (CZTSSe) solar cells typically relies on high-temperature crystallization processes in chalcogen-containing atmosphere and often on the use of environmentally harmful solvents, which could hinder the widespread adoption of this technology. We report a method for processing selenium free Cu2ZnSnS4 (CZTS) solar cells based on a short annealing step at temperatures as low as 350 °C using a molecular based precursor, fully avoiding highly toxic solvents and high-temperature sulfurization. We show that a simple device structure consisting of ITO/CZTS/CdS/Al and comprising an extremely thin absorber layer (∼110 nm) achieves a current density of 8.6 mA/cm2. Over the course of 400 days under ambient conditions encapsulated devices retain close to 100% of their original efficiency. Using impedance spectroscopy and photoinduced charge carrier extraction by linearly increasing voltage (photo-CELIV), we demonstrate that reduced charge carrier mobility is one limiting parameter of low-temperature CZTS photovoltaics. These results may inform less energy demanding strategies for the production of CZTS optoelectronic layers compatible with large-scale processing techniques.},
author = {Hou, Yi and Azimi, Seyed Hamed and Gasparini, Nicola and Savador, Michael and Chen, Wei and Khanzada, Laraib Sarfraz and Brandl, Marco and Hock, Rainer and Brabec, Christoph},
doi = {10.1021/acsami.5b04468},
faupublication = {yes},
journal = {ACS Applied Materials and Interfaces},
keywords = {CZTS; device stability; kesterite solar cells; low-temperature processing; molecular based precursor},
pages = {21100-21106},
peerreviewed = {unknown},
title = {{Low}-{Temperature} {Solution}-{Processed} {Kesterite} {Solar} {Cell} {Based} on in {Situ} {Deposition} of {Ultrathin} {Absorber} {Layer}},
volume = {7},
year = {2015}
}
@article{faucris.123734644,
abstract = {We demonstrate an innovative solution-processing fabrication route for organic and perovskite solar modules via depth-selective laser patterning of an adhesive top electrode. This yields unprecedented power conversion efficiencies of up to 5.3% and 9.8%, respectively. We employ a PEDOT:PSS-Ag nanowire composite electrode and depth-resolved post-patterning through beforehand laminated devices using ultra-fast laser scribing. This process affords low-loss interconnects of consecutive solar cells while overcoming typical alignment constraints. Our strategy informs a highly simplified and universal approach for solar module fabrication that could be extended to other thin-film photovoltaic technologies.},
author = {Spyropoulos, George D. and Quiroz, Cesar Omar Ramirez and Salvador, Michael Filipe and Hou, Yi and Gasparini, Nicola and Schweizer, Peter and Adams, Jens and Kubis, Peter and Li, Ning and Spiecker, Erdmann and Ameri, Tayebeh and Egelhaaf, Hans-Joachim and Brabec, Christoph},
doi = {10.1039/c6ee01555g},
faupublication = {yes},
journal = {Energy and Environmental Science},
keywords = {Indexed keywords Engineering controlled terms: Conducting polymers; Electrodes; Laminated composites; Organic lasers; Perovskite; Solar cells; Solar power generation Depth-resolved; Fabrication routes; Innovative solutions; Laser patterning; Photovoltaic technology; Power conversion efficiencies; Solar module; Universal approach Engineering main heading: Solar cell arrays GEOBASE Subject Index: efficiency measurement; electrode; film; innovation; laser method; perovskite; photovoltaic system},
pages = {2302-2313},
peerreviewed = {unknown},
title = {{Organic} and perovskite solar modules innovated by adhesive top electrode and depth-resolved laser patterning},
volume = {9},
year = {2016}
}
@article{faucris.204905528,
author = {Strohm, S. and Machui, F. and Langner, Stefan and Kubis, P. and Gasparini, Nicola and Salvador, Michael Filipe and Mcculloch, I. and Egelhaaf, H. -J. and Brabec, Christoph},
doi = {10.1039/c8ee01150h},
faupublication = {yes},
journal = {Energy and Environmental Science},
pages = {2225-2234},
peerreviewed = {Yes},
title = {{P3HT}: {Non}-fullerene acceptor based large area, semi-transparent {PV} modules with power conversion efficiencies of 5%, processed by industrially scalable methods},
volume = {11},
year = {2018}
}
@article{faucris.122587344,
abstract = {More efficient light harvesting throughout the whole solar spectrum by introducing third and fourth components offers a new pathway towards the development of high efficiency organic solar cells based on polymer/fullerene blends. Recently, dye molecules have been utilized as promising light harvesting photosensitizers in the near-IR region. Herein, we report the design, synthesis and application of a novel silicon naphthalocyanine (SiNC-1) as an efficient photosensitizer in single dye ternary devices as well as in multi-colored co-sensitized quaternary devices, incorporating a silicon phthalocyanine (SiPC-0 or SiPC-1) as the fourth component to complement the spectral absorption of the SiNC-1. The dominant complex charge transfer/transport mechanism behind the enhanced photosensitivity of the ternary blend has been investigated by means of electrical, optical, and advanced characterization techniques. External quantum efficiency (EQE) measurements on multi-colored dye sensitized devices covering the UV-vis as well as near-IR regions from 350 up to 900 nm outline apparent signal characteristics of each single dye, corroborating the effective contribution of both SiPC and SiNC dyes to enhancing the short-circuit current density (J). Our results further illustrate the potential of the multi-colored dye sensitization concept as a powerful approach to mitigate the non-ideal optical absorption normally encountered in organic-based optoelectronic devices.},
author = {Ke, Lili and Gasparini, Nicola and Min, Jie and Zhang, Hong and Adam, Matthias and Rechberger, Stefanie and Forberich, Karen and Zhang, Chaohong and Spiecker, Erdmann and Tykwinski, Rik and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.1039/c6ta08729a},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
keywords = {Engineering controlled terms: Charge transfer; Dye-sensitized solar cells; Efficiency; Electromagnetic wave absorption; Light absorption; Nitrogen compounds; Optoelectronic devices; Organic solar cells; Photosensitizers; Polymer blends; Polymer solar cells; Silicon; Solar cells Characterization techniques; Dye sensitization; External quantum efficiency; Light-harvesting; Naphthalocyanines; Phthalocyanine dyes; Signal characteristic; Spectral absorptions Engineering main heading: Silicon solar cells},
pages = {2550-2562},
peerreviewed = {unknown},
title = {{Panchromatic} ternary/quaternary polymer/fullerene {BHJ} solar cells based on novel silicon naphthalocyanine and silicon phthalocyanine dye sensitizers},
volume = {5},
year = {2017}
}
@article{faucris.119528244,
abstract = {The photovoltaic performance and optoelectronic properties of a donor-acceptor copolymer are reported based on indacenodithienothiophene (IDTT) and 2,3-bis(3-(octyloxy)phenyl)quinoxaline moieties (PIDTTQ) as a function of the number-average molecular weight (Mn). Current-voltage measurements and photoinduced charge carrier extraction by linear increasing voltage (photo-CELIV) reveal improved charge generation and charge transport properties in these high band gap systems with increasing Mn, while polymers with low molecular weight suffer from diminished charge carrier extraction because of low mobility-lifetime (μτ) product. By combining Fourier-transform photocurrent spectroscopy (FTPS) with electroluminscence spectroscopy, it is demonstrate that increasing Mn reduces the nonradiative recombination losses. Solar cells based on PIDTTQ with Mn = 58 kD feature a power conversion efficiency of 6.0% and a charge carrier mobility of 2.1 × 10-4 cm2 V-1 s-1 when doctor bladed in air, without the need for thermal treatment. This study exhibits the strong correlations between polymer fractionation and its optoelectronics characteristics, which informs the polymer design rules toward highly efficient organic solar cells.},
author = {Gasparini, Nicola and Katsouras, Athanasios and Prodromidis, Mamantos I. and Avgeropoulos, Apostolos and Baran, Derya and Salvador, Michael Filipe and Fladischer, Stefanie and Spiecker, Erdmann and Chochos, Christos L. and Ameri, Tayebeh and Brabec, Christoph},
doi = {10.1002/adfm.201501062},
faupublication = {yes},
journal = {Advanced Functional Materials},
keywords = {charge transport; energetic losses; indacenodithienothiophene; molecular weight; organic solar cells},
pages = {4898-4907},
peerreviewed = {Yes},
title = {{Photophysics} of {Molecular}-{Weight}-{Induced} {Losses} in {Indacenodithienothiophene}-{Based} {Solar} {Cells}},
volume = {25},
year = {2015}
}
@article{faucris.118128384,
abstract = {Organic semiconductors are in general known to have an inherently lower charge carrier mobility compared to their inorganic counterparts. Bimolecular recombination of holes and electrons is an important loss mechanism and can often be described by the Langevin recombination model. Here, the device physics of bulk heterojunction solar cells based on a nonfullerene acceptor (IDTBR) in combination with poly(3-hexylthiophene) (P3HT) are elucidated, showing an unprecedentedly low bimolecular recombination rate. The high fill factor observed (above 65%) is attributed to non-Langevin behavior with a Langevin prefactor (β/βL) of 1.9 × 10-4. The absence of parasitic recombination and high charge carrier lifetimes in P3HT:IDTBR solar cells inform an almost ideal bimolecular recombination behavior. This exceptional recombination behavior is explored to fabricate devices with layer thicknesses up to 450 nm without significant performance losses. The determination of the photoexcited carrier mobility by time-of-flight measurements reveals a long-lived and nonthermalized carrier transport as the origin for the exceptional transport physics. The crystalline microstructure arrangement of both components is suggested to be decisive for this slow recombination dynamics. Further, the thickness-independent power conversion efficiency is of utmost technological relevance for upscaling production and reiterates the importance of understanding material design in the context of low bimolecular recombination. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.},
author = {Gasparini, Nicola and Salvador, Michael Filipe and Heumüller, Thomas and Richter, Moses and Classen, Andrej and Shrestha, Shreetu and Matt, Gebhard and Holliday, Sarah and Strohm, Sebastian and Egelhaaf, Hans Joachim and Wadsworth, Andrew and Baran, Derya and Mcculloch, Iain and Brabec, Christoph},
doi = {10.1002/aenm.201701561},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {Charge recombination; Charge transport; Langevin; Nonfullerene acceptor; Organic photovoltaic devices},
peerreviewed = {unknown},
title = {{Polymer}: {Nonfullerene} {Bulk} {Heterojunction} {Solar} {Cells} with {Exceptionally} {Low} {Recombination} {Rates}},
year = {2017}
}
@article{faucris.106823904,
abstract = {Building integrated semitransparent thin-film solar cells is a strategy for future eco-friendly power generation. Organic photovoltaics in combination with dielectric mirrors (DMs) are a potential candidate as they promise high efficiencies in parallel to the possibility to adjust the color and thus the transparency of the whole device. A fully solution processed and printable DM with an easily adjustable reflection maximum is presented that can be facilely attached to solar cells. The DM is optimized via optical simulations to the particular needs of the device with regard to photocurrent enhancement. The excellent agreement between experimental and theoretical results confirms the high optical quality of the printed layers with respect to homogeneity and surface roughness. The used inks are organic-inorganic nanocomposites with a large refractive index contrast of ≈0.7. The short-circuit current is enhanced by up to ≈24% for a semitransparent polymer solar cell.},
author = {Bronnbauer, Carina and Hornich, Julian and Gasparini, Nicola and Guo, Fei and Hartmeier, Benjamin and Luechinger, Norman A. and Pflaum, Christoph and Brabec, Christoph and Forberich, Karen},
doi = {10.1002/adom.201500216},
faupublication = {yes},
journal = {Advanced Optical Materials},
keywords = {Dielectric mirrors; Organic photovoltaics; Printing; Refractive indices; Semitransparent},
pages = {1424-1430},
peerreviewed = {Yes},
title = {{Printable} {Dielectric} {Mirrors} with {Easily} {Adjustable} and {Well}-{Defined} {Reflection} {Maxima} for {Semitransparent} {Organic} {Solar} {Cells}},
volume = {3},
year = {2015}
}
@article{faucris.107232664,
abstract = {Systematic optimization of the chemical structure of wide-bandgap (≈2.0 eV) "donor-acceptor" copolymers consisting of indacenodithiophene or indacenodithieno[3,2-b]thiophene as the electron-rich unit and thieno[3,4-c]pyrrole-4,6-dione as the electron-deficient moiety in terms of alkyl side chain engineering and distance of the electron-rich and electron-deficient monomers within the repeat unit of the polymer chain results in high-performance electron donor materials for organic photovoltaics. Specifically, preliminary results demonstrate extremely high open circuit voltages (V s) of ≈1.0 V, reasonable short circuit current density (J ) of around 11 mA cm, and moderate fill factors resulting in efficiencies close to 6%. All the devices are fabricated in an inverted architecture with the photoactive layer processed by doctor blade equipment, showing the compatibility with roll-to-roll large-scale manufacturing processes. From the correlation of the chemical structure-optoelectronic properties-photovoltaic performance, a rational guide toward further optimization of the chemical structure in this family of copolymers, has been achieved.},
author = {Chochos, Christos L. and Katsouras, Athanasios and Gasparini, Nicola and Koulogiannis, Chrysanthos and Ameri, Tayebeh and Brabec, Christoph and Avgeropoulos, Apostolos},
doi = {10.1002/marc.201600614},
faupublication = {yes},
journal = {Macromolecular Rapid Communications},
keywords = {High open circuit voltage; Indacenodithiophene; Organic photovoltaics; Ternary solar cells; Wide-bandgap conjugated polymers},
peerreviewed = {unknown},
title = {{Rational} {Design} of {High}-{Performance} {Wide}-{Bandgap} (≈2 {eV}) {Polymer} {Semiconductors} as {Electron} {Donors} in {Organic} {Photovoltaics} {Exhibiting} {High} {Open} {Circuit} {Voltages} (≈1 {V})},
year = {2016}
}
@article{faucris.122574364,
abstract = {Optimization of the energy levels at the donor-acceptor interface of organic solar cells has driven their efficiencies to above 10%. However, further improvements towards efficiencies comparable with inorganic solar cells remain challenging because of high recombination losses, which empirically limit the open-circuit voltage (V) to typically less than 1 V. Here we show that this empirical limit can be overcome using non-fullerene acceptors blended with the low band gap polymer PffBT4T-2DT leading to efficiencies approaching 10% (9.95%). We achieve V up to 1.12 V, which corresponds to a loss of only E/q - V = 0.5 ± 0.01 V between the optical bandgap E of the polymer and V. This high V is shown to be associated with the achievement of remarkably low non-geminate and non-radiative recombination losses in these devices. Suppression of non-radiative recombination implies high external electroluminescence quantum efficiencies which are orders of magnitude higher than those of equivalent devices employing fullerene acceptors. Using the balance between reduced recombination losses and good photocurrent generation efficiencies achieved experimentally as a baseline for simulations of the efficiency potential of organic solar cells, we estimate that efficiencies of up to 20% are achievable if band gaps and fill factors are further optimized.},
author = {Baran, D. and Kirchartz, T. and Wheeler, S. and Dimitrov, S. and Abdelsamie, M. and Gorman, J. and Ashraf, R. S. and Holliday, S. and Wadsworth, A. and Gasparini, Nicola and Kaienburg, P. and Yan, H. and Amassian, A. and Brabec, Christoph and Durrant, J. R. and McCulloch, I.},
doi = {10.1039/c6ee02598f},
faupublication = {yes},
journal = {Energy and Environmental Science},
keywords = {Engineering controlled terms: Energy gap; Fullerenes; Open circuit voltage; Organic solar cells; Polymer solar cells; Timing circuits Donor-acceptor interfaces; Fullerene free; Inorganic solar cells; Low bandgap polymers; Non-radiative recombinations; Orders of magnitude; Photocurrent generations; Recombination loss Engineering main heading: Solar cells},
pages = {3783-3793},
peerreviewed = {unknown},
title = {{Reduced} voltage losses yield 10% efficient fullerene free organic solar cells with >1 {V} open circuit voltages},
volume = {9},
year = {2016}
}
@article{faucris.122070344,
abstract = {Technological deployment of organic photovoltaic modules requires improvements in device light-conversion efficiency and stability while keeping material costs low. Here we demonstrate highly efficient and stable solar cells using a ternary approach, wherein two non-fullerene acceptors are combined with both a scalable and affordable donor polymer, poly(3-hexylthiophene) (P3HT), and a high-efficiency, low-bandgap polymer in a single-layer bulk-heterojunction device. The addition of a strongly absorbing small molecule acceptor into a P3HT-based non-fullerene blend increases the device efficiency up to 7.7 ± 0.1% without any solvent additives. The improvement is assigned to changes in microstructure that reduce charge recombination and increase the photovoltage, and to improved light harvesting across the visible region. The stability of P3HT-based devices in ambient conditions is also significantly improved relative to polymer:fullerene devices. Combined with a low-bandgap donor polymer (PBDTTT-EFT, also known as PCE10), the two mixed acceptors also lead to solar cells with 11.0 ± 0.4% efficiency and a high open-circuit voltage of 1.03 ± 0.01 V.},
author = {Baran, Derya and Ashraf, Raja Shahid and Hanifi, David A. and Abdelsamie, Maged and Gasparini, Nicola and Röhr, Jason A. and Holliday, Sarah and Wadsworth, Andrew and Lockett, Sarah and Neophytou, Marios and Emmott, Christopher J M and Nelson, Jenny and Brabec, Christoph and Amassian, Aram and Salleo, Alberto and Kirchartz, Thomas and Durrant, James R. and McCulloch, Iain},
doi = {10.1038/nmat4797},
faupublication = {yes},
journal = {Nature Materials},
keywords = {Engineering controlled terms: Efficiency; Energy gap; Fullerenes; Heterojunctions; Molecules; Open circuit voltage; Photovoltaic cells; Polymer solar cells; Polymers; Solar power generation Ambient conditions; Bulk-heterojunction devices; Charge recombinations; Device efficiency; Low bandgap polymers; Organic photovoltaics; Poly-3-hexylthiophene; Solvent additives Engineering main heading: Solar cells},
pages = {363-369},
peerreviewed = {unknown},
title = {{Reducing} the efficiency–stability–cost gap of organic photovoltaics with highly efficient and stable small molecule acceptor ternary solar cells},
volume = {16},
year = {2016}
}
@article{faucris.121463364,
abstract = {The interconnection layer (ICL) of organic multijunction solar cells represents one of the most delicate parts to ensure an efficient device operation. In view of pushing the efficiencies toward the theoretical limit, the individuation of minor losses affecting the ICL operation is of crucial importance. However, the difficulties arising from its position within the complex device structure typically hamper an accurate and selective investigation of the ICL. Here, a method based on the analysis of the photo-generated current density-voltage (Jph-V) response of solar cells, in the region of bias over the open-circuit voltage, is proved to individuate minor electrical losses within the ICL. Interestingly, the proposed method is demonstrated to effectively operate on tandem substructures, where different ICLs are investigated through the combination of materials having diverse characteristics. Furthermore, the use of a complementary investigation technique based on electroluminescence (EL) analysis allows to distinguish the specific nature of the electrical losses. The combination of Jph-V and EL analyses represents an elegant and advanced approach to shed light on the quality of ICLs in tandem substructures by avoiding the fabrication of the more complex tandem architecture. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.},
author = {Prosa, Mario and Li, Ning and Gasparini, Nicola and Bolognesi, Margherita and Seri, Mirko and Muccini, Michele and Brabec, Christoph},
doi = {10.1002/admi.201700776},
faupublication = {yes},
journal = {Advanced Materials Interfaces},
keywords = {Electrical losses; Electroluminescence; Interconnecting layers; Organic tandem solar cells; Photo-generated current},
peerreviewed = {Yes},
title = {{Revealing} {Minor} {Electrical} {Losses} in the {Interconnecting} {Layers} of {Organic} {Tandem} {Solar} {Cells}},
year = {2017}
}
@article{faucris.119130924,
abstract = {Nonradiative recombination reduces the open-circuit voltage relative to its theoretical limit and leads to reduced luminescence emission at a given excitation. Therefore, it is possible to correlate changes in luminescence emission with changes in open-circuit voltage and in the charge carrier lifetime. Here we use luminescence studies combined with transient photovoltage and differential charging analyses to study the effect of polymer fractionation in indacenoedithiophene-co-benzothiadiazole (IDTBT):fullerene solar cells. In this system, polymer fractionation increases electroluminescence emission at the same injection current and reduces nonradiative recombination. High-molecular-weight and fractionated IDTBT polymers exhibit higher carrier lifetime-mobility product compared to that of their nonfractionated analogues, resulting in improved solar cell performance. (Graph Presented).},
author = {Baran, Derya and Vezie, Michelle S. and Gasparini, Nicola and Deledalle, Florent and Yao, Jizhong and Schroeder, Bob C. and Bronstein, Hugo and Ameri, Tayebeh and Kirchartz, Thomas and Mcculloch, Iain and Nelson, Jenny and Brabec, Christoph},
doi = {10.1021/acs.jpcc.5b05709},
faupublication = {yes},
journal = {Journal of Physical Chemistry C},
keywords = {Engineering controlled terms: Carrier lifetime; Charge carriers; Fullerenes; Light; Luminescence; Open circuit voltage; Polymers Differential charging; Electroluminescence emission; High molecular weight; Luminescence emission; Non-radiative recombinations; Polymer fractionation; Solar cell performance; Transient photovoltage Engineering main heading: Solar cells},
pages = {19668-19673},
peerreviewed = {unknown},
title = {{Role} of {Polymer} {Fractionation} in {Energetic} {Losses} and {Charge} {Carrier} {Lifetimes} of {Polymer}: {Fullerene} {Solar} {Cells}},
volume = {119},
year = {2015}
}
@article{faucris.123926044,
abstract = {Conjugated polymer semiconductors offer unique advantages over conventional semiconductors but tend to suffer from electro-optic performance roll-off, mainly due to reduced photofastness. Here, we demonstrate that the commodity nickel chelate nickel(ii) dibutyldithiocarbamate, Ni(dtc)2, effectively inhibits photooxidation across a wide range of prototypical π-conjugated polymer semiconductors and blends. The addition of 2-10 wt% of Ni(dtc)2 increases the resilience of otherwise quickly photobleaching semiconducting thin films, even in the presence of detrimental, radical forming processing additives. Using electron spin resonance spectroscopy and sensitive oxygen probes, we found that Ni(dtc)2 acts as a broadband stabilizer that inhibits both the formation of reactive radicals and singlet oxygen. The mechanism of stabilization is of sacrificial nature, but contains non-sacrificial contributions in polymers where singlet oxygen is a key driver of photooxidation. Ultrafast pump-probe spectroscopy reveals quenching of triplet excited states as the central mechanism of non-sacrificial stabilization. When introduced into the active layer of organic photovoltaic devices, Ni(dtc)2 retards the short circuit current loss in air without affecting the sensitive morphology of bulk heterojunctions and without major sacrifices in semiconductor properties. Antioxidants based on nickel complexes thus constitute functional stabilizers for elucidating degradation mechanisms in organic semiconductors and represent a cost-effective route toward organic electronic appliances with extended longevity. © 2017 The Royal Society of Chemistry.},
author = {Salvador, Michael and Gasparini, Nicola and Perea, Jose Dario and Paleti, Harish and Distler, Andreas and Inasaridze, Liana N. and Troshin, Pavel A. and Luer, Larry and Egelhaaf, Hans-Joachim and Brabec, Christoph},
doi = {10.1039/c7ee01403a},
faupublication = {yes},
journal = {Energy and Environmental Science},
keywords = {Engineering controlled terms: ChelationCost effectivenessDegradationElectron spin resonance spectroscopyHeterojunctionsMagnetic momentsNickelOxygenPhotobleachingPhotooxidationPolymer blendsProbesSemiconducting filmsSemiconductor devicesSpectroscopyStabilization Compendex keywords Degradation mechanismElectro-optic performanceOrganic electronicsOrganic photovoltaic devicesPolymer semiconductorsSemiconducting thin filmsSemiconductor propertiesUltrafast pump-probe spectroscopy Engineering main heading: Conjugated polymers},
pages = {2005-2016},
peerreviewed = {Yes},
title = {{Suppressing} photooxidation of conjugated polymers and their blends with fullerenes through nickel chelates},
volume = {10},
year = {2017}
}
@article{faucris.204907438,
abstract = {In this work, we present a novel small molecule based on
dithienylthienothiadiazole units (named SM1) acting as an efficient
component in ternary blend organic solar cells to modify the hole
extraction at the interface. Our findings show that the SM1 suppresses
the surface recombination and enhances the open-circuit voltage (Voc). By introducing SM1 in a host system composed of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM), we obtained Voc
values of up to 0.75 V and fill factors larger than 70% for the ternary
blends. As a consequence, the power conversion efficiency is improved
by about 30% compared to P3HT:PCBM binary devices. Interestingly,
external quantum efficiency and absorption spectra in the near-infrared
region do not show any contribution of SM1 in dried films. Instead, the
addition of the small molecule improves the Voc by
reducing the surface recombination losses. To shed light on the
recombination processes, we carried out Fourier-transform photocurrent
spectroscopy and impedance spectroscopy measurements. This work shows
that the ternary concept can also have functionalities other than
photosensitization and can even act as a morphology-directing agent or
an interface modifie},
author = {Galli, Diana and Gasparini, Nicola and Forster, Michael and Eckert, Anika and Widling, Christian and Killian, Manuela and Avgeropoulos, Apostolos and Gregoriou, Vasilis G. and Scherf, Ullrich and Chochos, Christos L. and Brabec, Christoph and Ameri, Tayebeh},
doi = {10.1021/acsami.8b09174},
faupublication = {yes},
journal = {ACS Applied Materials and Interfaces},
keywords = {open-circuit voltages; recombination losses; ternary organic solar cells; sensitizers; small molecules},
pages = {28803-28811},
peerreviewed = {unknown},
title = {{Suppressing} the {Surface} {Recombination} and {Tuning} the {Open}-{Circuit} {Voltage} of {Polymer}/{Fullerene} {Solar} {Cells} by {Implementing} an {Aggregative} {Ternary} {Compound}},
volume = {10},
year = {2018}
}
@article{faucris.108486884,
abstract = {Thin-film solar cell based on hybrid perovskites shows excellent light-to-power conversion efficiencies exceeding 22%. However, the mixed ionic-electronic semiconductor hybrid perovskite exhibits many unusual properties such as slow photocurrent instabilities, hysteresis behavior, and low-frequency giant capacitance, which still question us so far. This study presents a direct surface functionalization of transparent conductive oxide electrode with an ultrathin ≈2 nm thick phosphonic acid based mixed C60/organic self-assembled monolayer (SAM) that significantly reduces hysteresis. Moreover, due to the strong phosphonates bonds with indium tin oxide (ITO) substrates, the SAM/ITO substrates also exhibit an excellent recyclability merit from the perspective of cost effectiveness. Impedance studies find the fingerprint of an ion-based diffusion process in the millisecond to second regime for TiO2-based devices, which, however, is not observed for SAM-based devices at these low frequencies. It is experimentally demonstrated that ion migration can be considerably suppressed by carefully engineering SAM interfaces, which allows effectively suppressing hysteresis and unstable diode behavior in the frequency regime between ≈1 and 100 Hz. It is suggested that a reduced density of ionic defects in combination with the absence of charge carrier accumulation at the interface is the main physical origin for the reduced hysteresis.},
author = {Hou, Yi and Scheiner, Simon and Tang, Xiaofeng and Gasparini, Nicola and Richter, Moses and Li, Ning and Schweizer, Peter and Chen, Shi and Chen, Haiwei and Ramírez Quiroz, César Omar and Du, Xiaoyan and Matt, Gebhard and Osvet, Andres and Spiecker, Erdmann and Fink, Rainer and Hirsch, Andreas and Halik, Marcus and Brabec, Christoph},
doi = {10.1002/admi.201700007},
faupublication = {yes},
journal = {Advanced Materials Interfaces},
peerreviewed = {Yes},
title = {{Suppression} of {Hysteresis} {Effects} in {Organohalide} {Perovskite} {Solar} {Cells}},
url = {http://onlinelibrary.wiley.com/doi/10.1002/admi.201700007/abstract},
year = {2017}
}
@article{faucris.122777424,
abstract = {A novel main-chain polyfullerene, poly[fullerene-alt-2,5-bis(octyloxy)terephthalaldehyde] (PPC4), is investigated for its hypothesized superior morphological stability as an electron-accepting material in organic photovoltaics relative to the widely used fullerene phenyl-C61-butyric acid methyl ester (PCBM). When mixed with poly(3-hexylthiophene-2,5-diyl) (P3HT), PPC4 affords low-charge-generation yields because of poor intermixing within the blend. The adoption of a multiacceptor system, by introducing PCBM into the P3HT:polyfullerene blend, was found to lead to a 3-fold enhancement in charge generation, affording power conversion efficiencies very close to that of the prototypical P3HT:PCBM binary control. Upon thermal stressing and in contrast to the P3HT:PCBM binary, photovoltaic devices based on the multiacceptor system demonstrated significantly improved stability, outperforming the control because of suppression of the PCBM migration and aggregation processes responsible for rapid device failure. We rationalize the influence of the fullerene miscibility and its implications on the device performance in terms of a thermodynamic model based on Flory-Huggins solution theory. Finally, the potential universal applicability of this approach for thermal stabilization of organic solar cells is demonstrated, utilizing an alternative low-band-gap polymer-donor system.},
author = {Dowland, Simon A. and Salvador, Michael Filipe and Perea Ospina, Jose Dario and Gasparini, Nicola and Langner, Stefan and Rajoelson, Sambatra and Ramanitra, Hasina H. and Lindner, Benjamin and Osvet, Andres and Brabec, Christoph and Hiorns, Roger C. and Egelhaaf, Hans-Joachim},
doi = {10.1021/acsami.7b00401},
faupublication = {yes},
journal = {ACS Applied Materials and Interfaces},
keywords = {fullerene aggregation; main-chain polyfullerenes; multi acceptor composite blend; organic photovoltaics; thermal stability},
pages = {10971-10982},
peerreviewed = {unknown},
title = {{Suppression} of {Thermally} {Induced} {Fullerene} {Aggregation} in {Polyfullerene}-{Based} {Multiacceptor} {Organic} {Solar} {Cells}},
volume = {9},
year = {2017}
}
@article{faucris.119640444,
abstract = {The molecular weight of an electron donor-conjugated polymer is as essential as other well-known parameters in the chemical structure of the polymer, such as length and the nature of any side groups (alkyl chains) positioned on the polymeric backbone, as well as their placement, relative strength, the ratio of the donor and acceptor moieties in the backbone of donor-acceptor (D-A)-conjugated polymers, and the arrangement of their energy levels for organic photovoltaic performance. Finding the "optimal" molecular weight for a specific conjugated polymer is an important aspect for the development of novel photovoltaic polymers. Therefore, it is evident that the chemistry of functional conjugated polymers faces major challenges and materials have to adopt a broad range of specifications in order to be established for high photovoltaic performance. In this review, the approaches followed for enhancing the molecular weight of electron-donor polymers are presented in detail, as well as how this influences the optoelectronic properties, charge transport properties, structural conformation, morphology, and the photovoltaic performance of the active layer. Approaches followed for enhancing the molecular weight of the electron donor polymers and how this influences their optoelectronic properties, charge transport properties, structural conformation, morphology, and the photovoltaic performance of the active layer are analyzed and presented in detail.},
author = {Katsouras, Athanasios and Gasparini, Nicola and Koulogiannis, Chrysanthos and Spanos, Michael and Ameri, Tayebeh and Brabec, Christoph and Chochos, Christos L. and Avgeropoulos, Apostolos},
doi = {10.1002/marc.201500398},
faupublication = {yes},
journal = {Macromolecular Rapid Communications},
keywords = {donor-acceptor; molecular weight; organic photovoltaics; polymers},
pages = {1778-1797},
peerreviewed = {unknown},
title = {{Systematic} {Analysis} of {Polymer} {Molecular} {Weight} {Influence} on the {Organic} {Photovoltaic} {Performance}},
volume = {36},
year = {2015}
}
@article{faucris.120868484,
abstract = {Organic bulk heterojunction solar cells based on small molecule acceptors
have recently seen a rapid rise in the power conversion efficiency with values
exceeding 13%. This impressive achievement has been obtained by simultaneous
reduction of voltage and charge recombination losses within this class
of materials as compared to fullerene-based solar cells. In this contribution,
the authors review the current understanding of the relevant photophysical
processes in highly efficient nonfullerene acceptor (NFA) small molecules.
Charge generation, recombination, and charge transport is discussed in
comparison to fullerene-based composites. Finally, the authors review the
superior light and thermal stability of nonfullerene small molecule acceptor
based solar cells, and highlight the importance of NFA-based composites
that enable devices without early performance loss, thus resembling so-called
burn-in free devices.},
author = {Gasparini, Nicola and Wadsworth, Andrew and Moser, Maximilian and Baran, Derya and Mcculloch, Iain and Brabec, Christoph},
doi = {10.1002/aenm.201703298},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {charge recombination, nonfullerene acceptors, organic solar cells, photophysics, stability},
month = {Jan},
peerreviewed = {unknown},
title = {{The} {Physics} of {Small} {Molecule} {Acceptors} for {Efficient} and {Stable} {Bulk} {Heterojunction} {Solar} {Cells}},
year = {2018}
}
@article{faucris.119741204,
abstract = {It is of upmost importance to gain an in-depth understanding of the role of the polymer chemical structure in the performance of the corresponding organic solar cell (OSC) and its degradation behavior, which is currently insufficiently explored. Achieving these correlations will set new design rules towards further optimization of polymer chemical structures for OSCs exhibiting high performances and long stability. In this study, our efforts have been focused on identifying how the nature of aryl substituents and the number of fluorine atoms anchored in the backbone of indacenodithieno[3,2-b]thiophene (IDTT) based polymers influence their optoelectronic properties, the OSC performances and their degradation mechanisms. The most important outcome of this study is the demonstration that standard initial burn-in loss is primary attributed to microstructure instabilities. Furthermore, the initial burn-in loss could be substantially reduced through the rational design of the polymeric semiconductor's chemical structure, leading to improved lifetimes and low (20%) initial power conversion efficiency loss. In particular, we identify the beneficial effect of the presence of the two fluorine atoms on the benzo[c][1,2,5]thiadiazole (BTD), as compared to the non-fluorinated and mono-fluorinated analogues, in decreasing the burn-in by reducing the microstructure instabilities regardless of the aryl substituent that is present in the polymer backbone. © The Royal Society of Chemistry.},
author = {Chochos, Christos L. and Leclerc, Nicolas and Gasparini, Nicola and Zimmerman, Nicolas and Tatsi, Elisavet and Katsouras, Athanasios and Moschovas, Dimitrios and Serpetzoglou, Efthymis and Konidakis, Ioannis and Fall, Sadiara and Leveque, Patrick and Heiser, Thomas and Spanos, Michael and Gregoriou, Vasilis G. and Stratakis, Emmanuel and Ameri, Tayebeh and Brabec, Christoph and Avgeropoulos, Apostolos},
doi = {10.1039/c7ta09224e},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
keywords = {Engineering controlled terms: Chemical stabilityDegradationFluorineImage enhancementMicrostructureOrganic solar cellsPolymer solar cellsPolymersSolar cellsStructure (composition)Substitution reactions Compendex keywords Beneficial effectsBenzothiadiazolesDegradation behaviorDegradation mechanismIn-depth understandingOptoelectronic propertiesPolymeric semiconductorsPower conversion efficiencies Engineering main heading: Structural design},
pages = {25064-25076},
peerreviewed = {unknown},
title = {{The} role of chemical structure in indacenodithienothiophene-alt-benzothiadiazole copolymers for high performance organic solar cells with improved photo-stability through minimization of burn-in loss},
volume = {5},
year = {2017}
}
@article{faucris.123840684,
abstract = {A new ultra low band gap (LBG) α,β-unsubstituted BODIPY-based conjugated polymer has been synthesized by conventional cross coupling polymerization techniques (Stille cross coupling) for the first time. The polymer exhibits a panchromatic absorption spectrum ranging from 300 nm to 1100 nm and an optical band gap (Eoptg) of 1.15 eV, suitable for near infrared (NIR) organic photovoltaic applications as electron donor. Preliminary power conversion efficiency (PCE) of 1.1% in polymer : [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) 1 : 3 weight ratio bulk heterojunction (BHJ) solar cells has been achieved, demonstrating very interesting and promising photovoltaic characteristics, such as good fill factor (FF) and open circuit voltage (Voc). These results showing that by the proper chemical design, new α,β-unsubstituted BODIPY-based NIR copolymers can be developed in the future with suitable energy levels matching those of PC71BM towards more efficient NIR organic photovoltaics (OPVs).},
author = {Squeo, Benedetta M. and Gasparini, Nicola and Ameri, Tayebeh and Palma-Cando, Alex and Allard, Sybille and Gregoriou, Vasilis G. and Brabec, Christoph and Scherf, Ullrich and Chochos, Christos L.},
doi = {10.1039/c5ta04229a},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
pages = {16279-16286},
peerreviewed = {Yes},
title = {{Ultra} low band gap α,β-unsubstituted {BODIPY}-based copolymer synthesized by palladium catalyzed cross-coupling polymerization for near infrared organic photovoltaics},
volume = {3},
year = {2015}
}
@article{faucris.237578399,
abstract = {Elucidating the complex materials distribution in the active layers of ternary organic solar cells is one of the greatest challenges in the field of organic photovoltaics. Knowledge of the nanomorphology is key to understanding photophysical processes (e.g., charge separation, adjustment of the recombination mechanism, and suppression of the radiationless and energetic losses) and thus improving the device performance. Herein, for the first time, the successful discrimination and spatial mapping of the active layer components of a ternary organic solar cell are demonstrated using analytical transmission electron microscopy. The material distribution of all three organic components is successfully visualized by multimodal imaging using complementary electron energy loss signals. A complete picture of the morphological aspects can be gained by studying the lateral and cross-sectional morphology as well as the morphology evolution as a function of the mixing ratio of the polymers. Finally, a correlation between the morphology, photophysical processes, and device performance of the ternary and the reference binary system is achieved, explaining the differences of the power conversion efficiency between the two systems.},
author = {Rechberger, Stefanie and Gasparini, Nicola and Singh, Ranbir and Kim, Min and Chochos, Christos L. and Gregoriou, Vasilis G. and Cho, Kilwon and Brabec, Christoph and Ameri, Tayebeh and Spiecker, Erdmann},
doi = {10.1002/solr.202000114},
faupublication = {yes},
journal = {Solar RRL},
keywords = {device performance; energy-filtered transmission electron microscopy; morphology; ternary organic solar cells; transmission electron microscopy},
note = {CRIS-Team Scopus Importer:2020-04-21},
peerreviewed = {Yes},
title = {{Unraveling} the {Complex} {Nanomorphology} of {Ternary} {Organic} {Solar} {Cells} with {Multimodal} {Analytical} {Transmission} {Electron} {Microscopy}},
year = {2020}
}