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@article{faucris.108247964,
abstract = {The performance of organic solar cells is determined by the delicate, meticulously optimized bulk-heterojunction microstructure, which consists of finely mixed and relatively separated donor/acceptor regions. Here we demonstrate an abnormal strong burn-in degradation in highly efficient polymer solar cells caused by spinodal demixing of the donor and acceptor phases, which dramatically reduces charge generation and can be attributed to the inherently low miscibility of both materials. Even though the microstructure can be kinetically tuned for achieving high-performance, the inherently low miscibility of donor and acceptor leads to spontaneous phase separation in the solid state, even at room temperature and in the dark. A theoretical calculation of the molecular parameters and construction of the spinodal phase diagrams highlight molecular incompatibilities between the donor and acceptor as a dominant mechanism for burn-in degradation, which is to date the major short-time loss reducing the performance and stability of organic solar cells.},
author = {Li, Ning and Perea, José Darío and Kassar, Thaer and Richter, Moses and Heumüller, Thomas and Matt, Gebhard and Hou, Yi and Güldal, Nusret Sena and Chen, Haiwei and Chen, Shi and Langner, Stefan and Berlinghof, Marvin and Unruh, Tobias and Brabec, Christoph},
doi = {10.1038/ncomms14541},
faupublication = {yes},
journal = {Nature Communications},
peerreviewed = {Yes},
title = {{Abnormal} strong burn-in degradation of highly efficient polymer solar cells caused by spinodal donor-acceptor demixing},
volume = {8},
year = {2017}
}
@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.119560584,
abstract = {A major bottleneck delaying the further commercialization of thin-film solar cells based on hybrid organohalide lead perovskites is the interface losses in state-of-the-art devices. We present a generic interface architecture that combines solution-processed, reliable, and cost-efficient hole-transporting materials, without compromising efficiency, stability or scalability of perovskite solar cells. Tantalum doped tungsten oxide (Ta-WOx)/conjugated polymer multilayers offer a surprisingly small interface barrier and form quasi-ohmic contacts universally with various scalable conjugated polymers. Using a simple regular planar architecture device, Ta-WOx doped interface-based perovskite solar cells achieve maximum efficiencies of 21.2% and combined with over 1000 hours of light stability based on a self-assembled monolayer. By eliminating additional ionic dopants, these findings open up the whole class of organics as scalable hole-transporting materials for perovskite solar cell},
author = {Hou, Yi and Du, Xiaoyan and Scheiner, Simon and McMeekin, David P. and Wang, Zhiping and Li, Ning and Killian, Manuela and Chen, Haiwei and Richter, Moses and Levchuk, Ievgen and Schrenker, Nadine and Spiecker, Erdmann and Stubhan, Tobias and Luechinger, Norman A. and Hirsch, Andreas and Schmuki, Patrik and Steinrück, Hans-Peter and Fink, Rainer and Halik, Marcus and Snaith, Henry J. and Brabec, Christoph},
doi = {10.1126/science.aao5561},
faupublication = {yes},
journal = {Science},
pages = {1-9},
peerreviewed = {Yes},
title = {{A} generic interface to reduce the efficiency-stability-cost gap of perovskite solar cells},
year = {2017}
}
@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.210192939,
abstract = {Mesoscale-structured materials offer broad opportunities in extremely diverse
applications owing to their high surface areas, tunable surface energy, and
large pore volume. These benefits may improve the performance of materials
in terms of carrier density, charge transport, and stability. Although metal
oxides–based mesoscale-structured materials, such as TiO2, predominantly
hold the record efficiency in perovskite solar cells, high temperatures (above
400 °C) and limited materials choices still challenge the community. A novel
route to fabricate organic-based mesoscale-structured interfaces (OMI) for
perovskite solar cells using a low-temperature and green solvent–based process
is presented here. The efficient infiltration of organic porous structures
based on crystalline nanoparticles allows engineering efficient “n-i-p” and
“p-i-n” perovskite solar cells with enhanced thermal stability, good performance,
and excellent lateral homogeneity. The results show that this method
is universal for multiple organic electronic materials, which opens the door to
transform a wide variety of organic-based semiconductors into scalable n- or
p-type porous interfaces for diverse advanced applications.
solar cells. In this manuscript we reveal a several Å thick Methylammonium Iodide (MAI) rich
interface between the perovskite and the metal oxide. Surface functionalization via selfassembled
monolayers (SAMs) allowed us to control the composition of the interface
monolayer from Pb poor to Pb rich, which in parallel suppresses hysteresis in perovskite
solar cells. The bulk of the perovskite films is not affected by the interface engineering and
remains highly crystalline in surface normal direction over the whole film thickness. The subnm
structural modifications of the buried interface were revealed by x-ray reflectivity (XRR),
which is most sensitive to monitor changes in the mass density of only several Å thin
interfacial layers as a function of substrate functionalization. From Kelvin probe force
microscopy (KPFM) on a solar cell cross section study, we further demonstrate local
variations of the potential on different electron transporting layers (ETLs) within a solar cell.
Based on these findings we present a unifying model explaining hysteresis in perovskite solar
cells, giving for the first time insight into one crucial aspect of hysteresis and paving the way
for new strategies in the fields of perovskite based opto-electronic devices.},
author = {Will, Johannes and Hou, Yi and Scheiner, Simon and Pinkert, Ute and Hermes, Ilka M. and Weber, Stefan A.L. and Hirsch, Andreas and Halik, Marcus and Brabec, Christoph and Unruh, Tobias},
doi = {10.1021/acsami.7b15904},
faupublication = {yes},
journal = {ACS Applied Materials and Interfaces},
keywords = {perovskite solar cell, hysteresis, buried interface, x-ray reflectivity, Kelvin probe force microscopy},
month = {Jan},
pages = {5511-5518},
peerreviewed = {Yes},
title = {{Evidence} of {Tailoring} the {Interfacial} {Chemical} {Composition} in {Normal} {Structure} {Hybrid} {Organohalide} {Perovskites} by a {Self}-{Assembled} {Monolayer}},
url = {https://pubs.acs.org/doi/abs/10.1021/acsami.7b15904},
volume = {10},
year = {2018}
}
@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.119390524,
abstract = {Currently, lead-based perovskites with mixed multiple cations and hybrid
halides are attracting intense research interests due to their promising
stability and high efficiency. A tremendous amount of 3D and 2D perovskite
compositions and configurations are causing a strong demand for high
throughput synthesis and characterization. Furthermore, wide bandgap
(≈1.75 eV) perovskites as promising top-cell materials for perovskite–silicon
tandem configurations require the screening of different compositions to
overcome photoinduced halide segregation and still yielding a high opencircuit
voltage (Voc). Herein, a home-made high throughput robot setup is
introduced performing automatic perovskite synthesis and characterization.
Subsequently, four kinds of compositions (i.e., cation mixtures of Cs–methylammonium
(MA), Cs– formamidinium (FA), MA–FA, and FA–MA) with an
optical bandgap of ≈1.75 eV are identified as promising device candidates.
For Cs–MA and Cs–FA films it is found that the Br–I phase segregation
indeed can be overcome. Moreover, Cs–MA, MA–FA, and Cs–FA based
devices exhibit an average Voc of 1.17, 1.17, 1.12 V, and their maximum values
approached 1.18, 1.19, 1.14 V, respectively, which are among the highest Voc
(≈1.2 V) values for ≈40% Br perovskite. These findings highlight that the high
throughput approach can effectively and efficiently accelerate the invention of
novel perovskites for advanced applications.},
author = {Chen, Shi and Hou, Yi and Chen, Haiwei and Tang, Xiaofeng and Langner, Stefan and Li, Ning and Stubhan, Tobias and Levchuk, Ievgen and Gu, Ening and Osvet, Andres and Brabec, Christoph},
doi = {10.1002/aenm.201701543},
faupublication = {yes},
journal = {Advanced Energy Materials},
peerreviewed = {unknown},
title = {{Exploring} the {Stability} of {Novel} {Wide} {Bandgap} {Perovskites} by a {Robot} {Based} {High} {Throughput} {Approach}},
url = {http://onlinelibrary.wiley.com/doi/10.1002/aenm.201701543/abstract},
year = {2017}
}
@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.123759504,
abstract = {In this work, we report efficient semitransparent perovskite solar cells using solution-processed silver nanowires (AgNWs) as top electrodes. A thin layer of zinc oxide nanoparticles is introduced beneath the AgNWs, which fulfills two essential functionalities: it ensures ohmic contact between the PC60BM and the AgNWs and it serves as a physical foundation that enables the solution-deposition of AgNWs without causing damage to the underlying perovskite. The as-fabricated semitransparent perovskite cells show a high fill factor of 66.8%, V-oc = 0.964 V, J(sc) = 13.18 mA cm(-2), yielding an overall efficiency of 8.49% which corresponds to 80% of the reference devices with reflective opaque electrode},
author = {Guo, Fei and Azimi, Seyed Hamed and Hou, Yi and Przybilla, Thomas and Hu, Mengyao and Bronnbauer, Carina and Langner, Stefan and Spiecker, Erdmann and Forberich, Karen and Brabec, Christoph},
doi = {10.1039/c4nr06033d},
faupublication = {yes},
journal = {Nanoscale},
month = {Jan},
pages = {1642-1649},
peerreviewed = {Yes},
title = {{High}-performance semitransparent perovskite solar cells with solution-processed silver nanowires as top electrodes},
volume = {7},
year = {2015}
}
@article{faucris.122399244,
abstract = {No abstract available for this article},
author = {Zhang, Hong and Azimi, Seyed Hamed and Hou, Yi and Ameri, Tayebeh and Przybilla, Thomas and Spiecker, Erdmann and Kraft, Mario and Scherf, Ullrich and Brabec, Christoph},
doi = {10.1021/cm502864s},
faupublication = {yes},
journal = {Chemistry of Materials},
pages = {5190--5193},
peerreviewed = {Yes},
title = {{Improved} {High}-{Efficiency} {Perovskite} {Planar} {Heterojunction} {Solar} {Cells} via {Incorporation} of a {Polyelectrolyte} {Interlayer}},
volume = {26},
year = {2014}
}
@article{faucris.106817524,
abstract = {Kesterite CuZnSnS(CZTS) is a promising material for thin film solar cell applications. The biggest advantages of this compound lie in the abundance and non-toxicity of the contained elements. Low temperature hot injection synthesis can provide an economic way to produce CZTS nanoparticles for application in solution processed solar cells. Powder X-ray diffraction (PXRD) measurements on the as-synthesised particles suggest that the crystal structure is cubic and can be best described as sphalerite-like. This means that the cations in the CZTS are statistically distributed on the cation sites of the crystal lattice rather than well-ordered like in the tetragonal kesterite structure. An in-situ PXRD measurement while annealing the particles up to 550 °C revealed a recrystallization process that transforms the structure from cubic to tetragonal meaning an ordering of the cations.},
author = {Brandl, Marco and Ahmad, Rameez and Distaso, Monica and Azimi, Seyed Hamed and Hou, Yi and Peukert, Wolfgang and Brabec, Christoph and Hock, Rainer},
doi = {10.1016/j.tsf.2014.10.077},
faupublication = {yes},
journal = {Thin Solid Films},
keywords = {Copper zinc tin sulphide; Cubic phase; Hot-injection synthesis; In-situ; Phase transition; Tetragonal phase; X-ray diffraction},
pages = {269-271},
peerreviewed = {Yes},
title = {{In}-situ {X}-ray diffraction analysis of the recrystallization process in {Cu2ZnSnS4nanoparticles} synthesised by hot-injection},
volume = {582},
year = {2015}
}
@article{faucris.213328320,
abstract = {Kesterite Cu2ZnSnS4 (CZTS) is a promisingmaterial for thin film solar cell applications. The biggest advantages of this compound lie in the abundance and non-toxicity of the contained elements. Low temperature hot injection synthesis can provide an economic way to produce CZTS nanoparticles for application in solution processed solar cells. Powder X-ray diffraction (PXRD) measurements on the as-synthesised particles suggest that the crystal structure is cubic and can be best described as sphalerite-like. This means that the cations in the CZTS are statistically distributed on the cation sites of the crystal lattice rather than well-ordered like in the tetragonal kesterite structure. An in-situ PXRD measurement while annealing the particles up to 550 °C revealed a recrystallization process that transforms the structure from cubic to tetragonal meaning an ordering of the cations.},
author = {Brandl, Marco and Ahmad, Rameez and Distaso, Monica and Azimi, Hamed and Hou, Yi and Peukert, Wolfgang and Brabec, Christoph and Hock, Rainer},
doi = {10.1016/j.tsf.2014.10.077},
faupublication = {yes},
journal = {Thin Solid Films},
note = {EAM Import::2019-03-13},
pages = {269-271},
peerreviewed = {Yes},
title = {{In}-{Situ} {X}-ray {Diffraction} {Analysis} of the {Recrystallization} {Process} in {Cu2ZnSnS4} {Nano} {Particles} {Synthesized} by {Hot}-{Injection}},
volume = {582},
year = {2015}
}
@article{faucris.118496664,
abstract = {Perovskite hybrid solar cells (pero-HSCs) were demonstrated to be among the most promising candidates within the emerging photovoltaic materials with respect to their power conversion efficiency (PCE) and inexpensive fabrication. Further PCE enhancement mainly relies on minimizing the interface losses via interface engineering and the quality of the perovskite film. Here, we demonstrate that the PCEs of pero-HSCs are significantly increased to 14.0\% by incorporation of a solution-processed perylene–diimide (PDINO) as cathode interface layer between the [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) layer and the top Ag electrode. Notably, for PDINO-based devices, prominent PCEs over 13\% are achieved within a wide range of the PDINO thicknesses (5–24 nm). Without the PDINO layer, the best PCE of the reference PCBM/Ag device was only 10.0\%. The PCBM/PDINO/Ag devices also outperformed the PCBM/ZnO/Ag devices (11.3\%) with the well-established zinc oxide (ZnO) cathode interface layer. This enhanced performance is due to the formation of a highly qualitative contact between PDINO and the top Ag electrode, leading to reduced series resistance (Rs) and enhanced shunt resistance (Rsh) values. This study opens the door for the integration of a new class of easily-accessible, solution-processed high-performance interfacial materials for pero-HSCs.},
author = {Min, Jie and Zhang, Zhi-Guo and Hou, Yi and Ramírez Quiroz, César Omar and Przybilla, Thomas and Bronnbauer, Carina and Guo, Fei and Forberich, Karen and Azimi, Seyed Hamed and Ameri, Tayebeh and Spiecker, Erdmann and Li, Yongfang and Brabec, Christoph},
doi = {10.1021/cm5037919},
faupublication = {yes},
journal = {Chemistry of Materials},
pages = {227--234},
peerreviewed = {Yes},
title = {{Interface} {Engineering} of {Perovskite} {Hybrid} {Solar} {Cells} with {Solution}-{Processed} {Perylene}–{Diimide} {Heterojunctions} toward {High} {Performance}},
volume = {27},
year = {2015}
}
@article{faucris.120979804,
abstract = {A power conversion efficiency of 11.8% is demonstrated for planar perovskite solar cell based on acid water-free poly(3,4-ethylenedioxythiophene) (PEDOT) as the hole-transporting layer. This efficiency is further improved to 14.2% using a pH neutralized PEDOT, which reduces the sub-gap defects at the surface of perovskite. All the active layers reported are solution-processed at temperatures below 140 °C making it compatible with roll-to-roll production.},
author = {Hou, Yi and Zhang, Hong and Chen, Wei and Chen, Shi and Ramírez Quiroz, César Omar and Azimi, Seyed Hamed and Osvet, Andres and Matt, Gebhard and Zeira, Eitan and Seuring, Jan and Kausch-Busies, Nina and Loevenich, Wilfried and Brabec, Christoph},
doi = {10.1002/aenm.201500543},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {low-temperature processing; perovskite solar cells; stabilities; water-free poly(3,4-ethylenedioxythiophene)},
peerreviewed = {unknown},
title = {{Inverted}, {Environmentally} {Stable} {Perovskite} {Solar} {Cell} with a {Novel} {Low}-{Cost} and {Water}-{Free} {PEDOT} {Hole}-{Extraction} {Layer}},
volume = {5},
year = {2015}
}
@article{faucris.215222860,
abstract = {Drift-diffusion modeling of the ionic dipole switching from the measurement of fast scanned and long pre-biased electrical response is proposed as a novel protocol for evaluation of limit hysteretic effects in perovskite solar cells. Up to eight systems were measured including CH3NH3PbI3, Cs0.1FA0.74MA0.13PbI2.48Br0.39 and FA0.83MA0.17Pb1.1Br0.22I2.98 3D perovskite absorbers, as well as 2D capping layers towards the selective contacts. We show systematic hysteretic patterns, even among typical hysteresis-free devices, including normal and inverted hysteresis as general dissimilar trend between CH3NH3PbI3 and mixed perovskite cells, respectively. Particularly, strong changes in the short-circuit current density (Jsc) were identified, in addition to different trends affecting the fill factor (FF) and the open-circuit voltage (Voc). The changes in Jsc were analyzed with state-of-the-art numerical drift-diffusion simulations concluding in an important reduction in the charge collection due to ionic distribution switching depending on the pre-biasing protocol and the type of absorbing perovskite. It is shown that mixed perovskites inhibit ionic dipolar switching. In addition, our calculi signal on the required conditions for the occurrence of inverted hysteresis and changes in the Voc. Regarding the FF and Voc patterns a new empirical approach is introduced and corresponding interpretations are proposed.
2ZnSn(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.123734864,
abstract = {It is shown that the performance of inverted organic solar cells can be significantly improved by facilitating the formation of a quasi-ohmic contact via solution-processed alkali hydroxide (AOH) interlayers on top of n-type metal oxide (aluminum zinc oxide, AZO, and zinc oxide, ZnO) layers. AOHs significantly reduce the work function of metal oxides, and are further proven to effectively passivate defect states in these metal oxides. The interfacial energetics of these electron collecting contacts with a prototypical electron acceptor (C) are investigated to reveal the presence of a large interface dipole and a new interface state between the Fermi energy and the C highest occupied molecular orbital for AOH-modified AZO contacts. These novel interfacial gap states are a result of ground-state electron transfer from the metal hydroxide-functionalized AZO contact to the adsorbed molecules, which are hypothesized to be electronically hybridized with the contact. These interface states tail all the way to the Fermi energy, providing for a highly n-doped (metal-like) interfacial molecular layer. Furthermore, the strong "light-soaking" effect is no longer observed in devices with a AOH interface. Solution-processed alkali hydroxides significantly reduce the work function of metal oxides, such as zinc oxide or aluminum zinc oxide (AZO), and are further proven to effectively passivate defect states in these metal oxides. The interface states with alkali hydroxide-modified AZO contacts tail all the way to the Fermi energy, providing for a highly n-doped (metal-like) interfacial molecular layer.},
author = {Zhang, Hong and Shallcross, R. Clayton and Li, Ning and Stubhan, Tobias and Hou, Yi and Chen, Wei and Ameri, Tayebeh and Turbiez, Mathieu and Armstrong, Neal R. and Brabec, Christoph},
doi = {10.1002/aenm.201502195},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {alkali hydroxide; interfacial layers; organic solar cells; solution processing},
peerreviewed = {unknown},
title = {{Overcoming} {Electrode}-{Induced} {Losses} in {Organic} {Solar} {Cells} by {Tailoring} a {Quasi}-{Ohmic} {Contact} to {Fullerenes} via {Solution}-{Processed} {Alkali} {Hydroxide} {Layers}},
volume = {6},
year = {2016}
}
@article{faucris.106802784,
abstract = {An experiment was conducted to demonstrate that low-temperature processed NiO-based nanocrystal ink (LT-NiO) has the potential to form an almost loss-free hole selective interface for flat heterojunction perovskite-based solar cells. First, The patterned ITO substrates were ultrasonic cleaned with acetone and isopropanol for 10 min each. On cleaned ITO substrate, a dense and smooth layer of LT-NiO was deposited by spin coating and followed by annealing at 70?230°C for 10 min in air to remove organic components. The as-prepared perovskite precursor solution was filtered using 0.45 μm PTFE syringe filter and coated onto the ITO/LT-NiO substrate at a speed of 4000 r.p.m. for 35 s. J-V characteristics of all the devices were measured using a source measurement unit from BoTest. FTPS:FTPS-EQE measurements were carried out using a Vertex 70 from Brucker optics, equipped with QTH lamp, quartz beam splitter and external detector option. A major improvement in open circuit voltage is found by replacing PEDOT:PSS with LT-NiO. A detailed analysis reveals that LT-NiO significantly reduces non-radiative recombination at the PEDOT:PSS/perovskite interface and further enhances the radiative LED efficiency towards unity which brings open circuit voltage closer to the radiative limit.},
author = {Hou, Yi and Chen, Wei and Baran, Derya and Stubhan, Tobias and Luechinger, Norman A. and Hartmeier, Benjamin and Richter, Moses and Min, Jie and Chen, Shi and Ramírez Quiroz, César Omar and Li, Ning and Zhang, Hong and Heumüller, Thomas and Matt, Gebhard and Osvet, Andres and Forberich, Karen and Zhang, Zhi-Guo and Li, Yongfang and Winter, Benjamin and Schweizer, Peter and Spiecker, Erdmann and Brabec, Christoph},
doi = {10.1002/adma.201504168},
faupublication = {yes},
journal = {Advanced Materials},
keywords = {low temperature processing; nickel oxide; non-radiative voltage loss; perovskite solar cells},
pages = {5112-5120},
peerreviewed = {unknown},
title = {{Overcoming} the {Interface} {Losses} in {Planar} {Heterojunction} {Perovskite}-{Based} {Solar} {Cells}},
year = {2016}
}
@article{faucris.123736844,
abstract = {Photoinduced degradation is a critical obstacle for the real application of novel semiconductors for photovoltaic applications. In this paper, the photoinduced degradation of CHNHPbI in a vacuum and air (relative humidity 40%) is analyzed by ex situ and advanced in situ technologies. Without light illumination, CHNHPbI films slowly degrade under vacuum and air within 24 hours. However, we find that CHNHPbI converts to metallic lead (Pb) when exposed to vacuum and light illumination. Further, a series of lead salts (e.g. PbO, Pb(OH) and PbCO) are formed when CHNHPbI is degraded under environmental conditions, i.e. under the combination of light, oxygen and moisture. Photoinduced degradation is found to be determined by the environmental atmosphere as CHNHPbI films remain very stable under nitrogen conditions. The results from vacuum conditions underpin that the high volatility of the organic component (CHNHI) is in conflict with reaching excellent intrinsic stability due to its role in creating ion vacancies. The degradation in air suggests that both oxygen and water contribute to the fast photodecomposition of CHNHPbI into lead salts rather than water alone. Given these basic yet fundamental understandings, the design of hydrophobic capping layers becomes one prerequisite towards long-term stable perovskite-based devices.},
author = {Tang, Xiaofeng and Brandl, Marco and May, Benjamin and Levchuk, Ievgen and Hou, Yi and Richter, Moses and Chen, Haiwei and Chen, Shi and Kahmann, Simon and Osvet, Andres and Maier, Florian and Steinrück, Hans-Peter and Hock, Rainer and Matt, Gebhard and Brabec, Christoph},
doi = {10.1039/c6ta06497c},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
keywords = {Engineering controlled terms: Lead; Perovskite; Salts; Slow light Environmental conditions; Intrinsic stability; Light illumination; Organic components; Photo-decomposition; Photoinduced degradation; Photovoltaic applications; Real applications Engineering main heading: Photodegradation},
pages = {15896-15903},
peerreviewed = {unknown},
title = {{Photoinduced} degradation of methylammonium lead triiodide perovskite semiconductors},
volume = {4},
year = {2016}
}
@article{faucris.115829384,
abstract = {While perovskite-based semitransparent solar cells deliver competitive levels of transparency and efficiency to be envisioned for urban infrastructures, the complexity and sensitivity of their processing conditions remain challenging. Here, we introduce two robust protocols for the processing of sub-100 nm perovskite films, allowing fine-tuning of the active layer without compromising the crystallinity and quality of the semiconductor. Specifically, we demonstrate that a method based on solvent-induced crystallization with a rapid drying step affords perovskite solar cells with 37% average visible transmittance (AVT) and 7.8% PCE. This process enhances crystallization with a preferential phase orientation presumably at the interface, yielding a high fill factor of 72.3%. The second method is based on a solvent-solvent extraction protocol, enabling active layer films as thin as 40 nm and featuring room-temperature crystallization in an ambient environment on a few second time span. As a result, we demonstrate a maximum AVT of 46% with an efficiency of 3.6%, which is the highest combination of efficiency and transparency for a full device stack to date. By combining the two methods presented here we cover a broad range of thicknesses vs. transparency values and confirm that solvent-induced crystallization represents a powerful processing strategy toward high-efficiency semitransparent solar cells. Optical simulations support our experimental findings and provide a global perspective of the opportunities and limitations of semitransparent perovskite photovoltaic devices.},
author = {Ramírez Quiroz, César Omar and Levchuk, Ievgen and Bronnbauer, Carina and Salvador, Michael Filipe and Forberich, Karen and Heumüller, Thomas and Hou, Yi and Schweizer, Peter and Spiecker, Erdmann and Brabec, Christoph},
doi = {10.1039/c5ta08450d},
faupublication = {yes},
journal = {Journal of Materials Chemistry A},
pages = {24071-24081},
peerreviewed = {Yes},
title = {{Pushing} efficiency limits for semitransparent perovskite solar cells},
volume = {3},
year = {2015}
}
@article{faucris.204906461,
abstract = {Thin-film solar cells based on hybrid organo-halide lead perovskites achieve
over 22% power conversion efficiency (PCE). A photovoltaic technology at
such high performance is no longer limited by efficiency. Instead, lifetime and
reliability become the decisive criteria for commercialization. This requires a
standardized and scalable architecture which does fulfill all requirements for
larger area solution processing. One of the most highly demanded technologies
is a low temperature and printable conductive ink to substitute evaporated
metal electrodes for the top contact. Importantly, that electrode technology
must have higher environmental stability than, for instance, an evaporated
silver (Ag) electrode. Herein, planar and entirely low-temperature-processed
perovskite devices with a printed carbon top electrode are demonstrated. The
carbon electrode shows superior photostability compared to reference devices
with an evaporated Ag top electrode. As hole transport material, poly (3′hexyl
thiophene) (P3HT) and copper(I) thiocyanate (CuSCN), two cost-effective
and commercially available p-type semiconductors are identified to effectively
replace the costlier 2,2′,7,7′-Tetrakis-(N,N-di-4-methoxyphenylamino)-
9,9′-spirobifluorene (spiro-MeOTAD). While methylammonium lead iodide
(MAPbI3)-based perovskite solar cells (PSCs) with an evaporated Ag electrode
degrade within 100 h under simulated sunlight (AM 1.5), fully solution-processed
PSCs with printed carbon electrodes preserve more than 80% of their
initial PCE after 1000 h of constant illumination.
3 on freshly cleaved NaCl single-crystal substrates. Only two of the four main types of CsPbBr3 crystallization observed are epitaxial. The microscopic observation of composition gradients at the interface of CsPbBr3 grains and substrates reveals a promising opportunity to manipulate the lattice constant at the interface by simply controlling the temperature and concentration.},
author = {Elia, Jack and Levchuk, Ievgen and Hou, Yi and Matt, Gebhard and These, Albert and Zhao, Yicheng and Zhang, Jiyun and Forberich, Karen and Osvet, Andres and Götz, Klaus and Prihoda, Annemarie and Wu, Mingjian and Harreiß, Christina and Rechberger, Stefanie and Will, Johannes and Unruh, Tobias and Spiecker, Erdmann and Zorenko, Yuriy and Batentschuk, Miroslaw and Brabec, Christoph},
doi = {10.1021/acs.jpcc.3c06162},
faupublication = {yes},
journal = {Journal of Physical Chemistry C},
note = {CRIS-Team Scopus Importer:2023-12-08},
peerreviewed = {Yes},
title = {{Solution}-{Growth} {Liquid}-{Phase} {Epitaxy} of {CsPbBr3} on {NaCl} by {Optimizing} the {Substrate} {Dissolution}},
year = {2023}
}
@article{faucris.246729220,
abstract = {Light-induced halide segregation limits the bandgap tunability of mixed-halide perovskites for tandem photovoltaics. Here we report that light-induced halide segregation is strain-activated in MAPb(I1−xBrx)3 with Br concentration below approximately 50%, while it is intrinsic for Br concentration over approximately 50%. Free-standing single crystals of CH3NH3Pb(I0.65Br0.35)3 (35%Br) do not show halide segregation until uniaxial pressure is applied. Besides, 35%Br single crystals grown on lattice-mismatched substrates (e.g. single-crystal CaF2) show inhomogeneous segregation due to heterogenous strain distribution. Through scanning probe microscopy, the above findings are successfully translated to polycrystalline thin films. For 35%Br thin films, halide segregation selectively occurs at grain boundaries due to localized strain at the boundaries; yet for 65%Br films, halide segregation occurs in the whole layer. We close by demonstrating that only the strain-activated halide segregation (35%Br/45%Br thin films) could be suppressed if the strain is properly released via additives (e.g. KI) or ideal substrates (e.g. SiO2).
2-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.201281604,
abstract = {Lead halide perovskites often suffer from a strong hysteretic behavior on their j–V response in photovoltaic devices that has been correlated with slow ion migration.
The electron extraction layer has frequently been pointed to as the main culprit for
the observed hysteretic behavior. In this work three hole transport layers are studied
with well‐defined highest occupied molecular orbital (HOMO) levels and interestingly
the hysteretic behavior is markedly different. Here it is shown that an adequate energy
level alignment between the HOMO level of the extraction layer and the valence band
of the perovskite, not only suppresses the hysteresis, avoiding charge accumulation
at the interfaces, but also degradation of the hole transport layer is reduced. Numerical
simulation suggests that formation of an injection barrier at the organic/perovskite
heterointerface could be one mechanism causing hysteresis. The suppression of such
barriers may require novel design rules for interface materials. Overall, this work
highlights that both external contacts need to be carefully optimized in order to
obtain hysteresis‐free perovskite devices.},
author = {Guerrero, Antonio and Bou, Agustín and Matt, Gebhard and Almora, Osbel and Heumüller, Thomas and Garcia-Belmonte, Germà and Bisquert, Juan and Hou, Yi and Brabec, Christoph},
doi = {10.1002/aenm.201703376},
faupublication = {yes},
journal = {Advanced Energy Materials},
keywords = {Charge accumulation; Hysteresis; Perovskites; Energy barrier; Hole extraction layer},
peerreviewed = {unknown},
title = {{Switching} {Off} {Hysteresis} in {Perovskite} {Solar} {Cells} by {Fine}-{Tuning} {Energy} {Levels} of {Extraction} {Layers}},
url = {https://onlinelibrary.wiley.com/doi/abs/10.1002/aenm.201703376},
volume = {8},
year = {2018}
}
@article{faucris.205647528,
abstract = {Charge selective contact layers in perovskite solar cells influence the current density-voltage
hysteresis, an effect related to ion migration in the perovskite. As such, fullerene-based electron
transport layers (ETL) suppress hysteresis by reducing the mobile ion concentration. However, the
impact of different ETL on the electronic properties of other constituent device layers remains
unclear. In this Kelvin probe force microscopy study, we compared potential distributions of
methylammonium lead iodide-based solar cells with two ETL (planar TiO2 and C60-functionalized
self-assembled monolayer) with different hysteretic behavior. We found significant changes in the
potential distribution of the organic hole transport layer spiroMeOTAD, suggesting the formation
of a neutral spiroMeOTAD-iodide interface due to a reaction between iodide with p-doped
spiroMeOTAD in the TiO2 cell. Our results show that the ETL affects not only the mobile ion concentration and the recombination at the perovskite/ETL interface but also the resistance and capacitance of the spiroMeOTAD.},
author = {Hermes, Ilka M. and Hou, Yi and Bergmann, Victor W. and Brabec, Christoph and Weber, Stefan A.L.},
doi = {10.1021/acs.jpclett.8b02824},
faupublication = {yes},
journal = {Journal of Physical Chemistry Letters},
pages = {6249-6256},
peerreviewed = {Yes},
title = {{The} {Interplay} of {Contact} {Layers}: {How} the {Electron} {Transport} {Layer} {Influences} {Interfacial} {Recombination} and {Hole} {Extraction} in {Perovskite} {Solar} {Cells}.},
year = {2018}
}
@article{faucris.124033404,
abstract = {Solution-processed organic and inorganic semiconductors offer a promising path towards low-cost mass production of solar cells. Among the various material systems, solution processing of multicomponent inorganic semiconductors offers considerable promise due to their excellent electronic properties and superior photo- and thermal stability. This review surveys the recent developments of "all solution-processed" copper-indium (-gallium)-chalcogenide (CuInS, CuInSe and Cu(In, Ga)(Se, S)) chalcopyrites and copper-zinc-tin-chalcogenide (CuZnSnS and CuZnSnSe (CZTS(e))) kesterite solar cells. A brief overview further addresses some of the most critical material aspects and associated loss mechanisms in chalcopyrite and kesterite devices. Today's state-of-the-art performance as well as future challenges to achieve low-cost and environmentally friendly production is discussed. This journal is © the Partner Organisations 2014.},
author = {Azimi, Seyed Hamed and Hou, Yi and Brabec, Christoph},
doi = {10.1039/c3ee43865a},
faupublication = {yes},
journal = {Energy and Environmental Science},
keywords = {Engineering controlled terms: Chalcogenides; Copper compounds; Costs; Electronic properties; Gallium Cu(In ,Ga)(Se ,S)2; Future challenges; Inorganic semiconductors; Mass production; Material systems; Solution-processed; Solution-processing; State-of-the-art performance Engineering main heading: Solar cells GEOBASE Subject Index: alternative energy; cost analysis; fuel cell; renewable resource; solar power},
pages = {1829-1849},
peerreviewed = {unknown},
title = {{Towards} low-cost, environmentally friendly printed chalcopyrite and kesterite solar cells},
volume = {7},
year = {2014}
}
@article{faucris.232032039,
abstract = {Cesium lead iodide (CsPbI3) has attracted increasing attention for its photovoltaic applications, owing to its thermal stability and suitable band gap for tandem solar cells. However, the severe nonradiative recombination losses in CsPbI3-based perovskite solar cells generally restrict their open-circuit voltage (VOC) to the range of 0.9 to 1.1 V. This work uniquely reports a method to visualize all defect-assisted recombination pathways with photoluminescence (PL) techniques. Visible and valuable insight into the reduction of defect densities on a micrometer scale was obtained by the bottom surface and bulk passivation with barium hydroxide and trioctylphosphine oxide. The dual effects successfully improve the VOC of the solar cell from 0.87 to 1.17 V. These results highlight the potential of hyperspectral PL imaging as a powerful tool to give guidance to further suppress the nonradiative VOC losses in all-inorganic perovskites.},
author = {Meng, Wei and Hou, Yi and Karl, André and Gu, Ening and Tang, Xiaofeng and Osvet, Andres and Zhang, Kaicheng and Zhao, Yicheng and Du, Xiaoyan and García Cerrillo, José and Li, Ning and Brabec, Christoph},
doi = {10.1021/acsenergylett.9b02604},
faupublication = {yes},
journal = {ACS Energy Letters},
note = {CRIS-Team Scopus Importer:2020-01-21},
pages = {271-279},
peerreviewed = {Yes},
title = {{Visualizing} and {Suppressing} {Nonradiative} {Losses} in {High} {Open}-{Circuit} {Voltage} n-i-p-{Type} {CsPbI3} {Perovskite} {Solar} {Cells}},
year = {2020}
}