Afterglow Effects as a Tool to Screen Emissive Nongeminate Charge Recombination Processes in Organic Photovoltaic Composites.
Keivanidis PE, Itskos G, Kan Z, Aluicio-Sarduy E, Goudarzi H, Kamm V, Laquai F, Zhang W, Brabec C, Floudas G, McCulloch I (2020)
Publication Language: English
Publication Status: Published
Publication Type: Journal article
Publication year: 2020
Journal
Book Volume: 12
Pages Range: 2695-2707
Journal Issue: 2
Abstract
Disentangling temporally overlapping charge carrier recombination events
in organic bulk heterojunctions by optical spectroscopy is challenging. Here, a new
methodology for employing delayed luminescence spectroscopy is presented. The proposed
method is capable of distinguishing between recombination of spatially separated charge
carriers and trap-assisted charge recombination simply by monitoring the delayed
luminescence (afterglow) of bulk heterojunctions with a quasi time-integrated detection
scheme. Applied on the model composite of the donor poly(6,12-dihydro-6,6,12,12-
tetraoctyl-indeno[1,2-b]fluorene-alt-benzothiadiazole) (PIF8BT) polymer and the acceptor ethyl-propyl perylene diimide (PDI) derivative, that is, PIF8BT:PDI, the luminescence of charge-transfer (CT) states created by nongeminate charge recombination on the ns to μs timescale is observed. Fluence-dependent, quasi time-integrated detection of the CT luminescence monitors exclusively emissive charge recombination events, while rejecting the contribution of other early-time emissive processes. Trap-assisted and bimolecular charge recombination channels are identified based on their distinct dependence on fluence. The importance of the two recombination channels is correlated with the layer's order and electrical properties of the corresponding devices. Four different microstructures of the PIF8BT:PDI composite obtained by thermal annealing are investigated. Thermal annealing of PIF8BT:PDI shrinks the PDI domains in parallel with the growth of the PIF8BT domains in the blend. Common to all states studied, the delayed CT luminescence signal is dominated by trap-assisted recombination. Yet, the minor fraction of fully separated charge recombination in the overall CT emission increases as the difference in the size of the donor and acceptor domains in the PIF8BT:PDI blend becomes larger. Electric field-induced quenching measurements on complete PIF8BT:PDI devices confirm quantitatively the dominance of emissive trap-limited charge recombination and demonstrates that only 40% of the PIF8BT/PDI CT luminescence comes from the recombination of fully-separated charges, taking place within 200 ns after photoexcitation. The method is applicable to other nonfullerene acceptor blends beyond the system discussed here, if their CT state luminescence can be monitored.
Authors with CRIS profile
Involved external institutions
King Abdullah University of Science and Technology (KAUST) / جامعة الملك عبد الله للعلوم و التقنية
Saudi Arabia (SA)
Max-Planck-Institut für Polymerforschung (MPI-P) / Max Planck Institute for Polymer Research
Germany (DE)
Italian Institute of Technology / Istituto Italiano di Tecnologia (IIT)
Italy (IT)
University of Cyprus (UCY) / Πανεπιστήμιο Κύπρου
Cyprus (CY)
Cyprus University of Technology (CUT) / Τεχνολογικό Πανεπιστήμιο Κύπρου
Cyprus (CY)
Saudi Arabia (SA)
Max-Planck-Institut für Polymerforschung (MPI-P) / Max Planck Institute for Polymer Research
Germany (DE)
Italian Institute of Technology / Istituto Italiano di Tecnologia (IIT)
Italy (IT)
University of Cyprus (UCY) / Πανεπιστήμιο Κύπρου
Cyprus (CY)
Cyprus University of Technology (CUT) / Τεχνολογικό Πανεπιστήμιο Κύπρου
Cyprus (CY)
How to cite
APA:
Keivanidis, P.E., Itskos, G., Kan, Z., Aluicio-Sarduy, E., Goudarzi, H., Kamm, V.,... McCulloch, I. (2020). Afterglow Effects as a Tool to Screen Emissive Nongeminate Charge Recombination Processes in Organic Photovoltaic Composites. ACS Applied Materials and Interfaces, 12(2), 2695-2707. https://dx.doi.org/10.1021/acsami.9b16036
MLA:
Keivanidis, Panagiotis E., et al. "Afterglow Effects as a Tool to Screen Emissive Nongeminate Charge Recombination Processes in Organic Photovoltaic Composites." ACS Applied Materials and Interfaces 12.2 (2020): 2695-2707.
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