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Title: | On the Interplay between CT and Singlet Exciton Emission in Organic Solar Cells with Small Driving Force and Its Impact on Voltage Loss | Authors: | Fritsch, Tobias Kurpiers, Jona Roland, Steffen Tokmoldin, Nurlan Shoaee, Safa Ferron, Thomas Collins, Brian A. Janietz, Silvia VANDEWAL, Koen Neher, Dieter |
Issue Date: | 2022 | Publisher: | WILEY-V C H VERLAG GMBH | Source: | Advanced Energy Materials, 12 (31) (Art N° 2200641) | Abstract: | The interplay between free charge carriers, charge transfer (CT) states and singlet excitons (S-1) determines the recombination pathway and the resulting open circuit voltage (V-OC) of organic solar cells. By combining a well-aggregated low bandgap polymer with different blend ratios of the fullerenes PCBM and ICBA, the energy of the CT state (E-CT) is varied by 130 meV while leaving the S-1 energy of the polymer (ES1\[{E_{{{\rm{S}}_1}}}\]) unaffected. It is found that the polymer exciton dominates the radiative properties of the blend when ECT\[{E_{{\rm{CT}}}}\] approaches ES1\[{E_{{{\rm{S}}_1}}}\], while the V-OC remains limited by the non-radiative decay of the CT state. It is concluded that an increasing strength of the exciton in the optical spectra of organic solar cells will generally decrease the non-radiative voltage loss because it lowers the radiative V-OC limit (V-OC,V-rad), but not because it is more emissive. The analysis further suggests that electronic coupling between the CT state and the S-1 will not improve the V-OC, but rather reduce the V-OC,V-rad. It is anticipated that only at very low CT state absorption combined with a fairly high CT radiative efficiency the solar cell benefit from the radiative properties of the singlet excitons. | Notes: | Neher, D (corresponding author), Univ Potsdam, Inst Phys & Astron, D-14476 Potsdam, Germany. neher@uni-potsdam.de |
Keywords: | external quantum efficiency;organic photovoltaics;ternary blends;voltage losses | Document URI: | http://hdl.handle.net/1942/37679 | ISSN: | 1614-6832 | e-ISSN: | 1614-6840 | DOI: | 10.1002/aenm.202200641 | ISI #: | WOS:000817784600001 | Rights: | 2022 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. | Category: | A1 | Type: | Journal Contribution | Validations: | ecoom 2023 |
Appears in Collections: | Research publications |
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