The role of delocalization and excess energy in the quantum efficiency of organic solar cells and the validity of optical reciprocity relations
The photon energy dependence of long-range charge separation is studied for two prototypical polymer:fullerene systems. The internal quantum efficiency (IQE) of PCDTBT:PC61BM is experimentally shown to be independent of the excitation energy. In contrast, for TQ1:PC71BM the IQE is strongly energy-de...
Saved in:
| Main Authors: | , , |
|---|---|
| Format: | Article (Journal) |
| Language: | English |
| Published: |
April 17, 2020
|
| In: |
The journal of physical chemistry letters
Year: 2020, Volume: 11, Issue: 9, Pages: 3563-3570 |
| ISSN: | 1948-7185 |
| DOI: | 10.1021/acs.jpclett.0c00945 |
| Online Access: | Verlag, lizenzpflichtig, Volltext: https://dx.doi.org/10.1021/acs.jpclett.0c00945 Verlag, lizenzpflichtig, Volltext: https://doi.org/10.1021/acs.jpclett.0c00945 
|
| Author Notes: | N. Felekidis, A. Melianas, and M. Kemerink |
| Summary: | The photon energy dependence of long-range charge separation is studied for two prototypical polymer:fullerene systems. The internal quantum efficiency (IQE) of PCDTBT:PC61BM is experimentally shown to be independent of the excitation energy. In contrast, for TQ1:PC71BM the IQE is strongly energy-dependent for excitation energies close to charge transfer (CT) electroluminescence peak maximum while it becomes energy-independent at higher excitation energies. Kinetic Monte Carlo simulations reproduce the experimental IQE and reveal that the photon energy-dependence of the IQE is governed by charge delocalization. Efficient long-range separation at excitation energies corresponding to the CT electroluminescence peak maximum or lower requires an initial separation of the hole-electron pair by ∼4-5 nm, whereas delocalization is less important for charge separation at higher photon energies. Our modeling results suggest that a phenomenological reciprocity between CT electroluminescence and external quantum efficiency does not necessarily prove that commonly employed reciprocity relations between these spectra are valid from a fundamental perspective. |
|---|---|
| Item Description: | Gesehen am 23.06.2020 |
| Physical Description: | Online Resource |
| ISSN: | 1948-7185 |
| DOI: | 10.1021/acs.jpclett.0c00945 |