TY  - JOUR
A1  - Fritsch, Tobias
A1  - Kurpiers, Jona
A1  - Roland, Steffen
A1  - Tokmoldin, Nurlan
A1  - Shoaee, Safa
A1  - Ferron, Thomas
A1  - Collins, Brian A.
A1  - Janietz, Silvia
A1  - Vandewal, Koen
A1  - Neher, Dieter
T1  - On the interplay between CT and singlet exciton emission in organic solar cells with small driving force and its impact on voltage loss
T2  - Advanced energy materials
N2  - 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.
KW  - external quantum efficiency
KW  - organic photovoltaics
KW  - ternary blends
KW  - voltage losses
Y1  - 2022
UR  - https://publishup.uni-potsdam.de/frontdoor/index/index/docId/63727
SN  - 1614-6832
SN  - 1614-6840
VL  - 12
IS  - 31
PB  - Wiley-VCH
CY  - Weinheim
ER  -