TY  - JOUR
A1  - Ran, Niva A.
A1  - Love, John A.
A1  - Heiber, Michael C.
A1  - Jiao, Xuechen
A1  - Hughes, Michael P.
A1  - Karki, Akchheta
A1  - Wang, Ming
A1  - Brus, Viktor V.
A1  - Wang, Hengbin
A1  - Neher, Dieter
A1  - Ade, Harald
A1  - Bazan, Guillermo C.
A1  - Thuc-Quyen Nguyen, 
T1  - Charge generation and recombination in an organic solar cell with low energetic offsets
JF  - dvanced energy materials
N2  - Organic bulk heterojunction (BHJ) solar cells require energetic offsets between the donor and acceptor to obtain high short-circuit currents (J(SC)) and fill factors (FF). However, it is necessary to reduce the energetic offsets to achieve high open-circuit voltages (V-OC). Recently, reports have highlighted BHJ blends that are pushing at the accepted limits of energetic offsets necessary for high efficiency. Unfortunately, most of these BHJs have modest FF values. How the energetic offset impacts the solar cell characteristics thus remains poorly understood. Here, a comprehensive characterization of the losses in a polymer:fullerene BHJ blend, PIPCP:phenyl-C61-butyric acid methyl ester (PC61BM), that achieves a high V-OC (0.9 V) with very low energy losses (E-loss = 0.52 eV) from the energy of absorbed photons, a respectable J(SC) (13 mA cm(-2)), but a limited FF (54%) is reported. Despite the low energetic offset, the system does not suffer from field-dependent generation and instead it is characterized by very fast nongeminate recombination and the presence of shallow traps. The charge-carrier losses are attributed to suboptimal morphology due to high miscibility between PIPCP and PC61BM. These results hold promise that given the appropriate morphology, the J(SC), V-OC, and FF can all be improved, even with very low energetic offsets.
KW  - energetic offset
KW  - fill factor
KW  - morphology
KW  - organic solar cells
KW  - recombination
Y1  - 2018
U6  - https://doi.org/10.1002/aenm.201701073
SN  - 1614-6832
SN  - 1614-6840
VL  - 8
IS  - 5
PB  - Wiley-VCH
CY  - Weinheim
ER  -