TY  - JOUR
A1  - Le Quang Phuong, 
A1  - Hosseini, Seyed Mehrdad
A1  - Koh, Chang Woo
A1  - Woo, Han Young
A1  - Shoaee, Safa
T1  - Measuring Competing Recombination Losses in a Significantly Reduced Langevin System by Steady-State Photoinduced Absorption and Photocurrent Spectroscopy
JF  - The journal of physical chemistry : C, Nanomaterials and interfaces
N2  - Understanding and disentangling photophysical properties of long-lived photoexcitations in bulk heterojunction (BHJ) solar cells, which contribute mostly to photocurrent, provide essential guidelines to their improvement. However, to construct improved physical models, their rational design relies on reliable measurement techniques for charge recombination. Here, we combine photocurrent and photoinduced absorption spectroscopy (PCPIA) to directly probe the free carrier concentration and investigate loss mechanisms of long-lived excitations in nearly 10% efficient PPDT2FBT/PC70BM BHJ solar cells under steady-state operational conditions. From the PCPIA data obtained under open- circuit and short-circuit conditions, the absorption cross section and the concentration of photoexcitations are obtained. This material system exhibits an exceptionally low bimolecular recombination rate, about 300 times smaller than the diffusion-controlled electron and hole encounter rate. Furthermore, we observe that the fill factor is limited by losses originating from long-lived photoexcitations undergoing dispersive bimolecular recombination.
Y1  - 2019
U6  - https://doi.org/10.1021/acs.jpcc.9b08901
SN  - 1932-7447
SN  - 1932-7455
VL  - 123
IS  - 45
SP  - 27417
EP  - 27422
PB  - American Chemical Society
CY  - Washington
ER  -