Direct Evidence of Less Charge Accumulation in Highly Durable Polymer Solar Cells Using Operando ESR Spectroscopy
DONG XUE a, Shinpei Kamiya a, Masahiko Saito b, Itaru Osaka b, Kazuhiro Marumoto a c
a Division of Materials Science, University of Tsukuba, Tsukuba, Ibaraki, 305-8573, Japan
b Hiroshima University, Japan, Hiroshima, Japan
c Tsukuba Research Center for Energy Materials Science (TREMS), University of Tsukuba, Tsukuba, Ibaraki, 305-8571, Japan
Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics
Proceedings of Asia-Pacific International Conference on Perovskite, Organic Photovoltaics and Optoelectronics (IPEROP20)
Tsukuba-shi, Japan, 2020 January 20th - 22nd
Organizers: Michio Kondo and Takurou Murakami
Poster, DONG XUE, 091
Publication date: 14th October 2019

Polymer solar cells have been extensively studied because of its low-cost, large-area production, flexible characteristics, and high power conversion efficiency (PCE). However, the internal deterioration mechanism hasn’t yet been completely clarified. Inverted-type polymer solar cells with PTzNTz have attracted much attention because of their high PCEs and durability. In this study, we report operand electron spin resonance (ESR) spectroscopy of highly durable polymer solar cells with PTzNTz to investigate the mechanism of the device-performance deterioration. The cells with PTzNTz (ITO/ZnO/PTzNTz:PC71BM/MoOx/Ag) were fabricated and sealed in an ESR sample tube in a nitrogen-filled glove box. The ESR spectra and device performance were measured simultaneously under dark or simulated solar irradiation conditions. As the duration of the light irradiation increased, the intensity of the light-induced ESR signals increased.  From the result of  fitting analysis for the light-induced ESR spectrum of the device under short-circuit conditions, the Comp. 1 is identified as a hole signal of PTzNTz, and the Comp. 2 is identified as an electron signal of PC71BM in the cell.  From the correlation between relative short-circuit current density (Jsc(t)/Jsc(0)) and the number of spins (Nspin) obtained from the light-induced ESR spectra, a clear correlation was observed between the Jsc(t)/Jsc(0) decrease and the Nspin increase. We discuss the performance deterioration mechanism on the basis of the ESR study.

This work has been partially supported by JSPS KAKENHI Grant Number JP15K13329, by JST PRESTO, by The Hitachi Global Foundation, by The MIKIYA Science And Technology Foundation, by The Futaba Foundation, and by JST ALCA Grant Number JPMJAL1603, Japan.This work has been partially supported by JSPS KAKENHI Grant Number JP15K13329, by JST PRESTO, by The Hitachi Global Foundation, by The MIKIYA Science And Technology Foundation, by The Futaba Foundation, and by JST ALCA Grant Number JPMJAL1603, Japan.

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