Study of light-induced degradation of polymer: fullerene solar cells

Abstract

In the present study, the role of active and transport layer materials in the degradation mechanism is studied using different device geometries. Initially, the absorbance of the active layer materials as a function of the degradation time is compared with the photovoltaic characteristics. Also, it has been found that the hole- and electron-transport layers play a pivotal role in the degradation process for the observed decreased device efficiency. The theoretical charge-transport model complements these experimental photovoltaic parameters well. The results are attributed to the change in the quasi-Fermi level, and exciton splitting for the fresh and aged devices. These interesting and impactful results reveal a basic understanding of the degradation mechanism for the P3HT:PC₇₁BM and PTB7:PC₇₁BM blend systems and provide insights for achieving long-term stability in such solar-cell devices.