Investigation on thermal degradation process of polymer solar cells based on blend of PBDTTT-C and PC70BM

Abstract

The effects of thermal treatment on the photovoltaic performance of conventional and inverted polymer solar cells (PSCs) based on the combination of poly[(4,8-bis-(2-ethylhexyloxy)-benzo[1,2-b;4,5-b′]dithiophene)-2,6-diyl-alt-(4-(2-ethylhexanoyl)-thie-no[3,4-b]thiophene))-2,6-diyl] (PBDTTT-C) and [6,6]-phenyl C70-butyric acid methyl ester (PC70BM) are investigated. Thetransient photoconductivity, the absorption spectra, and the transmission electron microscopy (TEM) images have been employedto study the thermal degradation of the inverted PSCs. The degradation is attributed to the inefficient charge generation andimbalance in charge-carrier transport, which is closely associated with the morphological evolution of the active layer withprolonged heating time.