Effect of methanol treatment on the performance of P3HT:PC71BM bulk heterojunction solar cells with various cathodes

Abstract

The effect of an environmentally friendly methanol treatment on bulk heterojunction (BHJ) polymer solar cells based on poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) with various cathodes (Al, Ca/Al, ZnO/Al, LiF/Al) is investigated. The results show the performance of polymer solar cells with various cathodes is enhanced after methanol treatment, and the device efficiency improvement exhibits a close relationship with the type of cathodes. The power conversion efficiency of the devices with Ca/Al cathode shows the maximum enhancement with methanol treatment, and increase by as large as 27.4% compare with that of the device with Ca/Al cathode without methanol treatment. The interface dipole coming from the interaction between the methanol and the active cathode metal (Ca) in P3HT:PC71BM BHJ solar cells is the main cause of device performance enhancement.