Enhancing quantum efficiency of parallel-like bulk heterojunction solar cells

Abstract

We report enhanced internal quantum efficiency and absorption of parallel-like bulk heterojunction small molecular organic solar cells by inserting multi-functional layers (MFLs). The inserted MFL has an energy level between main donor and acceptor levels, assisting exciton dissociation of the charge transfer state and charge transport from active layers to electrodes. Furthermore, two donors having complementary absorption spectra yield higher and broader absorption efficiency. When a ClAlPc:C-60 layer was inserted as a MFL on CuPc:C-60, the short circuit current (J(sc)) was improved, leading to an increase of the power conversion efficiency from 2.34% to 2.71%. (C) 2013 AIP Publishing LLC.