Fullerene derivative layer induced phase separation and charge transport improvement for inverted polymer solar cells

Abstract

The phase separation of donor and acceptor in bulk-heterojunction plays an important role on the exciton dissociation and charge carrier transport, which decides the performance of organic solar cells (OSCs). In this paper, the thin [6,6]-Phenyl-C71-butyric acid methyl ester (PC71BM) layer was incorporated as interlayer between active layer and the polyethylenemine electron transport layer of OSCs to realize high efficiency. Both a high short-circuit current density and fill factor were achieved, resulting in a power conversion efficiency up to 9.17% for the optimal device. The incorporation of PC71BM layer not only induced vertical phase separation of active layer to improve exciton dissociation and charge transfer but also modified surface morphology to increase light absorption of the active layer. This study offers a simple and lost cost strategy to improve performance of OSCs.