Carrier injection dynamics in heterojunction solar cells with bipolar molecule

摘要

A boron subphthalocyanine chloride (SubPc) is a bipolar molecule and is used in hetero-junction organic solar cells. Here, we investigated the carrier injection dynamics from the donor α-sexithio-phene (6T) or acceptor C_(60) layers to the bipolar SubPc layer by means of the femtosecond time-resolved spectroscopy. We observed gradual increase of the SubPc~- (SubPc~+) species within ≈300 ps. The increases are interpreted in terms of the exciton diffusion within the 6T (C_(60)) layer and subsequent electron (hole) injection at the interface. In 6T/SubPc heterojunction, the electron injection is observed even at 80 K. The robust electron injection is ascribed to the efficient charge separation within the 6T layer under photo exciation at 400 nm.