On the function of a bathocuproine buffer layer in organic photovoltaic cells

The role of bathocuproine (BCP) buffer layer inserted between active layer and Al contact in photovoltaic cells based on phthalocyanine (Pc) and C60 was investigated. Photoluminescence (PL) experiments show exciton quenching at the C60–Al interface to be strongly reduced by inserting BCP. Current-voltage characteristics of photovoltaic cells with planar geometry front electrode/Pc∕C60∕BCP∕Al show that BCP dramatically improves electron transport out of the C60 film into the Al electrode. The tenfold increase in power conversion efficiency (η) with BCP can mostly be attributed to the latter effect. BCP does not improve η in photovoltaic cells with blend film geometry front electrode/Pc:C60∕Al.