On the Role of Bathocuproine in Organic Photovoltaic Cells



The effect of bathocuproine (BCP) on the optical and electrical properties of organic planar heterojunction photovoltaic cells is quantified by current–voltage characterization under 1 sun AM 1.5D simulated solar illumination and spectral response at short-circuit conditions. By inserting a 10 nm BCP layer in an indium tin oxide (ITO)/subphthalocyanine (SubPc)/buckminsterfullerene (C60)/BCP/Al thin-film structure, an increase in power-conversion efficiency from 0.05 to 3.0% is observed, mostly reflected in the enhanced open-circuit voltage up to 920 mV. Furthermore, the incorporation of a 10-nm BCP layer in an ITO/C60/BCP/Al structure leads to an increase in built-in potential from 250 to 850 mV, as demonstrated by electroabsorption. It is argued that BCP passivates C60 such that a 10-nm layer provides a sufficient buffer layer that prohibits Al contacting the C60 where it would otherwise create donor states.