Control of open-circuit voltage in organic photovoltaic cells by inserting an ultrathin metal-phthalocyanine layer

The authors develop organic photovoltaic cells with multicharge separation (MCS) interfaces by inserting a very thin layer of metal phthalocyanine. The devices with MCS interface allow one to control short-circuit current density (Jsc) and open-circuit voltage (Voc). The power conversion efficiency (p) of the device with MCS interface (Cu-phthalocyanine/ C60 and pentacene C60) is enhanced compared with that of the device with single charge separation interface (pentacene/ C60). The enhancement of p is attributable to the increase in Voc with maintaining the Jsc. By using Zn-phthalocyanine, which possesses longer excited lifetime compared with Cu-phthalocyanine, both Jsc and Voc have been improved simultaneously and the p reaches 2.04%.