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

Abstract
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 (J_) and open-circuit voltage (V_) . The power conversion efficiency (η_p) of the device with MCS interface (Cu-phthalocyanine/C_ and pentacene/C_) is enhanced compared with that of the device with single charge separation interface (pentacene/C_). The enhancement of η_p is attributable to the increase in V_ with maintaining the J_. By using Zn-phthalocyanine, which possesses longer excited lifetime compared with Cu-phthalocyanine, both J_ and V_ have been improved simultaneously and the η_p reaches 2.04%