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 (J(sc)) and open-circuit voltage (V-oc). The power conversion efficiency (eta(p)) of the device with MCS interface (Cu-phthalocyanine/C-60 and pentacene/C-60) is enhanced compared with that of the device with single charge separation interface (pentacene/C-60). The enhancement of eta(p) is attributable to the increase in V-oc with maintaining the J(sc). By using Zn-phthalocyanine, which possesses longer excited lifetime compared with Cu-phthalocyanine, both J(sc) and V-oc have been improved simultaneously and the eta(p) reaches 2.04%. (C) 2007 American Institute of Physics.