Photoconductivity of C₆₀ as an Origin of Bias‐Dependent Photocurrent in Organic Photovoltaics

Abstract

Abstract The bulk‐ionized photoconductivity of C 60 is reported as an origin of the bias‐dependent linear change of the photocurrent in copper phthalocyanine (CuPc)/C 60 planar heterojunction solar cells, based on the observation of the variation of the bias‐dependent photocurrent on excitation wavelengths and the thickness‐dependent photocurrent of the C 60 layer. A theoretical model, which is a combination of the Braun‐Onsager model for the dissociation of excitons at the donor/acceptor interface and the Onsager model for the bulk ionization of excitons in the C 60 layer, describes the bias‐dependent photocurrent in the devices very well. The bulk‐ionized photoconductivity of C 60 must generally contribute to the photocurrent in organic photovoltaics, since fullerene and fullerene derivatives are widely used in these devices.