Relating morphological characteristics to the open-circuit voltage of organic bulk-heterojunction solar cells

Abstract

A closed-form expression for the open-circuit voltage of organic bulk-heterojunction solar cells is derived as a function of the donor/acceptor morphology based on a spatially smoothed modelling framework. It is found that the open-circuit voltage of organic solar cells is in leading order determined by a single morphological feature: the ratio between the donor volume fraction and the specific interfacial area. Other morphological characteristics of the donor/acceptor blend, such as the connectivity of percolation pathways, do not have significant impact on the open-circuit voltage. Our findings are verified with detailed charge carrier transport simulations utilizing randomly generated donor/acceptor morphologies.