Modeling Spontaneous Charge Transfer at Metal/Organic Hybrid Heterostructures

Abstract

Hybrid heterostructures are crucial in photovoltaics where the overall efficiencies of the materials are closely related to the level of charge transfer at their interfaces. Here, using a combined computational and experimental approach, we show that heterodyne vibrational sum frequency generation (HD-VSFG) measurements provide an effective way of monitoring the interfacial charge transfer in these heterostructures. Using ab initio quantum chemical calculations, we show that inducing regio-randomness into the organic polymer modifies the interfacial electronic states, the level of hybridization, and the electronic wave function of these materials. We present the HD-VSFG responses of the metal/P3HT heterojunctions containing both regio-regular and regio-random P3HT structures and show that the intensity of nonresonant signal is directly correlated with the computed electronic structure and the level of spontaneous charge transfer at these interfaces.