Photodeposited Polyamorphous CuOx Hole-Transport Layers in Organic Photovoltaics

Abstract

Hole-selective charge-transport layers are an important part of modern thin-film electronics, serving to direct electron flow and prevent leakage current. Crystalline metal-oxide hole-transport layers (HTLs) such as NiO and CuOx exhibit high performance and stability. However, they are traditionally not amenable to scalable and sustainable solution-processing techniques. Conversely, amorphous metal oxides are much more readily prepared by low-temperature solution processing methods but often lack the charge-transport properties of crystalline semiconductors. Herein, we report the fabrication of amorphous a-CuOx thin films from commercially available starting materials using a simple UV-based thin-film deposition method. Subsequent thermal annealing of the a-CuOx induces an amorphous-to-amorphous phase transition, resulting in p-type semiconducting behavior. The resulting thin films were used as HTLs in organic photovoltaic devices with power conversion efficiencies comparable to those fabricated with PEDOT:PSS.