Solution-processed CuBO2 hole transport layers for stable p–i–n perovskite solar cells

Abstract

Cu-based delafossite oxides have shown great potential as hole transport materials (HTMs) for perovskite solar cells (PSCs). As a member of the delafossite family, CuBO₂ has not received much attention despite its advantages of wide bandgap and high carrier mobility. Herein, a facile one-step sol–gel method is developed to fabricate CuBO₂ hole transport layers directly on FTO substrates for PSCs. Through precise optimization of the precursor concentration and pH value, flat and dense CuBO₂ films are obtained. Moreover, the influence of annealing temperature on the crystalline phase and photoelectrical properties of the CuBO₂ films is systematically investigated. Ultraviolet photoelectron spectroscopy results show that the valence band edge of the CuBO₂ film matches well with that of the perovskite layer, effectively facilitating hole extraction. The as-prepared inverted PSCs based on the CuBO₂ HTM achieve a remarkable power conversion efficiency of 18.26%. This study not only validates the potential of CuBO₂ as a promising HTM but also demonstrates a new avenue for novel inorganic HTMs in photovoltaic applications.