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 delafossite family, CuBO2 has not received much attention despite it owns advantages of wider bandgap and higher carrier mobility. Here, 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 precursor concentration and pH value, the 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 result shows that the valence band edge the CuBO2 film matches well with the perovskite layer, which effectively facilitate the hole extraction. The as-prepared inverted PSCs based on 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 the novel inorganic HTMs in photovoltaic applications.