Efficient and Stable Planar n-i-p Perovskite Solar Cells with Negligible Hysteresis through Solution-Processed Cu2O Nanocubes as a Low-Cost Hole-Transport Material

Organic-inorganic halide perovskite solar cells (PSCs) have reached certified efficiencies of over 23 % with expensive organic hole-transporting materials. However, the use of an inorganic hole-transport layer (HTL) remains crucial as it would reduce cost combined with higher mobility and stability. In this direction, the application of Cu2O as the top layer in PSCs is still complicated owing to the difficulty of solution processing. Herein, a solution-processing method is reported for preparing Cu2O nanocubes as a p-type HTL in regular structure (n-i-p) PSCs. The controlled synthesis of Cu2O nanocubes in a size range of 60-80 nm is achieved without using any surfactants, which are usually toxic and tricky to remove. The new structure of these Cu2O nanocubes enhances the carrier mobility with preferable energy alignment to the perovskite layer and superb stability. The PSCs based on these Cu2O nanocubes HTMs could achieve an efficiency exceeding 17 % with high stability, whereas organic P3HT-based PSCs display an efficiency of 15.59 % with a poorer running stability. This indicates that Cu2O nanocubes are a promising HTM for efficient and stable PSCs.