CuGaO₂ Nanosheet Arrays as the Hole-Transport Layer in Inverted Perovskite Solar Cells

Currently, perovskite solar cells (PSCs) have achieved photoelectric conversion efficiencies (PCEs) comparable to silicon-based and GaAs solar cells. However, PSCs show relatively poor long-term stability, which inhibits their commercialization. Therefore, researchers have turned to inorganic hole-transport materials (HTMs) with more stable chemical properties, such as CuGaO2. It is well known that inorganic HTMs have uneven coverage and show agglomeration in thin films. This study is the first report of growing CuGaO2 nanosheet arrays (CGO arrays) using a simple, low-cost, and reproducible microwave hydrothermal method. This material acts as a hole-transport layer for inverted PSCs, which increases the hole extraction area and efficiency. Remarkably, the devices based on the CGO arrays showed excellent performance in terms of thermal stability and moisture corrosion resistance. After thermal aging in the glovebox for 240 h, the device still maintained more than 78% of the initial efficiency. After 400 h of storage in an environment with a humidity of 50–80%, the device retained more than 83% of its initial efficiency. Consequently, in this study, the CGO arrays were able to reduce the impact of the external factors on the device life of PSCs to maintain an efficient and stable output.