Monovalent Copper Cation Doping Enables High-Performance CsPbIBr₂-Based All-Inorganic Perovskite Solar Cells

Organic-inorganic perovskite solar cells (PSCs) have delivered the highest power conversion efficiency (PCE) of 25.7% currently, but they are unfortunately limited by several key issues, such as inferior humid and thermal stability, significantly retarding their widespread application. To tackle the instability issue, all-inorganic PSCs have attracted increasing interest due to superior structural, humid and high-temperature stability to their organic-inorganic counterparts. Nevertheless, all-inorganic PSCs with typical CsPbIBr₂ perovskite as light absorbers suffer from much inferior PCEs to those of organic-inorganic PSCs. Functional doping is regarded as a simple and useful strategy to improve the PCEs of CsPbIBr₂-based all-inorganic PSCs. Herein, we report a monovalent copper cation (Cu⁺)-doping strategy to boost the performance of CsPbIBr₂-based PSCs by increasing the grain sizes and improving the CsPbIBr₂ film quality, reducing the defect density, inhibiting the carrier recombination and constructing proper energy level alignment. Consequently, the device with optimized Cu⁺-doping concentration generates a much better PCE of 9.11% than the pristine cell (7.24%). Moreover, the Cu⁺ doping also remarkably enhances the humid and thermal durability of CsPbIBr₂-based PSCs with suppressed hysteresis. The current study provides a simple and useful strategy to enhance the PCE and the durability of CsPbIBr₂-based PSCs, which can promote the practical application of perovskite photovoltaics.