Promoting the Efficiency and Stability of CsPbIBr₂-Based All-Inorganic Perovskite Solar Cells through a Functional Cu²⁺ Doping Strategy

Although organic-inorganic halide perovskite solar cells (PSCs) have shown dramatically enhanced power conversion efficiencies (PCEs) in the last decade, their long-term stability is still a critical challenge for commercialization. To address this issue, tremendous research efforts have been devoted to exploring all-inorganic PSCs because of their intrinsically high structural stability. Among them, CsPbIBr₂-based all-inorganic PSCs have drawn increasing attention owing to their suitable band gap and favorable stability. However, the PCEs of CsPbIBr₂-based PSCs are still far from those of their organic-inorganic counterparts, thus inhibiting their practical applications. Herein, we demonstrate that by simply doping an appropriate amount of Cu²⁺ into a CsPbIBr₂ perovskite lattice (0.5 at. % to Pb²⁺), the perovskite crystallinity and grain size are increased, the perovskite film morphology is improved, the energy level alignment is optimized, and the trap density and charge recombination are reduced. As a consequence, a decent PCE improvement from 7.81 to 10.4% is achieved along with an enhancement ratio of 33% with a CsPbIBr₂-based PSC. Furthermore, the long-term stability of CsPbIBr₂-based PSCs against moisture and heat also remarkably improved by Cu²⁺ doping. This work provides a facile and effective route to improve the PCE and long-term stability of CsPbIBr₂-based all-inorganic PSCs.