CuPbX₃ and AgPbX₃ (X = I, Br, Cl) Inorganic Perovskites for Solar cell Applications

Background: One of the possible solutions to the world’s rapidly increasing energy demand is the development of new photovoltaic devices and photoelectrochemical cells with improved light absorption. This requires developing new semiconductor materials with an appropriate band gap that can absorb a large part of the solar spectrum while being stable in both ambient and aqueous environments. Methods: Here, we showed the computational identification of relevant fully inorganic ternary perovskite materials based on electronic structure calculations. Our first-principles calculations were based on DFT as implemented in the VASP program. The identification was based on an efficient and reliable way of calculating semiconductor band gaps. Result: We found that these materials are suitable for solar cell purposes, since their optical band gap ranges from 1.54 to 2.33 eV according to the computational calculation and from 1.42 to 1.93 eV according to the experimentally determined result, which is similar to the CH₃NH₃PbI₃ hybrid perovskites. Conclusions: The outcome of the identification includes new ABX₃-type materials, i.e., CuPbI₃, CuPbBr₃, CuPbCl₃ and families of AgPbX₃, which warrant further experimental investigations. These materials are not sensitive to moisture, temperature and air and are hence expected to form stable solar cells. Cu and Ag cations are involved in the band structure, narrowing the bandgap, which will lead to high-efficiency solar cells with low loss power conversion efficiency owing to the involvement of the 4s orbital. The Cu 4s is a partially filled orbital creating a partially filled valence band owing to the 4s¹3d¹⁰ electron configuration, which is absolutely crucial for metallic behavior in CuPbX₃ materials. Since it ensures that there are unoccupied energy levels at an infinitesimally small energy above the highest occupied level, solar cell devices made of these semiconductors are less affected by defects and have efficient charge transfer. In addition to this, defect passivation strategies are highly useful in constructing solar cells.