Structural, Electronic, Stability, and Optical Properties of CsPb1-xSnxIBr2 Perovskites: A First-Principles Investigation

Recently, exploration of stabler and lead-free perovskite absorbers with better cost-effective processability and prominent light harvesting capacity has attracted extensive attentions. Inorganic Cs-based halide perovskites are outstanding in enormous functional materials for their improved long-term stability. In this study, we performed a first-principles investigation based on density functional theory to explore the structural, electronic, stability, and optical properties of both cubic (alpha) and orthorhombic (gamma) phases CsPb1-xSnxIBr2 (x = 0, 0. 25, 0.5, and 0.75). According to our calculations, the energy conversion properties tend to be controlled by the new hybrid states of Sn2+ and Pb2+ with doping of Sn atoms. The calculated formation energies, phase stability diagram analysis, electron localization function, and charge density distribution of these mixed pervoskites demonstrate that they are the most stable among all of the doped CsP1-xSnxIBr2 perovskite series. Notablely, alpha-CsPb0.25Sn0.75IBr2 and gamma-CsPb0.75Sn0.25IBr2 show the strongest absorption within the visible light range, maximum amount of photons absorbent, remarkably stability, and suitable band gaps. Our study provides theoretical insight into the rationale design of highly efficient and stable inorganic halide perovskite photovoltaic devices and sheds a new light on designing and synthesizing the next generation of photovoltaic materials.