First-Principle Study of CsPbBr₃ and CsPbI₃ Perovskite Solar Cells

Due to the outstanding power conversion efficiency (PCE), lightweight, flexible, and low manufacturing cost, perovskite solar cells (PSCs) attract a lot of attention as the most promising candidate for the next generation of solar cells. However, the issue of poor intrinsic stability of the absorber materials and operational stability of devices remains unsolved. In this study, first-principle calculations were performed on the CsPbX₃ (X = Br or I) perovskites to provide insight into the structural, mechanical, vibrational and electronic properties of CsPbBr₃ and CsPbI₃ for their applications as active layers of solar cells. It was found that the calculated lattice parameters are in good agreement with the experimental results. CsPbBr₃ and CsPbI₃ have negative energy of formation, which implies that the materials are thermodynamically stable. The calculated band structures indicate that CsPbBr₃ and CsPbI₃ are semiconductors with direct bandgaps along R-symmetry point. Furthermore, cluster expansion and simulations of Monte-Carlo were performed to identify new possible CsPbBr_1-xI_x structures and evaluate the effect of temperature on the system. The ground-state search generated 26 new multi-component CsPbBr_1-xI_x structures, and the temperature-profile showed that the system mixes well at ∼800 K. Thus, the phase stability insight is crucial for the development of these promising perovskite solar cells.