Theoretical Study on the Carrier Mobility and Optical Properties of CsPbI₃ by DFT

The advantages of organic-inorganic hybrid halide perovskites and related materials, such as high absorption coefficient, appropriate band gap, excellent carrier mobility, and long carrier life, provide the possibility for the preparation of low-cost and high-efficiency solar cell materials. Among the inorganic materials, CsPbI₃ is paid more attention to by researchers as CsPbI₃ has incomparable advantages. In this paper, based on density functional theory (DFT), we first analyze the crystal structure, electronic properties, and work function of two common bulk structures of CsPbI₃ and their slices, and then, we study the carrier mobility, exciton binding energy, and light absorption coefficient. Considering that CsPbI₃ contains heavy elements, the spin-orbit coupling (SOC) effect was also considered in the calculation. The highest mobility is that electrons of the cubic structure reach 1399 cm² V^-1 S^-1 after considering the SOC effect, which is equal to that of traditional solar cells (such as Si-based, PbSe, and PbTe). The lowest exciton binding energy is 101 meV in the cubic bulk structure, which is beneficial to the separation of photogenerated carriers. In the visible region, the absorption coefficient of the cubic structure is the best among all structures, reaching 10⁵ cm^-1. Through the study of mobility, exciton binding energy, and light absorption coefficient, it is found that the cubic bulk structure in all structures of CsPbI₃ has the best photoelectric performance. This paper can provide some guidance for the experimental preparation of CsPbI₃ as a potential high-efficiency solar cell material.