First-principles calculations of improving carrier mobility for β-CsPbI3

Abstract

In the past few years, inorganic perovskite CsPbI3 has attracted great interest due to high conversion efficiency in solar cells. Carrier mobility, as an important physical parameter in optoelectronic devices, directly affected power consumption. In this study, the phonon-limited mobilities of β-CsPbI3 were investigated using Boltzmann transport equation based on first-principles calculations. Using the fully relaxed lattice constants of a = 8.829/c = 6.505 Å, we obtained a mobility of μe,x=151/μe,z = 241 cm2V−1s−1 and μh,x=94/μh,z = 163 cm2V−1s−1. Longitudinal optical phonon associated with the relative vibration between Pb and I atoms was revealed to be the main scattering source, and the scattering mechanism was independent of temperature and carrier type. Biaxial compressive strain of in-plane (ab-plane) decreased mobility, which should be avoided in film growth. Since the exchange correlation functional with GGA-PBE form overestimated the lattice constants, the experimental values were used to correct the results. The band gap was mainly determined by the lattice constant of in-plane, and the mobility was extremely sensitive to the lattice constant in out-of-plane (c-axis). Using experimental lattice constants of a = 8.776/c = 6.214 Å, the mobility was improved to μe,x=503/μe,z = 1084 cm2V−1s−1 and μh,x=373/μh,z = 871 cm2V−1s−1.