First-Principles Calculation on Structural, Electrical and Optical Properties of APbI3 (A=CH3NH3, Cs) for Perovskites Solar Cell Applications by Using Spin-Orbit-Coupling (SOC)

Abstract

Methylammonium Lead Iodide (CH₃NH₃PbI₃) and Cesium Lead Iodide (CsPbI₃) are two of the most promising materials for perovskite solar cells (PSCs) applications because of their remarkable optimal bandgap, high absorption coefficient and broad absorption spectrum. Both materials are positioned as an active absorber layer. The structural, electronic and optical properties of PSCs are still difficult to precisely determine in their understanding and optimization. In this work by using density functional theory (DFT), structural, electronic and optical properties have been investigated and conducted by first-principles calculations using the Cambridge Serial Total Energy Package (CASTEP) within Generalized Gradient Approximation (GGA) parameterized by Perdew-Burke-Ernzerhod(PBE) calculations. First principle study has been compared in this research with the previous theoretical and experimental result. Due to variations in fabrication techniques, film quality, and experimental methods and also different type of computer codes with different bandgap that has been reported bandgap (~1.48– 1.70 eV) varies slightly for CH3NH3PbI3 and CsPbI3. The (Spin-Orbit Coupling) SOC effect has to be incorporated as it majorly lessens the bandgap by causing an evident splitting of the first degenerated conduction levels . By using SOC the best band gap has been found which is 1.34 eV and 0.97 eV for CsPbI3 and CH3NH3PbI3, respectively.With the help of the dielectric function, the optical properties were thoroughly examined through optical simulations the organic-inorganic perovskite CH3NH3PbI3 and CsPbI3 characteristic is verified. According to experimental results, the estimated static refraction index value is 2.47. This approach not only aims to resolve discrepancies in the reported data but also establishes a comprehensive understanding of these materials, advancing their potential in optoelectronic applications.