Electronic and optical properties of two propounded compound in photovoltaic applications, CsPbI3 and CH3NH3PbI3: By DFT

Abstract

Halide perovskite compounds are the serious contenders for conventional materials used in photovoltaic devices that will provide a bright future for solar cell industry. Therefore, preparing a comprehensive insight about their properties is necessary. In this regard, the electronic and optical studies of two important perovskite compound CsPbI3 and CH3NH3PbI3 in the cubic phase are performed by first- principle method in Density Function Theory (DFT), using several approximations namely GGA, t-mbj and other types of t-mbj approximation with the tuned coefficient including k-mbj and new mbj approximations. In addition to utilizing different approximations, the effect of spin orbit coupling which is critical in these compounds, is evaluated in all of them to obtain realistic results. The band gaps calculated within new mbj approximation through spin orbit coupling are 1.34 eV and 1.49 eV for CsPbI3 and CH3NH3PbI3, respectively that unlike other DFT-based electronic calculations are in agreement with experimental results. Values of estimated effective masses of carriers represent lighter carriers for CH3NH3PbI3 in comparison to CsPbI3. Optical calculations of frequency dependent dielectric function confirm non isotropic property in organic- inorganic perovskite CH3NH3PbI3 and estimate value of static refraction index equal to 2.47 which is in agreement with experimental measurements.