Contribution to the study of physical properties of CZTX (X=S, Se) solar materials

Abstract

In this thesis, we have studied some physical properties of Copper-Zinc-Tin-(Sulphide, Selenide) or Cu2ZnSnX4 (X=S and Se) solar materials for the kesterite (KS) and stannite (ST) types by employing first principles calculation approach, using the plane wave pseudo potential calculations (PP-PW) implemented in the CASTEP package within Density Functional Theory (DFT) and the Generalized Gradient Approximation of Wu-Cohen (GGA WC). The calculated lattice parameters are in good agreement with experimental reported data. The elastic constants are calculated for both types of both compounds using the static finite strain scheme; the pressure dependence of elastic constants is predicted. The bulk modulus, anisotropy factor, shear modulus, Young's modulus, Lame's coefficient and Poisson's ratio have been estimated from the calculated single crystalline elastic constants. The analysis of B/G ratio shows that these compounds behave as ductile. Through quasi harmonic approximation, the temperature dependence of some thermodynamic functions and lattice heat capacity of both compounds for both types have been performed.