Ab initio study on electronic and optical properties of Cu₂NiGeS₄ for photovoltaic applications

In this paper, first principle calculations of Cu₂NiGeS₄ (CNGS) are carried out to explore the structural, electronic and optical properties of kesterite compound. Both mBJ+U and HSE potentials are used to calculate the band gap energy. The first approach gives a value of 1.78 eV and the second one a value of 1.76 eV. Our numerical simulation shows that the CNGS exhibits a remarkable high absorption coefficient of the order of 10⁴ cm⁻¹, leading to a promising absorber material for photovoltaic devices. Additional optical properties such as refraction index and dielectric function are also calculated in this work. Furthermore, CNGS-based solar cell simulation was performed through SCAPS software. The calculated values of short-circuit current density J_sc, open-circuit voltage V_oc, Fill factor FF and power conversion efficiency show that CNGS can be a potential candidate for solar cell application.