Understanding the effect of the carbon on the photovoltaic properties of the Cu2ZnSnS4

摘要： In this work, crystalline structure, formation energy, electronic, optical and current-voltage properties of Cu2ZnSnS4 (CZTS) with the presence of carbon (C) impurity at various sites is studied using the first-principles density functional theory (DFT) based on the generalized gradient approximation (GGA). Here, we considered possible four substitutional configurations of carbon doped CZTS supercells: Cu by C (Ccu), Cu by Zn (Czn), Sn by C (Csn) and S by C (CS). It was found that the presence of C leads to the formation of localized polarons which have dual functionality; (i) cause an increase in the scattering-limited mobility which reduces the transport efficiency, (ii) create deep acceptor level which acts as a recombination center allowing the scattering of the generated charges carriers. An enhancement in the photo-absorption is observed due to an increase in the density of states at the valence bands after the incorporation of C. This results in the efficiency enhancement by 8%. In addition, the presence of C reduces the transport efficiency and improves the photogeneration efficiency of CZTS in solar cell applications.