Crystal and electronic structure studies on transparent conducting nitrides A3N2 (A = Mg, Zn and Sn) and Sn3N4

Finding potential materials for solar cell applications is essential to reduce cost and enhance efficiency. We have employed Density Functional Theory (DFT) based calculations for novel nitrides of type A(3)N(2) (A = Mg, Zn ans Sn) and Sn3N4 to find the ground state crystal and electronic structure. The structural parameters optimized by theoretical calculation are in good agreement with the experimental parameters. In order to obtain Sn3N4 and Sn3N4 experimentally, we are suggesting a new synthesis route from the calculated enthalpy of formation. The studied nitrides exhibit semiconductor behavior with direct band gaps. Band gap of 1.7 eV is obtained for Mg3N2 from GGA calculation. For Sn3N4 band gaps of 0.24 eV and 0.7 eV are obtained using GGA and LDA calculations, respectively, whereas GGA+Uwas used to obtain band gap in Zn3N2. The bonding behavior is analyzed in detail by using charge density and electron localization function plots. In addition, COHP (Crystal Orbital Hamiltonian Population) is utilized to retrieve bond strength values. Charge transfer from cation to anion decreases from Mg to Sn and correspondingly bond strength between the metal and Nitrogen atoms is also found to increase from Mg to Sn, which indicates increase in covalent nature of bonding from Mg to Sn. Zn3N2 is found to have the possibility for n-type as well asp-type doping because of the low effective mass of electrons and holes compared to other studied nitrides. Hence, Zn3N2 has suitable conductive properties to be used as a solar cell material.