Crystal and electronic structure studies on transparent conducting nitrides A ₃N₂ (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 Sn 3 N 4 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 Sn 3 N 2 and Sn 3 N 4 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 Mg 3 N 2 from GGA calculation. For Sn 3 N 4 band gaps of 0.24 eV and 0.7 eV are obtained using GGA and LDA calculations, respectively, whereas GGA+ U was used to obtain band gap in Zn 3 N 2 . 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. Zn 3 N 2 is found to have the possibility for n -type as well as p -type doping because of the low effective mass of electrons and holes compared to other studied nitrides. Hence, Zn 3 N 2 has suitable conductive properties to be used as a solar cell material.