Bandgap tuning and analysis of the electronic structure of the Cu2NiXS4 (X=Sn, Ge, Si) system: mBJ accuracy with DFT expense

The energy bands and band gaps of Cu₂NiXS₄ (X ​= ​Sn, Ge, Si) semiconductor materials have been studied and analyzed by using quantum-chemical calculations within the DFT framework. Using different exchange-correlation functionals, the energy gaps of the studied systems were estimated and determined, and their band structure were studied in detail. Based on the results of spin-polarized and spin-orbit mBJ-calculations, bands of t2g states and direct band gaps with values of 1.32, 1.56, and 2.58 ​ eV, were found for Cu₂NiSnS₄, Cu₂NiGeS₄, and Cu₂NiSiS₄, respectively, indicating the suitability of these materials as a suitable light-absorbing layer for a new generation solar cells.