Structure, electronic and optical properties of chalcopyrite semiconductor AgTiX2 (X = S, Se, Te): A density functional theory study

Abstract The structure, electronic and optical properties of chalcopyrite-type semiconductor material AgTiX2 (X = S, Se, Te) are investigated invoking Density Functional Theory (DFT). The computed Highest Occupied Molecular Orbital (HOMO)-Lowest Unoccupied Molecular Orbital (LUMO) energy gap of AgTiX2 molecule with and without 4f function on Ag is in the range of 2.319 eV – 3.211 eV and 2.092 eV – 3.056 eV respectively. It establishes that AgTiX2 can be used as potential candidate for optoelectronic and photovoltaic applications, especially in solar cells. Result analysis reveals that AgTiS2, having a rectangular geometry with C2v point group and doublet spin multiplicity, is the most stable system with maximum HOMO-LUMO gap. Our calculated DFT based global descriptors and spectral analysis transpires that HOMO-LUMO energy gap, harmonic frequency and intensity of IR and Raman spectra decreases from AgTiS2 to AgTiSe2 to AgTiTe2. A strong correlation is established between DFT based global descriptors and HOMO-LUMO gap from this analysis.