Comprehensive DFT investigation of ternary thallium tetragonal crystals: assessing their viability for solar cell applications

Abstract

To ascertain the suitability of the TlInX2 (X = S, Se, Te) tetragonal structures for photovoltaic applications, first-principles calculations were carried out using the pseudopotential plane wave method to assess the structural, electronic, elastic, and optical characteristics of the considered compounds via the DFT software CASTEP. For all three compounds, our calculated structural parameters were in excellent agreement with both the experimental and previous theoretical results. Our calculations provided the first predicted elastic constants for the TlInS2, TlInSe2 and TlInTe2 compounds. The three tetragonal systems were mechanically stable and exhibited pronounced and noticeable elastic anisotropy. Analysis of the optical properties revealed that TlInX2 (X = S, Se, Te) exhibited distinct absorption in the ultraviolet radiation range and pronounced optical anisotropy. The calculated bandgap values obtained using the HSE06 hybrid functional were 1.68 eV, 1.38 eV, and 1.36 eV for TlInS2, TlInSe2 and TlInTe2, respectively. These findings are of significant interest because they categorize all three compounds as promising candidates for use in photovoltaic cell applications.