Computational Investigation of Structural, Electronic and Optical Properties of Ternary Chalcogenide TLGaQ2 Monoclinic Compounds: a First Principle Study

Abstract

Purpose: This paper aim to investigate and predict by simulation the impact of the substitution of Q-site atom (Q꞊S, Se) on the TIGaQ2 monoclinic compounds for the first time, along the three main polarizations of the incident wave directions [100], [010] and [001].   Theoretical Framework: This study focuses mainly on ternary chalcogenide compounds TlGaQ2 (Q= S, Se) from ABQ2 family to highlight the objective resources aimed at promising prospects offered for them.   Design/Methodology/Approach: A series of ab-initio calculations based on the (PW+PP) method within the density functional theory DFT framework were carried out with CASTEP code for the simulation of their physical properties (structural, electronic-optical). The exchange correlation potential was treated within the generalized gradient approximation (GGA) implemented in the CASTEP code and expressed by the PBE functional.   Findings: The equilibrium lattice parameters are in good agreement with the available experimental results. The calculated band structure shows that are direct bandgap semiconductor nature 1.92eV (1.41eV) for TlGaS2 and TlGaSe2 respectively with a great potential for photovoltaic solar cell absorber materials. A set of optical parameters were calculated including the complex dielectric function, the reflective index, reflectivity, the absorption coefficient and loss function. The optical properties obtained revealed very interesting optical properties exhibiting strong optical absorption in UV range up to (~2x105cm-1) for both compounds making them appropriate for photovoltaic solar-cell absorber materials. Furthermore, low reflectivity and energy loss function are shown within in the visible and ultraviolet energy range, allowing them to be promising materials in several optoelectronics applications likes photosensitive devices.   Implications: All these findings results show a successful accurately prediction for chalcogenide materials behavior and will be helpful for future studies allowing a better understanding of their potential applications in modern photovoltaic technologies as well as within UV ranges for optoelectronics applications.