Optimization of linear and nonlinear optical parameters by silver halides incorporation in selenium-based thin films Se95(AgX)5

This study investigates the impact of silver-halide salts (AgCl, AgBr, and AgI) on the optical, electrical, and photoelectrical properties of chalcogenide glass-ceramic thin films, replacing selenium content. Transmission and reflectance spectra were analysed to determine optical constants, bandgap ($E_g^{opt}$), and Urbach energy (Eₑ). The optical bandgap slightly decreased (0.1 eV) for AgCl-doped films but remained stable for AgBr and AgI, while the Urbach energy significantly increased. The refractive index (n) was obtained using Swanepoel’s method, and dielectric constants (ε' and ε") were calculated. The infinite dielectric constant (ε_∞) increased from 2.45 (Se) to 3.33 (AgCl), 3.27 (AgBr), and 4.18 (AgI). The films exhibit indirect optical transitions with an optical bandgap of 1.77 to 1.89 eV, analysed using the Sellmeier and Wemple–DiDomenico (WDD) dispersion models. Further, we examined dissipation factor, energy loss functions, conductivities, relaxation time, and non-linear optical properties (n₀, χ). The results highlight the potential tunability of AgX-doped chalcogenide thin films for optoelectronic applications.