Exploring the impact of tin addition on structural, morphology, dispersion, photovoltaic, linear, and nonlinear optical properties of thermally evaporated polycrystalline thin SnxSb2-xSe3 films

Abstract

This article focuses on preparing polycrystalline Sn_xSb_2-xSe₃ thin films (0.0 ≤ x ≤ 2.0 at.%) using the thermal evaporation process and investigating their optical and dispersion properties. These films were deposited on thoroughly-cleaned glass slides at a deposition rate of 1 nm/s, achieving a thickness of approximately 620 nm. The Sn_xSb_2-xSe₃ films were analyzed using X-ray diffraction analysis, energy-dispersive X-ray spectroscopy, field-emission scanning electron microscopy, UV–Vis-NIR spectrophotometry, and photovoltaic (I-V) measurements. The thickness (d) and refractive index (n) of thin films were determined using Swanepoel's envelope technique, with n-values at a wavelength of 800 nm increasing from 2.749 to 3.619, while d-values closely matched the controlled thickness of ≈ 620 nm. The single effective oscillator approach was successfully employed to obtain dispersion and single oscillator energies (E_d and E_o), revealing a decrease in E_d from 7.619 eV to 6.858 eV and a reduction in E_o from 4.783 eV to 4.342 eV. Various dispersion indices were calculated and analyzed using the energy values of E_d and E_o, and Sellmeier's parameters were also investigated. The static refractive index of the films increased from 2.106 to 2.276 as the Sn-content increased. The absorption coefficient ranged between 10⁴ and 10⁵cm^-1. Optical bandgap energy values, determined using Tauc's plots, decreased from 1.166 eV to 1.048 eV. The band tail width, measured using Urbach's method, increased from 0.078 eV to 0.155 eV. Additionally, the study explored various nonlinear optical parameters, which were thoroughly discussed. The hot probe method demonstrated that the Sn_xSb_2-xSe₃ films are p-type semiconductors. Conversely, the ITO/ZnS/Sn_xSb_2-xSe₃/Au heterojunction was synthesized. The photovoltaic analysis demonstrates that as the tin ratio boosts, the efficiency of heterojunction is enhanced from 3.49 % to 7.08 %. Thus, the obtained results indicate these films have many potential applications in optical, optoelectronic, clean and renewable energy, and photovoltaic fields.