Unveiling the MgCl2 activation on grain boundary passivation in thermally evaporated CdTe films for solar cells

Abstract

Present work exhibits influence of affordable, non-carcinogenic, low-cost, eco-friendly, non-toxic MgCl₂ activation on grain boundary passivation and physical characteristics of resistive heating-based thermally evaporated CdTe thin films (having thickness 600 nm) where prepared layers are treated with MgCl₂ followed by annealing in air atmosphere at 235 °C, 310 °C and 385 °C temperatures. All the CdTe films reveal to polycrystalline crystallographic behavior having cubic phase with (310) orientation as favored reflection. An increase in electrical resistivity is observed with activation treatment whereas crystallite size, optical energy bandgap and average surface roughness are varied in 35–45 nm, 1.43–1.60 eV and 8.6–32.7 nm ranges, respectively with activation treatment temperature. The absorbance and transmittance spectra are strongly modified with MgCl₂ activation whereas the surface topography of films indicate hillock-like structures. The PL spectra of treated CdTe films show two emission peaks positioned at ~652 nm and ~705 nm. The findings show that CdTe films activated with MgCl₂ at 310 °C might be utilized as vibrant light absorbing layers for solar cell applications.