Multifunctional CZTS thin films: Structural, optoelectrical, electrical and photovoltaic properties

Highlights: • Cu₂ZnSnS₄ thin films are prepared by CBD technique. • XRD revealed the polycrystalline nature with kieserite structure. • HRTEM shows that the films are homogenous and the grains are definable. • Optical parameters are determined using transmission & reflection spectra. • The fabricated device reveals an efficiency about 3.37%. High-quality Cu₂ZnSnS₄ (CZTS) thin films of different thicknesses (240 nm–418 nm) have been prepared onto pre-cleaned glass substrates using a low-cost chemical bath deposition technique. Influence of deposition conditions on the variation of the structural, optical, optoelectrical and electrical properties of the CZTS films has been inspected. The XRD patterns revealed that CZTS thin films exhibited a polycrystalline nature and follow the kieserite crystal structure. The studied films have exhibited direct energy gap transition that decreased from 1.54 to 1.48 eV. Profound analysis has been made to investigate the variation of the optical and optoelectrical properties of CZTS as a function of deposition time. A prominent increase in the nonlinear parameters has been noticed with the increase in the deposition time. This finding could shed lights on the possibility of using CZTS in nonlinear devices. The variation of the DC conductivity with temperature for the CZTS thin films has been discussed. The values of the activation energies have been decreased with increasing the film thickness which confirms the increase in film uniformity. Good correlations have been established between the structural aspects of the films to their optical and optoelectrical parameters. Cu₂ZnSnS₄ film (418 nm) has been selected to be utilized in fabricating the Al/n-Si/P-CZTS/Au heterojunction. Photovoltaic behavior was observed for the fabricated device which had a solar conversion efficiency of 3.37%.