Effect of Annealing Time on Cu₂SnSe₃ Thin Films Prepared by Successive Ionic Layer Adsorption and Reaction Method

Cu₂SnSe₃ thin films—an attractive candidate for a variety of optoelectronic and solar energy applications were prepared by successive ionic layer adsorption and reaction method and the effect of annealing time on structural, optical and electrical properties were studied. X-ray diffraction analysis revealed cubic sphalerite structure of Cu₂SnSe₃ thin films at 200 °C for both 1 and 2 h of annealing time. Average crystallite sizes of the Cu₂SnSe₃ films were found to be 39.56 and 31.65 nm for 1 and 2 h, respectively. Annealed films indicated high optical absorption co-efficient values (> 10⁶ cm⁻¹) in the wavelength range of 400–800 nm. However, the annealed film (1 h) showed slightly higher absorption co-efficient in comparison to 2 h and the band gap values were found to be 1.75 and 1.83 eV for 1 and 2 h annealed films, respectively. The resistivity of Cu₂SnSe₃ film annealed for 2 h increased (41.52 Ωm) in comparison to 1 h annealed film (25.65 Ωm). Due to the increased strain in 2 h annealed film, the dislocation density was higher and hence the optical and electrical properties of the film decreased.