Shape-dependent optoelectrical investigation of Cu2+xCd1−xSnS4 thin films for solar cell applications

Abstract

Cu_2+xCd_1−xSnS₄ thin films were prepared with excess Cu concentrations (x = 0, 0.02, 0.04, 0.06, 0.08 and 0.1) by a successive ionic layer adsorption and reaction (SILAR) method. The deposited films were characterized by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), UV-visible spectroscopy and I–V analysis. XRD analysis confirms the formation of tetragonal structured Cu₂CdSnS₄ thin films for all the excess Cu concentrations, while the corresponding FESEM images showed microstructural change. It may be attributed to the injection of excess Cu atoms into the Cd sites of the Cu₂CdSnS₄. The absorption coefficient is found to be greater than 10⁴ cm⁻¹ in the visible region and the bandgap energy is slightly tuned from 1.68 eV to 1.58 eV when compared to Cu₂CdSnS₄. The Cu_2.1Cd_0.9SnS₄ film showed the highest photoresponse.