Effect of thickness on structural, optical, and optoelectrical properties of sprayed CuInSnS4 thin films as a new absorber layer for solar cells

Abstract

Thin CuInSnS4 films, CITS of different thicknesses have been synthesized by spray pyrolysis method for the first time. These films have been deposited on pre-cleaned soda-lime glass substrates. X-ray diffraction, XRD, energy dispersive X-ray analysis, EDX, and field-emission-scanning electron microscope techniques have been utilized to characterize these CITS films. XRD-studies affirmed the polycrystalline nature of films, in addition EDX-analysis of films proves that they are stoichiometric films. Spectrophotometric studies indicate that the optical bandgap energy of films decreased from 1.88eV to 1.63eV and arose from direct allowed transitions; on contrary, the Urbach energy increases from 58 meV to 73 meV as film thickness increases. Increasing the thickness also leads to increase the absorption coefficient, extinction coefficient, and refractive index of films. Dielectric constants, and optical and electrical conductivities, along with the dispersion energies have been estimated and discussed. The dispersion energy increased (13.29eV–16.76eV), while the oscillator energy decraeses (2.98eV–2.53eV). Some linear and nonlinear optical parameters of films have been also investigated. Hot probe procedure was employed to check the semiconductor type of CuInSnS4 layers, which reveals that films have p-type conductivity. Obtained findings demonstrate that CuInSnS4 layers can be utilized as a new absorber layer for solar cells.