Controlling the crystallite size and influence of the film thickness on the optical and electrical characteristics of nanocrystalline Cu2S films

Abstract In this work, Cu 2 S nanocrystalline films have been successfully prepared using dip-coating technique. The stoichiometry and the structural characteristics of the prepared films were characterized by energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD), respectively. The surface morphology of the deposited Cu 2 S film was studied using both the scanning electron microscopy (SEM) and the atomic force microscopy (AFM). The SEM and AFM images indicate that the prepared Cu 2 S films are characterized by a well-dispersed and highly dense with spherical like-shaped aggregates of size in the nano scale. The optical absorption measurements indicate that the Cu 2 S nanoparticles have a direct band gap of 2.92 eV. The dispersion and absorption parameters such as the dispersion energy, oscillating energy, real and imaginary dielectric constants and dissipation factor were calculated within a wide wavelength range of the spectrum that indicates the suitability of the deposited films as solar absorber using this technique. The dark electrical resistivity ( ρ ) measurements were carried out at different temperatures in the range 312–440 K. These results confirm the semiconducting characteristic of the prepared Cu 2 S films. Moreover, two activation energies were obtained that indicate the presence of two dominating conduction mechanisms in these temperature ranges. The bulk electrical resistivity ( ρ B ) and the mean free path ( l 0 ) of charge carriers were estimated from the resistivity-thickness dependence. The heterojunction device of n-ZnCdS/p-Cu 2 S behaves good rectifying property. The photovoltaic characteristic of the heterojunction device using the current–voltage characteristic under illumination of 100 mW/cm 2 was also observed. Discussion of the obtained results and their comparison with the previous published data were also considered.