Synthesis and Photo-Response of CuS Thin Films by an In Situ Multi-Deposition Process at Room Temperature: A Facile and Eco-Friendly Approach

Abstract

Uniform hexagonal covellite CuS thin films were deposited at room temperature by an in situ solution chemical reaction using copper precursor solid films as cationic source and ammonium sulfide ethanol solution as anionic reaction medium. We investigated the influence of both ethanolamine and butanol contents used in copper nitrate/ethylene glycol monomethylether (EGME) cationic solution for the preparation of copper precursor solid films, deposition cycle numbers and annealing treatment of the as-grown thin films by X-ray diffraction (XRD), FESEM, energy dispersive X-ray fluorescence EDX, transmission electron microscopy–Selected area electronic diffraction (TEM–SAED), atomic force microscopy (AFM) and ultraviolet-visible-near-infrared (UV-Vis–NIR) measurements. Photo-response of the CuS thin films was characterized by linear sweep voltammetry. The deposited CuS thin films were used to sensitize TiO 2 anodes for solar cell application. The results showed that the CuS films had two-dimension oriented, half-sheet shaped growing morphology standing disorderly but vertically to substrates, and the calculated texture coefficient TC(102) verified that the half-sheet shaped crystallites had (102) plane orientation. This in situ multi-deposition process had an average deposited rate of 9 nm per cycle, and a self-perfect function to grow smooth, uniform and 2D oriented morphology with increase in the dip-cycle numbers. The photocurrent density was 14.5 Ma/cm2 at 1 V versus Ag / AgCl electrode for the annealed CuS thin films. CuS -sensitized TiO 2 solar cells had a maximum conversion efficiency of 0.224%.