A Study On Electrodeposition Preparation Of CuInS₂ Thin Films And Their Photoelectrochemical Performance

As aⅠ-Ⅲ-Ⅵtype semiconductor compound, CuInS2 is regarded as a promising solar cell material. Its absorption coefficient reaches (1-6)×105cm-1, and it has a band gap of 1.45eV which is closed to the best band gap of the solar cell materials.Electrodeposition method for CuInS2 thin films attracts intensive attention for it can be operated at low temperature and non-vacuum condition, and is cost-effecient and suitable for large-area coating. In this paper, CuInS2 thin films were prepared by electrodepositon and sulfurization. The prepared CuInS2 thin films have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), ultraviolet/visible spectrum (UV/VIS) and so on. The main results were given as follows:1. Cu-In films have been grown on ITO glass by electrodeposition method, and then CuInS2 thin films have been obtained by sulfurization in sublimed sulfur atmosphere. The CuInS2 thin films have a direct band gap of 1.48eV, and a high absorbance (α) of 105cm-1. Chalcopyrite structure CuInS2 thin film with big and smooth surface and uniformly distributed crystal grains was obtained by this method. The best reaction condition was obtained by studying the deposition potential, the composition of the aqueous acidic solution and the effect of sulfurization process on the surface morphology and crystallization. The detailed preparation is as follow:The aqueous acidic solution is consisted of 5mM copper chloride (CuCl2),5mM indium chloride (InCl3),0.2M triethanolamine(TEA) and 0.01M Na-citrate (C6H5Na3O7·H2O) adjusted to pH=4.00 by adding sulfuric acid and sodium hydroxide. The deposition potential is-1000mV(vs.SCE) After electrodeposition, the CuInS2 thin films are submitted to thermal treatment at 450℃for 90 min in sublimed sulfur atmosphere.2. The effects of the deposition time, concentration of Na-citrate and the temperature of sulfurization on the type of conductivity, the flat band potential and incident photon to current efficiency of the CuInS2 thin films was discussed by a series of photoelectric performance test. The results shows that the prepared films was p-type semiconductor. The best reaction conditions is:The aqueous acidic solution for Cu-In thin films consisted of 5mM CuCl2, 5mM InCl3,0.2M TEA and 0.015M C6H5NasO7·H2O adjusted to pH=4.00 by adding sulfuric acid and sodium hydroxide. The deposition potential is-1000mV(vs.SCE). After electrodeposition, the CuInS2 thin films are submitted to thermal treatment at 400℃for 90 min in sublimed sulfur atmosphere.