Facile solution-controlled growth of CuInS2 thin films on FTO and TiO2/FTO glass substrates for photovoltaic application

This paper reports on the preparation of two thin films (CuInS2/FTO and CuInS2/TiO2/FTO) by a facile solvothermal method and their photovoltaic properties. Instrumental measurements including X-ray diffraction (XRD), inductively coupled plasma emission spectroscopy (ICP), scanning electron microscopy (SEM), and UV-vis spectra have been used to characterize the obtained CuInS2 thin films. The results show that the CuInS2 films deposited on fluorine-doped tin oxide-coated (FTO) conductive glass substrates are composed of nanoplates and microspheres. The thickness of the CuInS2/FTO films can be adjusted from 1 mu m to 8 mu m by controlling the solution concentration of the reactants. While, the prepared 10 mu m-thick CuInS2 film on the TiO2 film substrate consists of nanoplates. The UV-vis absorption spectra reveal that the CuInS2 thin films have a strong absorption around 400-850nm and the band-gap energy is tunable in the range of 1.45-1.61 eV with the variation of Cu/In ratio from 1.20 to 0.90. Furthermore, two types of thin film solar cells, which have an effective area of 0.25 cm(2) and possess separately the top-down composition of Ag/CdS/CuInS2/FTO and FTO/TiO2/CuInS2/Au, were fabricated after heat-treatment to evaluate their photovoltaic properties and the corresponding conversion efficiency is 0.33% and 0.29% under AM 1.5 irradiation (100 mW cm(-2)), respectively (C) 2009 Elsevier B.V. All rights reserved.