Influence of silver doping on physical properties of sprayed In2S3 films for solar cells application

Abstract

A set of silver-doped indium sulphide (In2S3:Ag) thin films were deposited by spray pyrolysis technique, at 350 degrees C, to analyze the effects of the Ag doping on the physical properties of the films. Within the limits of the analyzed dopant concentration, X-ray diffraction (XRD) revealed the polycrystalline nature of the films, crystalizing in the beta-In2S3 cubic phase, regardless the level of doping. Both XRD and Raman spectroscopy confirmed the absence of secondary phases. Optical absorption spectra evidenced that the films are opaque to ultraviolet radiation, but transparent in visible and near infrared regions of the electromagnetic spectrum. According to absorption and extinction coefficients variations, the films are smooth and homogeneous. The forbidden bandgap (E-g) increases with increasing Ag concentration. Photoluminescence measurements reveal that the films exhibit seven emissions related to In2S3 defects. The films are semiconductor and the transport phenomena are assisted via small polaron hopping. The photovoltaic effect in Ag/In2S3(n)/Si(p)/Ag is confirmed by I-V characterization in dark and under illumination.