Effects of incorporation of Na in spray pyrolysed CuInS2 thin films

We investigated the effect of intentional incorporation of sodium on the structural, optical and electrical properties of Cu-poor CuInS2 thin films. Samples having a low concentration of Na exhibit better crystallinity and a remarkable increase in electrical conductivity as well as photosensitivity, compared to the undoped films. Doping of Na results in an increase of the oxygen concentration, as judged by X-ray Photoelectron Spectroscopy. However, a larger concentration of sodium (greater than 0.3%) is found to deteriorate the film properties, but the sample is still better than the undoped sample.