Precursor concentration effect on the properties of ZnInSE4 layers grown by chemical bath deposition

ZnIn2Se4 (ZIS) films were grown by chemical bath method and the effects of precursor concentration (PC) on the chemical and physical properties were investigated for the first time. The layers were grown on Corning 7059 glass substrates using equimolar aqueous solutions of zinc chloride, indium tri-chloride and sodium selenite as precursors. The deposition was carried out at different PC values that vary in the range, 0.01 - 0.075 M at a constant bath temperature of 80 °C and deposition time of 90 min. The structural studies showed nanocrystalline nature of the films with the (112) preferred orientation. The crystallite size varied in the range, 54 – 125 Å. The composition analysis indicated O and Cl in addition to Zn, In and Se in the films. The optical transmittance changed with PC and layers with PC=0.05 M had the transmittance, >75% in the visible range. The energy band gap of the films varied in the range, 2.91 - 3.09 eV with change of PC. FTIR studies were undertaken to identify the adsorbed functional groups on the surface of the films and photoluminescence spectra revealed the presence of defect states in the films. A detailed analysis of these properties are reported and discussed.