Characterization of Spray Pyrolysed CuInS2 Thin Films

An indigenously developed chemical spray pyrolysis system was used to deposit polycrystalline CuInS2 thin films. It was found that smaller spray rate results in films with better crystallinity and lower resistivity. Increase in surface roughness of the films was observed for higher spray rates. Variations in film stoichiometry with composition of spray solution were analyzed along with its opto-electronic and structural properties. Sulfur rich starting solution with equimolar ratio of copper and indium resulted in nearly stoichiometric p-type CuInS2. Type conversion, modification of surface morphology and wide range of opto-electronic properties could be achieved by large off-stoichiometric variations. Temperature dependent conductivity study was used for defect analysis and levels at 436 meV, 294 meV, 131 meV, 76 meV and 50 meV were identified.