Optimization of growth of ternary CuInS2 thin films by ionic reactions in alkaline chemical bath as n-type photoabsorber layer

Thin films of n-type CuInS2 (CIS) have been grown onto a indium–tin-oxide glass substrates using the ionic reactions in alkaline chemical bath at 40 °C temperature. The alkaline cationic and anionic in single precursor solution is obtained by dissolving CuSO4 (0.02 M), InCl3 (0.02 M), citric acid (0.05 M) and NH2–CS–NH2 (0.02 M) in deionized water at higher pH value (11). In order to achieve uniformity of the films an appropriate triethanolamine has been added in the precursor solution. The as-deposited CIS films are annealed in air at 150 °C for 30 min in air. The structure, morphology, composition and chemical bonding are studied by X-ray diffraction, scanning electron microscopy, energy dispersive analysis of X-ray and X-ray photoelectron spectroscopy, respectively. The substrate surface is well-covered by dense nanorods type morphology with indium-rich stoichiometry. The thickness of prepared CuInS2 layer is about 200 nm and spherical grains of about 20–200 nm are agglomerated over substrate surface. The thermoelectric power, dark and light I–V characteristics are used for electrical measurements. The type of conductivity is changed from n to p after etching in an aqueous ammonia solution.