Formation of CuInS2 in Spray Pyrolysis Process as Simulated by Thermal Analysis

Abstract

The formation of CuInS2 thin films was studied by simulating spray pyrolysis conditions through thermogravimetric experiments performed both in air and helium. The solid precursor containing Cu, In, Cl, thiourea and H2O in a ratio 1:1:5:3:2 was obtained by evaporation of the aqueous spray pyrolysis solution. Thermal degradation of the precursor was found to be a complex process where CuInS2 is formed as the main crystalline product already at 250 °C in both atmospheres. In air, however, InOCl is also readily formed and at 650 °C In2O3 and CuO appear as final products. In thin films prepared at 320 °C the Cu:In:S ratio is correct but there are 1.5 wt.% Cl residues as shown by RBS and EDS analyses, respectively.