Investigation of CuInS₂ Thin Film Formation by a Low-Temperature Chemical Deposition Method

Copper indium disulfide (CuInS(2), CIS) thin films were prepared by an alternative solution-based coating process adapted from the well-established aqueous metal salt/thiourea precursor system. The temperature for the decomposition of the precursors and the formation of CIS was lowered significantly to 130 °C by using the strongly coordinating solvent pyridine instead of the commonly used water. In addition, the influence of different annealing temperatures and concentrations of thiourea (TU) in the precursor solution on the obtained CIS samples was investigated. The films possess highly beneficial properties for photovoltaic applications, showing a chalcopyrite crystal structure, a high optical absorption (>10(4) cm(-1)) and an optical band gap between 1.45 and 1.51 eV. Chemical and morphological changes during the thin film formation were detected and explained by time-resolved simultaneous grazing incident small- and wide-angle X-ray scattering (GISAXS, GIWAXS) measurements, scanning electron microsccopy (SEM) and simultaneous thermogravimetry/mass spectroscopy (TG/MS).