Structural properties of sprayed CuInSSe thin films grown using different S/Se ionic ratios

Abstract

We have grown nanocrystalline CuInSSe thin films on glass substrates using the spray pyrolysis technique at different S/Se ionic ratios 0.4 and 0.6. The CuInSSe films were co-deposited from aqueous solutions containing CuCl2, InCl3, thiourea and SeO2. The pH of the precursor solutions was kept at 10. Ethanolamine was used as an additive and the CuInSSe films were deposited at the constant temperature 300°C. The films were characterized by X-ray diffraction (XRD), and the results indicate that the films are single phase, polycrystalline having the chalcopyrite structure. The hot probe method indicates that the films are p-type in conductivity. Optical studies show that the optical band gap values are 1.25 eV and 1.36 eV for films grown from spray solutions having S/Se ionic ratios 0.4 and 0.6 respectively. The interesting result of this paper is that the optical band gap value (1.25 eV) is very close to the optimum band gap for terrestrial photovoltaic solar energy conversion. The Debye Scherrer formula applied to the XRD patterns show that the average crystallite size of the films is in the range 10 to 20 nm.