Investigation on CuInS2 Films with Wurtzite Structure Prepared from Nitrates

Abstract

The phases, morphology and band gap of CuInS2 films with wurtzite structure prepared by spin-coating and chemical co-reduction method were studied. Experimental results show that, CuInS2 films with wurtzite structure can be prepared by using nitrates at low temperatures below 220 °C. When the anhydrous ethanol is used as the solvent, CuInS2 film samples prepared with the sulfur powder as the sulfur source, the prepared CuInS2 film has a wurtzite structure with poor crystallinity. When the other solvents such as ethylenediamine and ethanolamine were used, the CuInS2 films prepared by using thiourea as the sulfur source also have the wurtzite structure. The product film with sulfur powder consists of a number of irregular particles with diameters between 0.3 and 0.5 μm, while the product films with thiourea consist of a number of flaky crystals and small spherical particles. The band gaps of the CuInS2 films were estimated by extrapolation method. The estimated band gap of the wurtzite CuInS2 film prepared by sulfur powder as sulfur source is about 1.45 eV, which is close to the theoretical value.