Effect of Al content on the performance of Cu(In1−x Al x )S2 synthesized by hydrothermal solution processing

Abstract

Al doped CuInS2 (CIS) material was prepared by a low cost and non vacuum wet chemical process. The effect of aluminum concentrations on the crystal structure, morphology, percentage composition, and band gap of Cu(In1−xAlx)S2 were investigated. The X-ray diffraction (XRD) shows that the size of crystal grains decreased with the increase of Al concentrations. Scanning electron microscope presents the size of particles is gradually become smaller with Al concentrations increase. The reason for these phenomenons is Al concentrations cause the solution to a colloidal state. Binding between ions and grains growing together gradually become harder in a colloidal solution. In situ XRD tests show that CIS perform exceptional thermal stability below 798 K but decomposed to Cu2S and In2S3 at the temperature higher than 798 K. Results of energy dispersive X-ray analysis (EDAX) show the nearly stoichiometry composition of Cu(In1−xAlx)S2 which matched well with the ratio of the precursor solution. The transmission spectra show that spectral transmittance decrease with decreasing contents of Al. The band gap of Cu(In1−xAlx)S2 is continuously tuned in a range of 1.56–1.92 eV as Al/(Al + In) content ratio varied from 0 to 0.3. Finally, the mechanism of Al concentration on the properties of Cu(In1−xAlx)S2 was discussed briefly.