| CuInS2 is the direct band gap semiconductor material and has a high optical absorption coefficient. CuInS2 is not sensitive to temperature. The band gap is 1.50 eV, which is close to the optimum band gap (1.45 eV). Therefore, CuInS2-based chalcopyrite materials are one of the most promising absorber materials for solar cells.CuInS2 thin films were prepared by paste coating in this paper. The precursors were prepared by using two methods. The Copper-Indium alloy, S powders and CuS, In2S3 as the starting materials were milled to prepare CuInS2 precursors. The paste then was coated on glass substrate as formation of the precusors; afterwards, the precursors were heat treated in the N2 atmosphere. Ultimately, the thin films with pure the CuInS2 phase and stoichiometric were successfully prepared by paste coating.The Copper-Indium alloys were prepared by induction smelting. The characterizations indicate that composition segregation occurs during nonequilibrium solidification of Copper-Indium alloys. Copper-Indium alloys prepared by induction smelting have been determined to be the mixtures of Cu11In9 phase and the Indium-rich phase. The Cu-In alloy and S powders were milled for 24 hours. The molar ratio of Cu,In and S in the solution was kept as 1:1.2:3. CuS and In2S3 were also milled for 24 hours. The molar ratio of Cu and In in the solution were kept as 1: 1 and 1.2:1. The grain size of precursors were about 1μm. CuInS2 thin films with stoichiometric can be obtained after sintering.This paper also studies the thermodynamics in sintering process of CuInS2 thin films. The results show that the chalcopyrite CuInS2 are formed even at 200℃. The CuInS2 films which have good crystallinity and chalcopyrite were obtained in sintering temperature of 400℃～450℃. The experiments revealed that the absorption coefficient of CuInS2 is greater than 1x105cm-1. The optical band gap of the films was between 1.5eV and 1.7eV. It is suitable for solar cells absorption layer.
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