Oxidation effect on densification of CuInS2 absorber layer by paste coating

Copper indium disulfide (CuInS2) absorber layers were prepared by using a paste coating method. CuInS2 and CuS were chosen as precursor powders. Ethylcellulose and phosphate ester were used respectively as a resin and a dispersant. Dihydroterpineol was used as a solvent. The paste was distributed on an Mo-coated soda–lime glass substrate by screen-printing method. It was difficult to obtain the densification of the CuS-doped CuInS2 layer with only sulfurization in a graphite container box. However, when an oxidation process was applied to the CuS-doped CuInS2 layer before the sulfurization process, quite dense CuInS2 layers were obtained. Even though the chalcopyrite phase was nearly broke down with the oxidation, the phase was restructured with the sulfurization.