Fabrication of Cu(In,Ga)(S,Se)2 Solar Cells by Solution Method
Cu(In,Ga)S2 (CIGS) nanoparticles were synthesized by hot-injection method at temperature of 240°C under nitrogen ambient, then dispersed in hexanethiol to form stable ink. CIGS thin films were prepared by doctor-blade method and annealed under different amounts of selenium at 540°C for 20 min. After annealing, the Cu(In,Ga)(S,Se)2 (CIGSSe) films showed increasing crystallinity, particle size, and Se concentration with increasing amount of selenium. In addition, only CIGSSe phase existed in the film after annealing. The properties of CIGSSe cells were improved with increasing amount of selenium. The optimal results were obtained for the sample prepared with 0.2 g Se, showing short-circuit photocurrent density (JSC) of 27.36 mA/cm2, open-circuit voltage (VOC) of 0.42 V, fill factor (FF) of 0.36, and conversion efficiency (η) of 4.2%. These results provide important insights into economically feasible production of CIGS-based solar cells.