A novel thermal annealing process to improve Ga diffusion in CIGS thin film solar cells

CIGS thin film solar cells have attracted extensive attention due to their high conversion efficiency (the highest conversion efficiency of 23.35%). The electrodeposition method is widely used to prepare CIGS thin films because of its simple process, fast deposition rate, low equipment cost and high material utilization rate. However, the aggregation of Ga, poor crystallinity and the interface recombination led the poor conversion efficiency of 17.3%. In this work, pulsed optic-thermal coupling process was employed to improve the film quality and device performance. With the pulsed optic-thermal coupling process, the surface temperature of film could rise to 550 ℃ in few seconds, which suppressed the prefer reactions between In-Se and Ga-Se. Large-grained CIGS thin films were prepared with fine grains at the back contact eliminated, which improved the crystallinity. The performance of CIGS thin film solar cells was also improved with a conversion efficiency of 9.14% being obtained with the optimized pulsed optic-thermal coupling process.