Influence of annealing atmosphere on performances of CIGS film by sputtering from quaternary targets

Quaternary sputtering without additional selenization is a low-cost alternative method for the preparation of Cu(InGa)Se2 (CIGS) thin film for photovoltaics. However, the device efficiency without selenization is much lower than that with selenization. To illuminate the issue, we compared the properties of absorbers including the morphology, depth profile, composition, electrical properties and the recombination mechanism comprehensively. The results revealed that the superficial Se of CIGS film annealed in Se-free atmosphere is less than that annealed in Se-containing atmosphere,and the loss of Se reduced the carrier concentration and enhanced the resistivity of CIGS film. Besides, the loss of Se caused the dominant recombination mechanism to be CIGS/CdS interface recombination. The increase of interface recombination was considered to be the reason for the reduced efficiency of the device annealed in Se-free atmosphere.