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.

无需额外硒化的四元溅射法，是制备光伏用铜铟镓硒（Cu(InGa)Se2，CIGS）薄膜的低成本替代方案。然而，未经硒化处理的器件效率远低于经硒化处理的器件。为阐明这一问题，我们全面对比了吸收层的多项性能，包括形貌、深度分布、组分、电学特性以及复合机制。结果表明，在无硒气氛下退火的CIGS薄膜表面硒含量低于含硒气氛下退火的样品；硒元素的流失降低了薄膜的载流子浓度，同时提升了其电阻率。此外，硒元素的流失使得主导复合机制转变为CIGS/硫化镉（CdS）界面复合。界面复合的加剧被认为是无硒气氛退火器件效率降低的原因。