溅射后硒化法制备的CIGS薄膜中Ga元素扩散研究

Gallium diffusion in CIGS thin films prepared by sequential sputtering/selenization technique

溅射后硒化制备Cu(In,Ga)Se2吸收层工艺过程中,Ga元素在吸收层底部富集现象是较为普遍的.本文从预制层工艺和硒化工艺两个方面研究了Ga元素在Cu(In,Ga)Se2吸收层中扩散的影响因素.结果表明,预制层中的Cu/(In+Ga)和硒化温度对Ga元素扩散的影响较为显著,而预制层中的Ga/(In+Ga)对Ga元素扩散的影响较小,Ga元素的扩散系数制约了其在Cu(In,Ga)Se2吸收层表面的含量.通过工艺优化提高吸收层表面的Ga含量,制备获得了光电转换效率为12.42%的Cu(In,Ga)Se2薄膜太阳能电池.

In the sequential sputtering/selenization process, Ga segregation at the back of Cu（In, Ga）Se2 （CIGS） absorber is frequently observed. In this paper, Ga diffusion in CIGS absorber is investigated during the sputtering and selenization process. Results show that Ga diffusion is closely related to Cu/（In＋Ga） ratio in the metallic precursors and the selenization temperature, but barely influenced by Ga/（In＋Ga） ratio in the metallic precursors. Based on Fick＇s second law, a simplified model is established to describe Ga diffusion from the back to the surface of CIGS absorber, which suggests that Ga diffusion coefficient is the dominant factor to constrain Ga content near the absorber surface. By process optimization, Ga/（In＋Ga） ratio near the absorber surface is successfully increased. Accordingly, a CIGS solar cell device with efficiency of 12.42% has been obtained.