直拉单晶硅太阳电池中硼-氧复合体的形成机理及调控机制研究

Czochralski (CZ) silicon crystal is the basic material for the fabrication of high efficiency solar cells. However, the formation of boron and oxygen (B-O) complexes with electrical activity in CZ silicon under sunlight illumination can cause the degradation of solar cell efficiency (LID), which severely reduce the power output of solar cells. In this project, we will focus on the formation and control mechanisms of B-O complexes in CZ silicon. By investigating the basic properties of B-O complexes and related impactors, the physical picture of B-O complex will be understood. By studying the roles of oxygen dimer in the formation of B-O complexes, the microstructure model and formation mechanism of B-O complexes in CZ silicon will be illustrated. Meanwhile, we will try various annealing treatments and impurity co-doping technology to control the formation of B-O complexes in CZ silicon and then illuminate the related mechanisms. On this basis, we will combine the cell process optimization and the post-treatments to control the generation of B-O complexes during the fabrication of CZ silicon solar cells, which are of significance for the reduction and elimination of LID effect of CZ solar cells. These results will not only enrich the defect theory of B-O complexes in CZ silicon, but also be practically of interest for the resolution of LID effect of solar cells.

直拉单晶硅是制备高效太阳电池的基础材料，然而在光照条件下直拉单晶硅中硼和氧将结合形成电活性的复合体，导致太阳电池效率发生衰减，严重降低了其发电量。本项目将围绕直拉单晶硅中硼-氧复合体的形成机理和调控机制这一核心科学问题开展研究。通过系统研究直拉单晶硅中硼-氧复合体生成的基本性质及其影响因素，掌握硼-氧复合体生成的物理图像，重点关注硼-氧复合体与双氧之间的关系，进而阐明硼-氧复合体的微观结构模型及形成机理。并且，采用对直拉单晶硅进行退火处理及杂质共掺的策略对硼-氧复合体的生成进行合理调控，并阐明相关机制。在此基础上，综合各种有利因素，采用工艺优化及后处理等手段控制直拉单晶硅太阳电池制备过程中硼-氧复合体的生成，希望达到降低甚至消除太阳电池光衰减效应的目的。研究结果不仅能加深人们对直拉单晶硅中硼-氧复合体缺陷的理论认识，而且对解决其太阳电池光衰减效应具有重要的实际意义。

项目通过设计不同的材料体系，包括掺铝直拉硅单晶、低氧的铸造单晶硅、共掺碳/锗/锡单晶硅，研究了硼、氧和点缺陷的关系，在此基础上阐明了硅中硼-氧复合体生成的基本性质及其影响因素，掌握了硼-氧复合体生成的物理图像。并且研究了电池工艺（磷扩散吸杂、表面钝化等）和结构缺陷对硼-氧复合体的影响规律。明确了双氧是硼-氧复合体的组成部分，建立了硼-氧复合体的微观结构模型，获得了其形成机理。并且，采用对直拉单晶硅进行退火处理及杂质共掺的策略对硼-氧复合体的生成进行合理调控。相关结果共发表SCI论文11篇，申请国家发明专利4项。而且，研究结果作为重要组成部分获得了2019年国家技术发明二等奖。研究结果不仅能加深人们对直拉单晶硅中硼氧复合体缺陷的理论认识，而且对解决其太阳电池光衰减效应具有重要的实际意义。