Application of grain boundary function to develop new materials for solar cells with high performance

本工作的动机是研究适合于提高微晶CdTe太阳能电池转换效率的晶界函数的起源，从而获得用于开发高性能太阳能电池新材料的晶界设计原理。我们发现与晶界相关的势垒不仅取决于晶界特性，还取决于其晶体结构引起的晶界极性。此外，CdCl2处理增加了晶界势垒，提高了CdTe太阳能电池的转换效率。这些发现表明，CdTe的晶界可以作为光生空穴-电子对分离的内置电位，而CdCl2处理后Cl向晶界的偏析会导致内置电位的作用增强，而不是导致带隙缺陷态的钝化。

The motivation of this work was to study the origin of grain boundary function suitable for achieving enhanced conversion efficiency of microcrystalline CdTe solar cells, and then to obtain a principle of grain boundary design for development of new materials for solar cells with high performance. We have found the potential barrier associated with grain boundaries in CdTe depends not only on grain boundary character but also on polarity at grain boundaries arising from its crystal structure. In addition, the CdCl2 treatment, which increases the conversion efficiency of CdTe solar cells, was found to increase the grain boundary potential barrier. These findings show that grain boundaries in CdTe can act as the built-in potential for separation of photogenerated hole - electron pairs, and that Cl segregation to grain boundaries after the CdCl2 treatment would result in the enhancement of the role of the built-in potential rather than the passivation of defect states in the band-gap.