Solar cells based on Cu(In,Ga)Se₂ absorbers are the most efficient ones among all thin film photovoltaics. The current world record efficiency was attained by applying a rubidium fluoride (RbF) post deposition treatment (PDT) to the absorber. However, it is still not clear why the introduced Rb improves the solar cell performance. In order to investigate the beneficial effect of Rb, a Cu(In,Ga)Se₂ absorber was grown on a Mo coated alkali free substrate and subjected to a RbF PDT. This pure RbF PDT without any additional alkalis from the substrate leads to a strong increase in solar cell efficiency. A thin cross sectional lamella was cut out of the layer stack and investigated via a combination of electron microscopy and high resolution synchrotron based methods. This combinatory approach provides clear indications of the origin of the beneficial effect of Rb. It is evident that Rb agglomerates at detrimental random high angle grain boundaries and dislocation cores, where it likely passivates defects, which would otherwise lead to a recombination of carriers. In contrast, Rb does not agglomerate at benign Σ3 twin boundaries. Additionally, Rb segregates at the interface between the absorber and the MoSe₂ layer.

在所有薄膜光伏电池中，基于Cu（In，Ga）Se ₂吸收剂的太阳能电池是效率最高的太阳能电池。当前的世界纪录效率是通过对吸收器进行沉积后处理（PDT）的氟化tained（RbF）达到的。然而，仍不清楚为什么引入的Rb改善了太阳能电池的性能。为了研究Rb的有益作用，Cu（In，Ga）Se ₂吸收剂在涂有Mo的无碱基材上生长，并进行RbF PDT。这种纯RbF PDT，无需从基板上添加任何碱，可大大提高太阳能电池的效率。从层堆叠中切出薄的横截面薄片，并通过电子显微镜和基于高分辨率同步加速器的方法的组合进行研究。这种组合方法提供了Rb有益作用起源的明确指示。显然，Rb在有害的随机高角度晶粒边界和位错核心处聚集，在该处可能钝化缺陷，否则将导致载流子重组。相反，Rb不会在良性Σ3双晶界发生团聚。此外，Rb在吸收剂和MoSe ₂之间的界面处偏析 层。