Effects of Successive CdCl₂ Treatments on the Texture of Thin Film CdTe Solar Cells

Abstract

The CdCl2 activation treatment is required for high efficiency CdTe solar cells. The treatment has many effects including increasing grain size and randomizing texture. Increasing grain size should result in higher efficiencies by minimizing grain boundary recombination. The use of metaloxide layers to replace cadmium sulphide allows higher activation temperatures to be used resulting in larger grain sizes. However, use of these higher temperatures may affect the concentration of chlorine in the grain boundaries. Here we investigate the use of a first high temperature activation on closed space sublimated (CSS) Au/CdTe/TEC12D devices followed by a second optimized cadmium chloride treatment. We report on the effects on texture and grain size. Electron backscatter diffraction (EBSD) has been carried out using a Plasma Focused Ion Beam (PFIB) equipped with spin milling. Initial results indicate that the first higher temperature activation results in larger grains and a randomized texture.