Selenium passivates grain boundaries in alloyed CdTe solar cells

Cadmium telluride (CdTe) solar cells have achieved efficiencies of over 22%, despite having absorber layer grain sizes less than 10 ?m and hence a very high density boundaries. Recent research has shown that this is possible because partial passivation boundaries during the widely used cadmium chloride treatment, interior defects by selenium alloying CdTe. Here, state-of-the art TEM-based cathodoluminescence imaging to show that, in addition interiors, also passivates alloyed Cd(Sex,Te1-x) material (CST). Specifically, we find recombination at CST up an order magnitude lower CdTe This further explains superior performance graded devices provides potential new routes for efficiency improvement electricity cost reduction.