A thin layer of CdS of about 200 Å enhances the solar conversion efficiency of CdS/CdTe solar cells from 8%
to 15%. A similar enhancement of the efficiency is observed on other solar cells, based on CuInSe2 or similar
compounds. The reason for this efficiency enhancement that is typical for CdS, but not observed with
similar semiconductors, is briefly described. The technical and economical importance of these solar cells
on the energy conversion market is summarized.