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Solution growth of CdS layers was investigated for use as heterojunction partner in CuInSe, and CdTe polycrystallinethin-film solar cells. Morphological and optical properties improved significantly when buffer solution was used. Cadmium acetate was found to be preferable as cadmium ion source as compared to cadmium chloride. Optimum conditions for slow ion-by-ion growth on Sn0,:F coated glass substrates of conformal CdS 500-2600 A thick layers with direct bandgap of -2.40 eV were cadmium salt concentration Q in the range 0.001-0.003 M, tluourea concentration 5 x Q, buffer solution concentration 20 x Q, pH in the range of 9.0-9.5, deposition temperature of 80-85" C and deposition time of 13-30 min. Heterogeneous growth on the substrate was found to depend critically on the availability of nucleation sites.