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We demonstrate the deposition of ZnS thin films with a thickness of 0.04 to 0.45 µm at temperatures ranging from 25 to 80 • C from chemical baths comprising zinc sulphate, triethanolamine and thioacetamide at pH of about 10. The as-deposited films do not show crystallinity, are very resistive (conductivity 10 −9 −1 cm −1 ) and possess no photosensitivity. Annealing of the films in air at 450 to 500 • C for 1-2 h leads to partial conversion of the ZnS films to ZnO films. This is accompanied by an increase in the photoconductivity by more than six orders of magnitude. The optical bandgap is > 3.85 eV in the as-prepared films; after annealing in air the value drops to about 3.7 eV.

Chemical bath deposition techniques for bismuth suffide, bismuth selenide, antimony sulfide, and antimony selenide thin films ofabout 0.20-0.25 im thickness are reported. All these materials may be considered as solar absorber films: strong optical absorption edges, with absorption coefficient, a,> i04 cm', are located at 1 .3 1 eV for Bi2Se3, 1.33 eV for Bi2S3, 1 .8 eV for Sb2S3, and 1 .35 eV for Sb2Se3. As deposited, all the films are nearly amorphous. However, well defined crystaffine peaks matching bismuthinite (JCPDS 17-0320), paraguanajuatite (JCPDS 33-0214), and stibnite (JCPDS 6-0474) and antimony selenide (JCPDS 15-0861) for Bi2S3, Bi2Se3, SbS3 and Sb2Se3 respectively, are observed when the films are annealed in nitrogen at 300 °C. This is accompanied by a substantial modification ofthe electrical conductivity in the films: from iO cm' (in as prepared films) to 10 c -' cm' in the case of bismuth suffide and selenide films, and enhancement of photosensitivity in the case of antimony suffide films. The chemical deposition of a CuS/CuSe film on these V,-VI films and subsequent annealing at 300 °C for 1 h at 1 ton of nitrogen leads to the formation of p-type films (conductivity of 1-100 IT' cm') of multinary composition. Among these, the formation of Cu3BiS3 (JCPDS 9-0488) and Cu3SbS4 (JCPDS 35-0581), CuSbS2 (JCPDS 35-0413) have been clearly detected. Solar energy applications ofthese films are suggested. key words: photovoltaic materials, semiconductor thin films, chemical bath deposition

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