Chemically deposited antimony selenide thin films

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Chemically deposited antimony selenide thin films Y. Rodríguez-Lazcano, Y. Peña, M. T. S. Nair, and P. K. Nair Centro de Investigación en Energía, Universidad Nacional Autónoma de México Temixco, Morelos 62580, MÉXICO. [email protected]

ABSTRACT Chemical bath deposition of thin films of antimony selenide from aqueous solutions containing complexes of antimony with citrate, tartrate and thiosulfate as ligands and sodium selenosulfate as source of selenide is reported. The films obtained appear amorphous in the asprepared form and become crystalline upon annealing at 300oC. The X-ray Diffraction (XRD) patterns of the annealed films show peaks attributable to Sb2Se3 and Sb2O3. Electron microprobe analyses have shown that the atomic ratio of Se/Sb is less than 1.5 in these films. The films are photoconductive and exhibit a high resistivity in the dark. Both direct (1.4 eV) and indirect (1.31.5 eV) band gaps are observed for the films.

INTRODUCTION Antimony selenide (Sb2Se3) with an optical band gap of 1.11 eV [1] is considered appropriate for application as the absorber component in polycrystalline thin film solar cells. Methods reported for obtaining thin films containing the material include vacuum evaporation [2], spray pyrolysis [3], electrodeposition [4, 5] and chemical bath deposition [6,7]. Thin films obtained by chemical bath deposition are reported as amorphous, while those obtained by the other methods are crystalline. In some cases crystallinity is achieved only after the films have been annealed at temperatures up to 200oC. Chemical bath deposition has the advantage of being a low capital-intensive technology for obtaining thin films of metal chalcogenides over surfaces of large areas and of any shape. Hence the technique is widely accepted as suitable for depositing thin films for solar energy related applications [8]. The use of chemically deposited antimony selenide thin films as photoactive material in photoelectrochemical cells has been demonstrated [7]. In the present work, we deposited antimony selenide thin films from different chemical baths with a view to investigate the possibility of improving the crystallinity of the films by post deposition treatments and to analyze their electrical and optical properties.

EXPERIMENTAL DETAILS Deposition of thin films: Clean microscope glass slides were used as substrates for the deposition of antimony selenide thin films from three different baths prepared by using antimony trichloride or potassium antimony tartrate as described below: Bath # 1: One gram of antimony trichloride (SbCl3 -Fermont) was transferred to a 100 ml beaker. To this was added 37 ml of 1M solution of sodium citrate (Baker Analyzed Reagent), with stirring. Upon the addition of citrate, a white precipitate is formed initially, which dissolves

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