Preparation and Characterization of Copper Gallium Diselenide Used as the Absorber in thin-film Solar Cells
Date Issued
2010
Date
2010
Author(s)
Liu, Zhi-Liang
Abstract
Copper gallium diselenide (CuGaSe2) powders were synthesized via the sol-gel method followed by a selenization process. The sol-gel process can effectively reduce the required synthesis temperature to 400oC due to enhanced reactivity and improved composition homogeneity. The amount of the impurity phase Cu2Se was decreased when sufficient Ga3+ was added during the reactions. CuGaSe2 powders were successfully prepared when the Ga3+/Cu2+ molar ratio was increased to 2. The formation of CuGaSe2 with a pure chalcopyrite structure was confirmed via Rietveld refinement results. With decreasing the Ga3+/Cu2+ molar ratios, the particle size of the prepared CuGaSe2 powders was significant enlarged because of the copper selenide phases act as the flux for the particle growth. The optical absorption spectra reveal that the band gap of obtained CuGaSe2 is 1.68 eV. The sol-gel method combine with the selenization process was demonstrated to provide a potential approach to fabricate CuGaSe2 materials.
A simple process for preparing CuGaSe2 (CGS) absorber layers was developed in this study. The sol-gel derived CGS precursor pastes were coated via a doctor blade technique followed by the selenization process. On selenization at 450oC single-phased CGS thin-films were obtained. The Raman analysis confirmed that the obtained CuGaSe2 thin films belonged to chalcopyrite structure. The amounts of Cu2Se particles on the surface of the film were reduced when the Ga3+/Cu2+ molar ratio was increased. The uniform film was obtained at the Ga3+/Cu2+ molar ratio of 1.5. The GIXD analysis reveals that the CuGaSe2 phase distributes through the whole film. Because the existence of the highly conductive Cu2Se, the resistivity of obtained CuGaSe2 films were raised with increasing the molar ratio of Ga3+ to Ga2+. The formation mechanism of CuGaSe2 thin films is proposed. The copper selenide phases formed at first and then these phases lead the formation reaction of CuGaSe2.
Subjects
CuGaSe2
sol-gel
chalcopyrite
Type
thesis
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