[13p-B9-1~11] New characterization technologies for functional properties of multinary compounds - new insight into development of multinary compound devices -

▲ [13p-B9-3] Effect of Post-deposition Se-annealing on the defect distribution in CuGaSe₂ Thin-films and Solar-cells

〇Muhammad Monirul Islam¹, Akira Uedono¹, Takeaki Sakurai¹, Christoph Hugenschmidt², Werner Egger³, Roland Scheer⁴, Ayham Dalla⁴, Reinhard Krause-Rehberg⁴, Katsuhiro Akimoto¹ (1.Tsukuba Univ., 2.Tech. Univ. Munchen, 3.Univ. Bundeswehr Munchen, 4.Martin Luther Univ. Halle)

Keywords:CuGaSe2, Se-annealing, photovoltaic

Chalcopyrite Cu(In,Ga)Se₂ (CIGS) being a pseudo-binary alloy of ternary CuInSe₂ and CuGaSe₂ is one of the most promising materials to realize high-efficiency thin-film solar cell. Band-gap of the CuGaSe₂ is 1.68 eV which is close to the ideal band-gap (1.4 eV under AM 1.5 sunlight) of the absorber-layer to achieve the highest possible efficiency. Moreover, larger band-gap makes the CuGaSe₂ suitable for the top-cell in the tandem structure together with CuInSe₂ as the bottom-cell. Nevertheless, so far, CuGaSe₂ solar cells with a CdS buffer have achieved efficiency of around 11 % for the thin film. Therefore, to achieve the optimized material quality of the CuGaSe₂ material which is compatible for highest possible efficiency, an extensive study of this material with various compositions is indispensable. In this paper, we have changed the post-deposition Se-annealing time to study the effect of Se-annealing on the properties of CuGaSe₂. Se-annealing was found to affect both the surface and also bulk of the film by controlling the defect-distribution along the depth of the film. Mechanism of the defect distribution has been investigated. Performance of the fabricated solar cells has been studied in correlation to the Se-annealing time.