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11 September 2007 Fabrication of Cu(In,Al)Se2 solar cells by three-stage evaporation process
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Abstract
Cu(In,Ga)Se2 (CIGS) solar cells are leading candidates for low-cost and high-efficiency solar cells. A band gap energy (Eg) of CIGS can be controlled from 1.0 eV (CuInSe2) to 1.7 eV (CuGaSe2). The Eg of CIGS can be adjusted to the theoretically estimated optimum value of 1.4 eV. However, maximum efficiencies for CIGS solar cells were achieved at Eg=1.1~1.2 eV. A higher-Ga addition degrades the electronic properties of CIGS films. Compared to CIGS, Cu(In,Al)Se2 (CIAS) can be adjusted the same Eg by a small Al addition. We report on the fabrication of the CIAS film on Mo/soda-lime glass (SLG) substrate by a three-stage evaporation process. The film composition was Cu/(In+Al)=0.89, Se/Metal=0.99 and Al/(In+Al)=0.15. The Eg of the film was 1.15 eV from the quantum efficiency measurement. The cross-sectional scanning electron microscope image of the film showed a grain size of approximately 1μm. The composition depth profile by secondary ion mass spectroscopy showed the V-shape distribution of Al in the depth direction. The CIAS solar cell consisted of Al/ITO/ZnO/CdS/CIAS/Mo/SLG was fabricated. The active cell area was 0.12 cm2. A current-voltage measurement under illumination (AM1.5, 100mW/cm2) at 25°C showed the area efficiency of 13.1% without antireflection coating.
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Takao Hayashi, Takashi Minemoto, Tsutomu Araki, and Hideyuki Takakura "Fabrication of Cu(In,Al)Se2 solar cells by three-stage evaporation process", Proc. SPIE 6651, Photovoltaic Cell and Module Technologies, 66510L (11 September 2007); https://doi.org/10.1117/12.731718
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