Preparation of Monolithic Cu(In0.7Ga0.3)Se2 Nanopowders and Subsequent Fabrication of Sintered CIGS Films
- Preparation of Monolithic Cu(In0.7Ga0.3)Se2 Nanopowders and Subsequent Fabrication of Sintered CIGS Films
- 송봉근; 정재희; 배귀남; 박형호; 박종구; 조소혜
- Solar Cell; CIGS Compounds; CIGS Absorber Layer; Mechano-Chemical Process; Heat
Treatment; Monolithic; Particle Size Analysis
- Issue Date
- Journal of nanoscience and nanotechnology
- VOL 13, NO 9, 6042-6051
- Cu(In,Ga)Se2 (CIGS) is a compound semiconductor and is one of the most attractive light-absorbing
materials for use in thin film solar cells. Among the various approaches to prepare CIGS thin films,
the powder process offers an extremely simple and materials-efficient method. Here, we report the
mechano-chemical preparation of CIGS compound powders suitable for fabrication of CIGS films
by a powder process. We found that the CIGS phase was formed from the elemental powders of
Cu, In, and Se and liquid Ga using high energy milling process with a milling time as short as
40 min at 200 rpm due to a self-accelerating exothermic reaction. The morphology and size of the
CIGS powders changed with a function of the milling speed (100-300 rpm), leading to an optimal
condition of milling at 200 rpm for 120 min. We also found that it was difficult to obtain a monolithic
phase of the CIGS powders without severe particle aggregation by mechano-chemical milling alone.
Therefore, in combination with the milling, subsequent heat-treatment at 300 ℃ was performed,
which successfully provided monolithic CIGS nanopowders suitable for powder process. When a thin
film was fabricated from the monolithic CIGS nanopowders, a highly dense film with large crystalline
grains was obtained. The CIGS film preserved its chemical composition of CuIn0.7Ga0.3Se2 after
sintering as evidenced by Raman spectroscopy, EDS and SAED pattern of transmission electron
microscopy. The film was also found suitable for a light absorbing layer of CIGS solar cells with its
band gap energy of 1.14 eV evaluated by transmittance spectroscopy.
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