Fabrication of a smooth, large-grained Cu(In,Ga)Se2 thin film using a Cu/(In,Ga)2Se3 stacked precursor at low temperature for CIGS solar cells

• Main Authors: Jung, Gwang Sun, Mun, Sun Hong, Shin, Donghyeop, Chalapathy, R. B. V, Ahn, Byung Tae, Kwon, Hyuksang
• Format: Journal Article
• Language: English
• Published: 02.01.2015
• ISSN: 2046-2069
• DOI: 10.1039/c4ra13954b

Cu(In,Ga)Se 2 (CIGS) thin films used for commercial CIGS solar cells were fabricated from Cu-Ga-In metal precursors; they contained large voids at the CIGS/Mo interface and their surface was rather rough due to large volume expansion. To solve these problems, we employed a Cu/(In,Ga) 2 Se 3 stacked precursor, in which the pre-existing Se could reduce the volume expansion during CIGS formation. With the pre-contained Se in the precursor, a uniform and void-free CIGS film with good adhesion was formed. SEM morphology revealed that a liquid phase was generated at 400 °C by the reaction of Cu and (In,Ga) 2 Se 3 under Se deficient conditions even though the melting point of Cu and (In,Ga) 2 Se 3 are much higher. A large-grained CIGS film can be formed as low as 450 °C with the help of liquid phase formation and we proposed the reaction mechanism. The film was applied to CIGS solar cells to achieve 13.5% efficiency without AR coating. Grain growth of CIGS thin film assisted by liquid CuIn from Cu/(In,Ga) 2 Se 3 stacked precursor.