Inkjet printed CuIn(1-X)GaXSe2 thin film by controlled selenium distribution for improved power conversion efficiency in chalcopyrite solar cells

Abstract

Selenium (Se) vapor pressure is a key factor during the selenization of CuIn1-XGaX (CIG) film to obtain a high-quality CuIn1-XGaXSe2 (CIGS) absorber layer. To investigate the effect of Se vapor distribution on the grain growth of inkjet printed precursor film, two geometries of graphite box (square and circular) are used. The results revealed that selenization in the round graphite box give rise to uniform surface coverage and suppressed fine-grained layer due to adequate and uniform distribution of Se vapor. In contrast, film selenized in a square graphite box exhibits high strain and low crystallinity with a thick fine-grained layer. Probable Se vapor distribution inside the graphite box based on internal geometrical constraint and its impact on crystal phase and microstructure is discussed. Finally, CIGS devices fabricated using films selenized in a round graphite box demonstrates higher power-conversion efficiency of 5.2%, owing to high light absorption and efficient carrier separation. Based on J-V and EQE results, probable losses and recombination in the devices are examined and discussed.

Keywords

• CIGS
• Inkjet printing
• Se vapor
• Graphite box geometry
• Fine-grained layer