Cu_2Sn_(1-x)Ge_xS_3 (CTGS) SOLAR CELLS: A PROMISING CANDIDATE FOR EARTH-ABUNDANT AND NONTOXIC THIN-FILM MULTI-JUNCTION SOLAR CELLS

摘要

We have fabricated Cu_2Sn_(1-x)Ge_xS_3 (CTGS) thin-film solar cells from Cu-Sn co-sputtered precursorsusing a newly developed sulfurization method with S and GeS_2 vapors. The conversion efficiency of the CTGS solarcells was significantly improved to be as high as 6.0% compared with the values of Cu_2SnS_3 solar cells. We foundthat mixture of S and GeS_2 vapors accelerated grain growth during the sulfurization process. The bandgap energy ofthe CTGS film was about 1.0 eV. CTGS is a promising candidate for bottom cells of double-junction solar cells.