Survey of development of CZTS-based thin film solar cells

In 1988, K. Ito and T. Nakazawa of Shinshu University succeeded in fabrication of Cu₂ZnSnS₄ (CZTS) thin films by an atom beam sputtering method and confirmed that CZTS has suitable optical properties for thin film solar cells. In 1995, we began to develop the novel thin film solar cells using CZTS as an absorber to be able to use in the after next generation. The conversion efficiency of CZTS thin film solar cells reported for the first time in 1996 was only 0.66% and it have been improved to 6.77% in these twelve years at our laboratory. Quite recently, IBM using CZTSSe that contain Se to some extent achieved the conversion efficiency of over 10%. Because the potential of CZTS-based thin film solar cells seems to be quite high, we will be able to overcome the resource problem of rare-metal in the near future. In this talk we will survey our previous works and show the recent results concerning with this promising solar cells.