Application of Zn-Compound Buffer Layer for Polycrystalline CuInSe2-Based Thin-Film Solar Cells

Abstract

In order to meet the requirement for the development of a more environment-friendly device structure for polycrystalline CuInSe2-based thin-film solar cells, Zn compound buffer layers for use as an alternative to CdS buffer layers have been fabricated by a chemical-bath deposition (CBD) method which is believed to be cost-effective and applicable to large-area deposition. CIS-based thin-film solar cells with a Zn(O, OH)x buffer layer showed a relatively low efficiency of about 10% because of the difficulty in the reduction of the amount of OH- ions in the buffer layer. By adding a sulfur source to the CBD solution as a new approach to reduce the amount of OH- ions, a dramatic decrease in the content of hydroxide in the buffer layer and the formation of a better heterointerface between the CIS-based thin-film absorber and the ZnO window layer were achieved simultaneously for the first time. The application of Zn(O, S, OH)x as a buffer layer to CIS-based thin-film solar cells led to the higher efficiency of 12.8% on the active area of 3.2 cm2. Zn(O, S, OH)x fabricated by a CBD method was demonstrated to be a promising alternative to CdS and a more environment-friendly buffer layer, although further investigation is required to understand the mechanisms of the irradiation effect.