Solution-Based Preparation of Cu2ZnSn(S,Se)4 for Solar Cells-Comparison of SnSe2 and Elemental Se as Chalcogen Source

Thin-film solar cells with a Cu2ZnSn(S,Se)(4) absorber were prepared in a two-step process based on a metal salt solution that is deposited onto a molybdenum-coated substrate and subsequently annealed in a selenium-containing nitrogen atmosphere. The solar cell performance could be improved to efficiencies above 10% without usage of the highly toxic hydrazine or H2Se gas. A crucial step for obtaining high-quality absorbers is the incorporation of Se during the annealing process. Therefore, a detailed investigation of elemental Se and SnSe2 as chalcogen sources with various process parameters was performed. SnSe2 resulted in absorbers with improved morphology but could achieve only medium efficiencies, whereas elemental Se forms a triple-layer structure with efficiencies of up to 10.3%.