Novel non-hydrazine solution processing of earth-abundant Cu2ZnSn(S,Se)4 absorbers for thin-film solar cells

A novel non-hydrazine precursor solution followed by dip-coating has been developed to produce Cu2ZnSnS4 (CZTS) and Cu2ZnSn(S,Se)4 (CZTSSe) thin films. The precursor solution is based on an ethanol solution of metal–thioacetamide (TAA) complex with monoethanolamine (MEA) as the additive agent. By forming coordination complexes with TAA, metal cations are found to have good solubility in ethanol–MEA solvents, producing molecular-level blending in metal precursor solutions. All the materials are low-cost and environmentally friendly. The annealing treatments are conducted under vacuum and Se vapor to form CZTS and CZTSSe absorber films. A solar cell fabricated with the CZTSSe thin film exhibits power conversion efficiency of 5.36%, which is much higher than that (2.86%) of the cell using the CZTS thin film as absorber.