A non-toxic, solution-processed, earth abundant absorbing layer for thin-film solar cells

Copper zinc tin sulfide (Cu ₂ZnSnS ₄, CZTS) has attracted significant attention in the past few years as a next generation absorber material for the production of thin film solar cells on large scales due to the high natural abundance of all constituents, tunable direct band gap energy ranging from 1.0 to 1.5 eV, and large absorption coefficient. In addition, to address the issue of expensive vacuum-based processes, non-vacuum solution-based approaches are being developed for CZTS absorber layer deposition. Here, we demonstrate the fabrication of a high quality CZTS absorber layer with a thickness of 2.8-3.0 μm and micrometre-scaled grains (1-2.5 μm) using air-stable non-toxic solvent-based inks. Our approach for the fabrication of CZTS absorber, reported here, will be the first step in achieving low-cost and large area solar cells with high efficiency.