New formulation of Copper Zinc Tin Sulfide compounds: An Ink precursors route to printed photovoltaics

摘要

We report on the development of copper-zinc-tin-chalcogenide compounds, especially kesterite Cu_2ZnSn(S,Se)_4(CZTSSe) that can be used for low-cost solar cells using scalable inexpensive coating processes. For the formulation ofcopper-zinc-tin-sulfur inks we developed a new method relying on binary and ternary chalcogenide nanoparticles asprecursors. The chemical composition of the resulting absorber layers can be controlled by varying the ratio of the NPprecursors in the ink. The ink was first coated at room temperature on Mo coated soda lime glass substrates. After softheat treatment in air, the obtained precursor layers were subjected to further annealing process under Ar/H2S/ or Ar/Seatmosphere to allow solid state reaction of the precursors to form CZTS(Se) absorber layers. The morphology and phaseformation were investigated with scanning electron microscopy and grazing incident X-ray diffraction. The Ramanspectroscopy was utilized to better identify all secondary phases. Solar cell formation is completed by chemical bathdeposition of CdS buffer layer followed by sputtered i-ZnO/ZnO: Al bi-layers. Solar cells with efficiencies around 1.17% were achieved.