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

We report on the development of copper zinc tin chalcogenide compounds, especially kesterite Cu2ZnSn S,Se 4 CZTSSe that can be used for low cost solar cells using scalable inexpensive coating processes. For the formulation of copper zinc tin sulfur inks we developed a new method relying on binary and ternary chalcogenide nanoparticles as precursors. The chemical composition of the resulting absorber layers can be controlled by varying the ratio of the NP precursors in the ink. The ink was first coated at room temperature on Mo coated soda lime glass substrates. After soft heat treatment in air, the obtained precursor layers were subjected to further annealing process under Ar H2S or Ar Se atmosphere to allow solid state reaction of the precursors to form CZTS Se absorber layers. The morphology and phase formation were investigated with scanning electron microscopy and grazing incident X ray diffraction. The Raman spectroscopy was utilized to better identify all secondary phases. Solar cell formation is completed by chemical bath deposition of CdS buffer layer followed by sputtered i ZnO ZnO Al bi layers. Solar cells with efficiencies around 1.17 were achieve