Hydrothermal Synthesis And Characterization Of Solar Materials Cu₂ZnSnS₄ Nanocrystallines

Cu2ZnSnS4 (CZTS) is an ideal candidate absorber material for thin film solar cells with an optimal band-gap for a single junction photovoltaic device of 1.4-1.5 eV, high absorption coefficient (>104cm-1), and abundant elemental components. In the past 20 years, various method such as sol-gel, sputtering deposition, spray pyrolysis, co-evaporation, soft chemistry method were utilized to deposit CZTS layer. It is worth noting that the efficiency of CZTS based solar cells has increased from 0.66% in 1996 to 9.6% in 2010.In this thesis, we aim to further enrich and develop the hydrothermal synthesis route, and apply it to prepare Cu2ZnSnS4 nanocrystallines. We expect that a relatively universal synthetic route is developed. At the same time, we characterize the as-prepared product. The details are as follows:1. Synthesis of Cu2ZnSnS4 nanocrystallines. Cu2ZnSnS4 nanocrystallines have been successfully synthesized by a hydrothermal method using CuCl, ZnCl2, SnCl4·5H2O and (NH2)2CS as reaction reagents at 200℃. The effect of the reaction temperature and time on the formation of the Cu2ZnSnS4 nanocrystallines was discussed..2. Characterization of Cu2ZnSnS4 nanocrstallines. The as-grown product was characterized by X-ray powder diffraction, transmission electron microscopy, high-resolution transmission electron microscopy and selected-area electron diffraction. The results confirm that the product was polycrystalline Cu2ZnSnS4 nanoparticles with the diameter of 5-7 nm.3. The optical properties of Cu2ZnSnS4 nano-crystallines. The band-gap of Cu2ZnSnS4 nanocrystallines was estimated to be 1.70 eV via ultraviolet-visible (UV-vis) absorption spectrum of Cu2ZnSnS4 nanocrystallines. Raman spectrum of nanocrystallines had about 8 cm-1 red-shift in comparison with that of the responding bulk counterpart.4 Finally, we demonstrate the implementation of screen printing method in fabrication of CZTS thin films using the prepared CZTS.