Syntheses Of Multi-element Metal-sulfide Nanocrystals And Light To Current Conversion Properties Of Corresponding Ink Coated Thin Films

Utilization of solar energy for photovoltaic is an effective approach to deal with the energy crisis and environmental problem. Among a variety of different photovoltaic materials, multielement metal-sulfide thin film solar cell has attracted great deal of attention owing to their high light-to-electricity conversion efficiency and good stability. Utilizing nanocrystal-ink coating approach to fabricate thin film solar cell is promising owing to the merits of well-controled composition distribution, good scalability, non-vaccum and low cost.In this dissertation, four kinds of earth-abundant environmental benign multielement metal-sulfide nanocrystals have been synthesized using hot-injection method. Their properties of photo to electron conversion have been investigated. The major research works are concluded as follows:(1) Well-dispersed Cu3BiS3nanocrystals with sizes of8-11nm have been synthesized. According to characterization of the products at differenct reaction time, reaction intermediates (CuS2and Bi2S3) have been confirmed. Light absorption test shows that the band gap of Cu3BiS3nanocrystals is1.55eV. Photoelectroconduction test demonstrates the light and dark current density ratio is1.9, suggesting Cu3BiS3films processes good potential in the application of solar cell(2) Cuboid CuSbS2nanocrystals have been synthesized. The coated film based on CuSbS2nanocrystal-ink demonstrates a light absorption coefficient of higher than104cm-1in the visible region and a band gap of1.41eV. Photoelectrochemical characterization indicates that CuSbS2thin film electrode owns stable near0.1mA/cm2photogenerated current density and the electrode illustrates an Incident light to current efficiency (IPCE) of5%-15%in the visible region. These results reveal the promising prospects of using CuSbS2nanocrystal coating films in the field of solar energy conversion (e.g. solar cell and photoelectrochemical cell.etc).(3) Quaternary Cu2FeSnS4nanocrystals with sizes of10-14nm have been synthesized. The formation pathway from binary copper sulfide to ternary copper iron sulfide then to quaternary Cu2FeSnS4is illuminated by characterizing the products at different reaction time. Light absorption test shows that the band gap of Cu2FeSnS4nanocrystals is1.28eV. Thin film electrode prepared by Cu2FeSnS4crystal coating method demonstrates a noteable and stable photogenerated current density. These results show that Cu2FeSnS4can be applied to solar cell as the light-absorbing layer.(4) The techniques of synthsizing CZTS nanocrystals, nanocrystal-ink coating and corresponding thin film soalr cell fabrication have been developed. CZTS solar cell with structure of Mo/CZTS/CdS/i-ZnO/ZAO/Ag fabricated by nanocrystal ink coating method achieved the conversion efficiency of2.29%. The mechanism of lose of efficiency is also discussed preliminarily.