Synthesis of Cu-Sb-Bi Sulfide Nanocrystals for Solution-Processed Solar Cells

Abstract

P-type nanocrystals of copper-based chalcogenides such as CuInSe₂ and Cu₂ZnSnS₄ have attracted increasing attention in photovoltaics because of their prospects for cheap solution-processed solar cells. In this study, copper-antimony-sulfide (CAS) nanocrystals including CuSbS₂, Cu₃SbS₄ and Cu₁₂Sb₄S₁₃ were synthesized by a hot-injection method. The crystal phase control was achieved by changing the reaction temperature and starting precursor ratios. Crystal morphologies significantly depended on the crystal phase; CuSbS₂ and Cu₁₂Sb₄S₁₃ were rod-like crystals while Cu₃SbS₄ was angulate crystals. Photoemission yield measurements and UV-Vis-NIR spectroscopy revealed differences in the electronic structures of the three phases. Devices coupling CAS particulate films with dense CdS layers exhibited a diode like behavior, suggesting the formation of pn junction between them. Devices based on the structure of ITO/ZnO/CdS/CuSbS₂/Au exhibited a PV response with the power conversion efficiency of 0.01% under simulated sunlight, while devices with Cu₃SbS₄ and Cu₁₂Sb₄S₁₃ showed no PV response. Although the obtained efficiency is very low for practical applications, improving the film quality by sintering and optimizing the thickness would further improve the performance.