The p-type nanocrystals (NCs) of copper-based chalcogenides, such as CuInSe2 and Cu2ZnSnS4, have attracted increasing attention in photovoltaic applications due to their potential to produce cheap solution-processed solar cells. Herein, we report the synthesis of copper-antimony-sulfide (CAS) NCs with different crystal phases including CuSbS2, Cu3SbS4, and Cu12Sb4S13. In addition, their morphology, crystal phase, and optical properties were characterized using transmission electron microscopy, X-ray diffractometry, UV-vis-near-IR spectroscopy, and photoemission yield spectroscopy. The morphology, crystal phase, and electronic structure were significantly dependent on the chemical composition in the CAS system. Devices were fabricated using particulate films consisting of CAS NCs prepared by spin coating without a high-temperature treatment. The CAS NC-based devices exhibited a diode-like current-voltage characteristic when coupled with an n-type CdS layer. In particular, the CuSbS2 NC devices exhibited photovoltaic responses under simulated sunlight, demonstrating its applicability for use in solution-processed solar cells.

Solution-processed photovoltaic (PV) devices based on semiconductor nanocrystals (NCs) such as Cu 2 ZnSnS 4 (CZTS) and CuInS 2 (CIS) are attracting much attention for use in next-generation solar cells. However, the performance of NCbased devices is hindered by insulating surface-capping ligands that limit transfer/transport of charged carriers. Here, to remove surface-capping ligands (long-chain fatty amines) from NCs, we use the strong alkylating agent methyl iodide, which converts primary amines to quaternary amines that have low coordinating affinity to the NC surface. X-ray diffraction, Raman spectroscopy, and Fourier transform infrared spectroscopy analyses confirm the successful removal of capping ligands from the CZTS surface after treatment with methyl iodide without changing the crystal structure of CZTS. CZTS and CIS NC-based devices treated with methyl iodide exhibit a reproducible PV response under simulated sunlight. The developed route can potentially enhance the performance of NC-based devices used in a broad range of applications.

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ZnO nanocrystals (NCs) were synthesized by heating Zn (II) acetylacetonate in oleic acid/oleylamine in the presence of 1,2-hexadecanediol at 220 • C. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) measurements revealed the formation of monodispersed ZnO NCs of ca. 7 nm. ZnO NC assembled films were fabricated on a glass substrate by deposition with the colloidal ZnO NCs dispersed in toluene. The film composed of the NCs showed good optical transparency in the visible to near-infrared region. A device coupling the ZnO NC film with a p-type Cu 2 ZnSnS 4 (CZTS) NC film exhibited an obvious diode-like current-voltage behavior. The results suggest that the transparent ZnO film has a potentiality to be used for an n-type window layer in some optoelectronic applications.