Copper-Based Semiconductor Nanocrystal Hole-Transport Layers Enable Efficient and Stable Sb₂S₃ Solar Cells

High-efficiency antimony sulfide (Sb₂S₃) solar cells have successfully learned from the device structure of perovskite solar cells and often use spiro-OMeTAD as the hole-transporting layer (HTL). However, the stability of spiro-OMeTAD under an atmospheric environment is poor. It is generally believed that copper-based semiconductor nanocrystals (NCs), demonstrating appropriate valence band maximum (VBM), remarkable stability, and abundant elements, are suitable for the HTLs. In practice, however, related research has mainly focused on perovskite solar cells. In this work, Cu₂SnS₃, Cu₂ZnSnS₄, and CuInS₂ nanocrystals are synthesized by the hot injection method and successfully used as HTLs in high-efficiency Sb₂S₃ solar cells. Through hexanethiol ligand exchange, dense and continuous copper-based semiconductor nanocrystal films are prepared by the spin coating method. Furthermore, the device performances of Sb₂S₃ solar cells based on Cu₂SnS₃, Cu₂ZnSnS₄, and CuInS₂ HTLs are up to 6.52, 6.70, and 7.06%, respectively. It shows a comparable performance with the traditional spiro-OMeTAD (7.10%) and significantly improved stability compared to the Sb₂S₃ solar cell based on the spiro-OMeTAD HTL in an air atmosphere. This work highlights the importance of HTL in achieving high-efficiency and stable Sb₂S₃ optoelectronic devices.