Cation Exchange-Assisted Hot Injection for PbSe Nanocrystalline Structures Anchored to Sb2S3: Constructing a Deeply Buried Back Interface for Highly Efficient Solar Cells

Severe back interface recombination still impedes the enhancement of device performance in Sb2S3 solar cells, primarily due to a plethora of defects derived from suspended bonds at the rear surface of Sb2S3. In contrast to the conventional physical absorption method (i.e., Sb2S3/Spiro-OMeTAD), herein, we develop a novel strategy involving cation exchange-assisted hot injection for the in situ anchoring of PbSe nanocrystalline structures to the surface of Sb2S3. This process successfully establishes a deeply buried back interface, thereby creating a robust chemically bonding bridge for facilitating smooth carrier transfer. Additionally, the energy level arrangement has been tailored by the quantum size effect of PbSe particles to mitigate band offsets at the back interface. Consequently, the decent PbSe substantially reduces the density of surface defects from 2.44 × 1016 to 9.8 × 1015 cm–3, leading to an effective suppression of nonradiative recombination as supported by the reduction in the surface photovoltage. Ultimately, the power conversion efficiency of Sb2S3 solar cells based on the ITO/TiO2/CdS/Sb2S3/PbSe/C/Ag architecture is elevated from 6.78 to 7.34%, representing the highest efficiency achieved for full-inorganic Sb2S3 solar cells to date. This construction tactic of the deeply buried back interface sheds light on the pursuit of highly efficient Sb2S3 solar cells.