Mesoporous Au@Cu2−xS Core–Shell Nanoparticles with Double Localized Surface Plasmon Resonance and Ligand Modulation for Hole‐Selective Passivation in Perovskite Solar Cells

Core–shell nanomaterials have led to their fascinating properties in optical applications due to the localized surface plasmon resonance (LSPR). Herein, a mesoporous core–shell Au@Cu 2− x S nanomaterial with dual LSPR characteristics is introduced to stabilize and passivate the perovskite/spiro‐OMeTAD interface of perovskite solar cells (PSCs). Thanks to the LSPR, Au@Cu 2− x S nanoparticles (NPs) have the potential to enhance the infrared absorption and intensify the local electric field at the perovskite/spiro‐OMeTAD interface. The embedding of the mesoporous Au@Cu 2− x S in the spiro‐OMeTAD layer can improve the contact and form “bridges” between perovskite grains and spiro‐OMeTAD. With the help of cationic surfactant cetyltrimethylammonium bromide, these mesoporous Au@Cu 2− x S NPs can passivate surface traps and smooth the valence‐band offset at the perovskite/spiro‐OMeTAD interface for hole transferring. Furthermore, the improved hole mobility can offer balanced charge transport and prevent the carrier accumulation at interfaces. As a result, the Au@Cu 2− x S(20:10)‐based PSCs achieves a champion efficiency over 22%, higher than that of the Au@Cu 2− x S‐based device.