Mesoporous Au@Cu2-x S 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@Cu2-xS 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@Cu2-xS 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@Cu2-xS 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@Cu2-xS 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@Cu2-xS(20:10)-based PSCs achieves a champion efficiency over 22%, higher than that of the Au@Cu2-xS-based device.