Surface-Plasmonic-Coupled Photodetector Based on MAPbI₃ Perovskites with Au Nanoparticles: Significantly Enhanced Photoluminescence and Photodetectivity

Organic-inorganic metal halide perovskites (OMHPs) are promising active materials suitable for highly efficient solar cells, photodetectors, light-emitting diodes, and sensors. In this study, methylammonium lead iodide (MAPbI3) thin sheets (TSs) were synthesized as OMHPs using both hybrid vapor-solution method for optical study and anti-solvent solution method for the photodetector. pi-Conjugated polyelectrolyte (pi- CPE), such as poly(9,9-bis(4 '-sulfonatobutyl)fluorene-alt-1,4-phe-nylene) potassium (FPS-K), was spin-coated on the MAPbI3 TS, and functionalized gold nanoparticles (Au-NPs) were hybridized. The laser confocal microscope photoluminescence (PL) intensity of the MAPbI3 TS was significantly enhanced after hybridization with Au-NPs/FPS-K, owing to the passivating effect of the FPS-K and the generation of extra-photoexcited charges by local surface plasmon resonance (LSPR) coupling with Au-NPs. These results were supported by the variation in the exciton lifetime measured from the time-resolved PL decay curves. The photocurrent of the MAPbI3 photodetector increased up to 1.1 x 104 times, and the photoresponsivity (R) and photodetectivity (D*) increased by 70 and 13 times, respectively, with the hybridization of Au-NPs/FPS-K. The highest D* of the Au-NPs/FPS-K/MAPbI3 photodetector was measured to be 7.5 x 1010 Jones at 735 nm excitation. The power and wavelength dependencies of R and D* for the MAPbI3 photodetector were also significantly improved by the Au-NPs/FPS-K hybrid. These results support the development of high -performance perovskite photodetectors utilizing LSPR coupling with the pi-CPE layer.