Enhanced Spatial Light Confinement of All Inorganic Perovskite Photodetectors Based on Hybrid Plasmonic Nanostructures

3D incident light confinement by radical electromagnetic fields offers a facile and novel way to break through the performance limit of inorganic perovskite CsPbBr3 quantum dots (QDs). Herein, metallic nanoparticles decorated anodic aluminum oxide (AAO) hybrid plasmonic nanostructures with geometric control are first proposed for cyclic light utilization of perovskite photodetectors, enabled by spatially extended light confinement. The drastic multiple interference induced by plasmonic coupling within AAO matrixes are generated as a function of pore sizes, which can effectively collect the transmitted photons back to the surface. In addition, the self‐assembled metallic nanoparticles simultaneously concentrate the incident and reflected light beams into the CsPbBr3 QD layers. The light confinement inherently stems from the metallic nanoparticles due to the variation of the near surface electromagnetic fields. As a result, perovskite photodetectors based on Al nanoparticles/AAO hybrid plasmonic nanostructures with a pore size of 220 nm exhibit enhanced photoresponse behavior with remarkably increased photocurrent by ≈43× and maintain low dark current under 490 nm light illumination at 1 V. The multiple‐interference in anodic aluminium oxide matrixes effectively captures the transmitted photons and reflects back to the surface, and cyclically concentrated with metallic nanoparticles on the hybrid plasmonic nanostructures. Spatially extended light confinement radically boosts the generation of electron–hole pairs from the photoactive layers. The performance of the photodetectors exhibits a strong dependence on configuration of the nanostructures.