Interactions of Light, Surface Plasmons and Excitons in Bilayers of FAPbI₃ Nanocrystals with Core–Shell Au/SiO₂ Nanoparticles

Integration of plasmonic nanostructures into perovskites is an effective way to enhance and tailor light–matter interactions, resulting in further improvement of the already impressive intrinsic photonic properties of the perovskites. Despite remarkable recent progress, the complex mechanisms via which light, excitons and plasmons interact in such hybrid structures are not fully understood. Herein, plasmonic-perovskite structures in bilayer configuration are produced by the deposition of formamidinium lead triiodide (FAPbI3) nanocrystals (NCs) on top of a core–shell gold-silica (Au/SiO2) nanoparticle (NP) underlayer. By tuning the NP core and shell size, a 5-fold enhancement of the macroscopic absorption and luminescence in the vicinity of the localized surface plasmon (LSP) resonance can be achieved in the bilayers compared to reference, pristine FAPbI3 NCs films. Optical spectroscopy performed both at the ensemble and at the few particle level, supported by numerical simulations allow to disentangle the contributions of near-field LSP-exciton and far-field LSP-light interactions that result in the enhancement of the light absorption and light emission. Based on our results, far field light scattering by the LSP results in photon recycling within the perovskite NCs layer, effectively increasing light absorption and light emission. Near-field energy transfer from the metal NPs to the semiconductor NCs contributes less but becomes significant for the case of large core and small shell NPs due to the increased spectral overlap and closer proximity of the surface plasmons and excitons, respectively.