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Localized surface plasmon resonances in metallic nanostructures have been extensively harnessed for light absorption enhancement in various solar cells, including perovskite solar cells (PSCs). For stabilization and functionalization, plasmonic metal nanostructures are often coated with dielectric shells. In this work, we numerically investigate the effects of dielectric coated plasmonic metal nanoparticles (NPs) on solar absorption enhancement in perovskite thin films. To our surprise, a further absorption enhancement compared with the films embedding bare Ag NPs can be achieved when using thin dielectric coating of high refractive index, while an absorption reduction in comparison with bare perovskite thin films may take place when the embedded Ag NPs are coated with thick dielectric shells of low refractive index. The physics behind is addressed within classic electrodynamics. These anomalous effects extend our knowledge of PSCs, providing guidelines for optimized design of plasmonic solar cells. [ABSTRACT FROM AUTHOR]

For stabilization and functionalization, plasmonic nanoparticles (NPs) are often coated with dielectric shells, yet suffer from the weakening of local electric field enhancement. Herein, we numerically demonstrate that, instead of being weakened, the local electric fields can be further enhanced using an appropriate high refractive index dielectric coating. Because the high refractive index dielectric shell owns strong Mie resonances that can participate in the bonding plasmon hybridization, it can avoid excessive diminishing of light absorption when the shell becomes thick. Meanwhile, it can sustain a great leap of the local electric fields reaching the surface, which follows the boundary conditions at the interface within electrodynamics. The two mechanisms can work synergistically to offset the decay of the local electric fields inside the shell. It is also worth noting that a dielectric shell with too high a refractive index may badly suppress the light scattering by the core–shell NPs, going against the light coupling effect. These findings are of significant importance in extended applications of surface enhanced spectroscopies, especially for shell-isolated NP-enhanced Raman spectroscopy and surface enhanced fluorescence. [ABSTRACT FROM AUTHOR]

The design of antenna–reactor photocatalysts has become a powerful strategy to covert transition metal reactors from traditional thermocatalysts to novel photocatalysts. Plasmonic metals are often used as the optical antenna. Here, we demonstrate that conventional dielectric supports with high refractive index are able to achieve comparable performance as the plasmonic antennas, giving rise to a huge enhancement of the visible light absorption in the small Pt nanoparticles (NPs) of the core–satellite antenna–reactor photocatalysts through resonance energy transfer. The absorption enhancement can be mediated not only by the electric resonances of the plasmonic antenna but also by the magnetic resonances of the dielectric antenna. A large enough dielectric antenna or a small plasmonic antenna is desired for the generation of strong optical resonances. Judged by those Pt NPs with strong visible light absorption enhancement, the potential catalytically active sites are mainly distributed at the back side of the dielectric antenna, while they may be widely distributed over the surface of the plasmonic antenna with probably lower activities. The expanding scope of antenna–reactor photocatalysts offers new opportunities for solar to chemical energy conversion using nonplasmonic catalytic transition metals. [ABSTRACT FROM AUTHOR]

As a promising plasmonic photocatalyst, an Ag-Pt core-shell nanostructure is able to convert sunlight into chemical energy. To fully exploit each function of the constituent materials, a numerical study on the optimal design of the hybrid nanostructures is presented in this work. Ag-Pt is demonstrated to be a good material configuration for the core-shell nanostructure because Ag has strong intrinsic plasmonic responses and a low imaginary dielectric function in the visible region, while Pt is catalytically active and has a large imaginary dielectric function. Considering the hot carrier generation and transfer processes in both plasmonic photocatalysis and photothermal catalysis, the catalytically active sites at the Pt shell can be revealed by high local heating power densities. For the dipole resonance, these sites distribute alternately with the spots where local electric fields are greatly enhanced. The former are along the "equatorial belt" of the nanoparticle, while the latter are in the two polar regions. It is then found that the high-efficiency hot carrier generation is related to multiple factors, including at least an ultrathin shell and a core of high aspect ratio with sharp tips. The physics behind these factors is further addressed. [ABSTRACT FROM AUTHOR]

Strong near‐field coupling between small catalytic Pt nanoparticles (NPs) and their dielectric supports can be achieved while visible light absorption in the Pt NPs is greatly enhanced via rationally designing the dielectric–Pt core–satellite configuration. Herein, it is demonstrated that the absorption enhancement is mediated by the Mie resonances of the support and the absorption peaks are induced by the magnetic Mie resonances. Utilizing both multipole decomposition analysis and numerical near‐field mapping, resonances including magnetic dipole, magnetic quadrupole, and higher modes are verified. For the generation of strong Mie resonances, a dielectric support with a high refractive index, like TiO2, can be used not only as the core directly, but also as a shell coated beneath or above the Pt NP layer. Additionally, the redshifts between the absorption peaks contributed by the Pt NPs and the scattering peaks contributed by the dielectric core are ascribed to the intrinsical spectral deviation between near‐ and far‐field optical properties. These findings benefit significantly both the fundamental understanding and optimized design of dielectric supported Pt photocatalysts, providing new opportunities for solar energy conversion and visible light photocatalysis using nonplasmonic catalytic transition metals. [ABSTRACT FROM AUTHOR]