Ag@SiO2耦合结构设计及其对薄膜太阳电池的响应调控

Ag@SiO2纳米耦合结构同时具有等离激发和衍射散射特性,可有效调控光波的行进路径和能量分布,在薄膜太阳电池陷光领域极具潜力.本文基于时域有限差分方法和严格耦合波分析,建立三维电磁仿真模型,研究Ag@SiO2耦合结构对非晶硅电池光谱响应的调控机理,通过优化设计,得到高陷光电池器件.结果表明:当Ag和SiO2特征尺寸分别为18和150 nm时,共振波和衍射波达到最优耦合,通过耦合结构进入电池响应层的透射光谱最大,相应量子效率显著增强.与同尺寸的平面电池相比,其光电转换效率从7.19%提高到7.80%,相对提高了8.48%.

Plasmonic Field Enhancement for Vibration Spectroscopy at Metal/Water Interfaces

Electrochemical （EC） reactions play vital roles in many disciplines, and its molecular-level understanding is highly desired, in particular under reactions. The vibration spectroscopy is a powerful in situ technique for chemical analysis, yet its application to EC reactions is hindered by the strong attenuation of infrared （IR） light in both electrodes and electrolytes. Here we demonstrate that by incorporating appropriate sub-wavelength plasmonic structures at the metal electrode, the IR field at the EC interface can be greatly enhanced via the excitation of surface plasmon. This scheme facilitates in situ vibrational spectroscopic studies, especially using the surface-specific sum-frequency generation technique.

Tunneling Electron Induced Fluorescence from Single Porphyrin Molecules Decoupled by Striped-Phase Octanethiol Self-assembled Monolayer

We investigate tunneling electron induced luminescence from isolated single porphyrin molecules that are decoupled by striped-phase self-assembled monolayer of octanethiol from the underneath Au（111） substrate. Intrinsic single-molecule electroluminescence has been realized by such decoupling at both bias polarities. The photon emission intensity acquired from the molecular lobe is found stronger than that from the molecular center. These re- sults provide useful information on the understanding of electroluminescent behavior and mechanism in molecular tunnel junctions.

Self-assembly of α-6T Molecule on Ag（100） and Related STM Induced Luminescence

We have investigated the self-assembly and light emission properties of organic α- sexithiophene （α-6T） molecules on Ag（100） under different coverage by scanning tunneling microscopy （STM）. At very low coverage, the α-6T molecules form a unique enantiomer by grouping four molecules into a windmill supermolecular structure. As the coverage is increased,α-6T molecules tend to pack side by side into a denser stripe structure. Further increase of the coverage will lead to the layer-by-layer growth of molecules on Ag（100） with the lower-layer stripe pattern serving as a template. Molecular fluorescence for α-6T molecules on Ag（100） at a coverage of five monolayers has been detected by light excitations, which indicates a well decoupled electronic states for the top-layer α-6T molecules. However, the STM induced luminescent spectra for the same sample reveal only plasmonic-like emission. The absence of intramolecular fluorescence in this case suggests that the electronic decoupling is not a sufficient condition for generating photon emission from molecules. For intramolecular fluorescence to occur, the orientation of the dynamic dipole moment of molecules and the energy-level alignment at the molecule-metal interface are also important so that molecules can be effectively excited through efficient dipolar coupling with local plasmons and by injecting holes into the molecules.

Surface Plasmon Polaritons of Two-Dimensional Three-Order Dendritic Structures

We study surface plasmon polaritons excited on two-dimensional three-order dendritic structures. Previous studies show that split ring resonators （SRRs） can be used to obtain magnetic resonance, thus sustairdng surface waves behaving like surface plasmon polaritons （SPPs）. In this paper, we obtain detailed results on surface plasmon polaritons of several different grating structures and theoretically prove that this kind of structures can sustain SPPs. Besides, since dendritic structures can be fabricated by double template-assisted electrochemical deposition, it is worth noting that fabrication of SPP-based materials might be much easier.

Coulomb Screening and Plasmon Excitation in Graphene at Finite Temperature

By using the random phase approximation (RPA) in many-body perturbation theory,we calculate thepolarization function of the electron gas in graphene at finite temperature.Based on this,we calculate the temperaturedependent dielectric function ∈(q).The thermal effect on ∈(q) in various q regions is discussed.The temperaturedependence is found to be quadratic.We also investigate the plasmon dispersion relation at finite temperature,with thezero-temperature relation as a special case.The result is in good agreement with recent experimental data.

Optical diffraction gratings embedded in BK-7 glass by low-density plasma formation using femtosecond laser

The optical embedded diffraction gratings with the internal refractive index modification in BK-7 glass plates were demonstrated using low-density plasma formation excited by a high-intensity femtosecond （130 fs） Ti： sapphire laser （λp=790 rim）. The refractive index modifications with diameters ranging from 400 nm to 4 gm were photoinduced after plasma formation occurred upon irradiation with peak intensities of more than 1 ×10^13 W/cm2. The graded refractive index profile was fabricated to be a symmetric around the center of the point at which low-density plasma occurred. The maximum refractive index change （An） was estimated to be 1.5x10 2. Several optical embedded gratings in BK-7 glass plate were demonstrated with refractive index modification induced by the scanning of low-density plasma formation.

Electron-plasmon interaction induced plasmonic-polaron band replication in epitaxial perovskite SrIrO_(3) films

Electron-boson interaction is fundamental to a thorough understanding of various exotic properties emerging in many-body physics. In photoemission spectroscopy, photoelectron emission due to photon absorption would trigger diverse collective excitations in solids, including the emergence of phonons,magnons, electron-hole pairs, and plasmons, which naturally provides a reliable pathway to study electron-boson couplings. While fingerprints of electron–phonon/-magnon interactions in this state-ofthe-art technique have been well investigated, much less is known about electron-plasmon coupling,and direct observation of the band renormalization solely due to electron-plasmon interactions is extremely challenging. Here by utilizing integrated oxide molecular-beam epitaxy and angle-resolved photoemission spectroscopy, we discover the long sought-after pure electron-plasmon couplinginduced low-lying plasmonic-polaron replica bands in epitaxial semimetallic SrIrO_(3) films, in which the characteristic low carrier concentration and narrow bandwidth combine to provide a unique platform where the electron-plasmon interaction can be investigated kinematically in photoemission spectroscopy. This finding enriches the forms of electron band normalization on collective modes in solids and demonstrates that, to obtain a complete understanding of the quasiparticle dynamics in 5 d electron systems, the electron-plasmon interaction should be considered on equal footing with the acknowledged electron–electron interaction and spin–orbit coupling.

A novel strategy for improving upconversion luminescence of NaYF4：Yb, Er nanocrystals by coupling with hybrids of silver plasmon nanostructures and poly（methyl methacrylate） photonic crystals

The coupling of upconversion nanophosphors （UCNPs） with the surface plasmonic resonance （SPR） of noble metals is a promising way to improve luminescent efficiency of UCNPs; however, it is still a challenge to achieve stable, reproducible and effective upconversion luminescence （UCL） enhancement through such coupling. In this work, we present a novel strategy to improve UCL of NaYF4：ybB,Er3. UCNPs, by combining the near-field coupling of SPR of silver and the far-field coupling of poly（methyl methacrylate） （PMMA） opal photonic crystals （OPCs） with the UCNPs. In order to control the effective interaction distance between the UCNPs and the SPR, a porous silver film consisting of randomly distributed silver nanoparticles （NPs） （〉 100 nm） was prepared which demonstrated strong SPR over a broad wavelength range, and its coupling to the UCNPs was found to be much stronger than that of a dense film. In the far-field coupling of OPCs, the photonic stop band （PSB） of the PMMA OPCs was tuned to 980 nm, matching exactly the excitation light. By modulating the particle size of the UCNPs, and the direction and excitation power of the incident light, a maximum enhancement of 60-fold was observed, which is an important advance for metaMnduced UCL enhancement systems.

Nanoplasmonic colloidal suspensions for the enhance-ment of the luminescent emission from single-walled carbon nanotubes

Aiming to enhance the luminescence yield of carbon nanotubes, we introduce a new class of hybrid nanoplasmonic colloidal systems （π-hybrids）. Nanotubes dispersed in gold nanorod colloidal suspensions yield hybrid structures exhibiting enhanced luminescence up to a factor of 20. The novelty of the proposed enhancement mechanism relies on including metal proximity effects in addition to its localized surface plasmons. This simple, robust and flexible technique enhances the luminescence of nanotubes with chiralities whose enhancement has never reported before, for example the （8,4） tube.

Anisotropic Intervalley Plasmon Excitations in Graphene

We investigate theoretically the intervalley plasmon excitations(IPEs) in graphene monolayer within the random-phase approximation. We derive an analytical expression of the real part of the dielectric function. We find a lowenergy plasmon mode with a linear anisotropic dispersion which depends on the Fermi energy and the dielectric constant of substrate. The IPEs show strongly anisotropic behavior, which becomes significant around the zigzag crystallographic direction. More interestingly, the group velocity of IPE varies from negative to positive, and vanishes at special energy.