Localized Surface Plasmon Effect Research Articles

Efficiency roll-off suppression in organic light-emitting diodes using size-tunable bimetallic bowtie nanoantennas at high current densities

Size-tunable bimetallic bowtie nanoantennas have been utilized to suppress the efficiency roll-off characteristics in organic light-emitting diodes (OLEDs) using both the numerical and experimental approaches. The resonant range can be widened by the strong dual-atomic couplings in bimetallic bowtie nanoantennas. Compared with the green OLED with conventional bowtie nanoantennas at a high current density of 800 mA/cm2, the measured efficiency roll-off ratio of the OLED with size-modulated bowtie nanoantennas is decreased from 53.2% to 41.8%, and the measured current efficiency is enhanced by 29.9%. When the size-modulated bowtie nanoantennas are utilized in blue phosphorescent OLEDs, the experimental roll-off ratio is suppressed from 43.6% to 25.9% at 250 mA/cm2, and the measured current efficiency is also enhanced significantly. It is proposed that the efficiency roll-off suppression is mainly related to the enhanced localized surface plasmon effect, which leads to a shorter radiative lifetime.

Contribution of LSP Effect to Light Absorption in Thin-Film Crystalline Silicon Solar Cells

Introducing periodic Ag gratings in the rear side of thin-film silicon excites localized surface plasmon (LSP) and Fabry-Perot (FP) effect. These two effects as well as an intrinsic one pass through absorption overlay together and all contribute to the light absorption in silicon. On the basis of electromagnetic field’s linear superposition, the absorptivity caused by LSP effect is separated from the overall absorptivity of a 500-nm-thick silicon and quantized by short current density. Finite difference time domain (FDTD) calculations were performed to obtain the absorptivity of silicon with different Ag grating parameters. The contribution of LSP effect to the light absorption is evaluated by photocurrent ratio and investigated under different Ag grating parameters. It is found that, as LSP effect is excited most intensively, the light absorption of silicon will also be enhanced extremely. By careful design, the overall short current density of silicon is optimized up to 25.4 mA/cm2, where the contribution of LSP effect accounts for 38.6 %. Comparing to 14.5 mA/cm2 for a reference silicon stack, it increases up to almost 75 %. These results may give design suggestions in implementation of plasmonic solar cell as high efficiency devices.

Efficiency roll-off suppression in organic light-emitting diodes at high current densities using gold bowtie nanoantennas

In this study, large-scale gold (Au) bowtie nanoantennas have been utilized to suppress the efficiency roll-off in organic light-emitting diodes (OLEDs) numerically and experimentally. Compared with the OLED without nanoantennas, the experimental roll-off ratio of the OLED with Au bowtie nanoantennas significantly decreases from 59.4 to 51.3% at a high current density of 1000 mA/cm2. We attribute the roll-off suppression to the localized surface plasmon (LSP) effect, which leads to a shorter radiative lifetime. The insufficient coupling between radiated light and LSP resonance could also be improved by a strong resonance coupling between the tips of bowtie nanoantennas.

The synergistic effect of a well-defined Au@Pt core-shell nanostructure toward photocatalytic hydrogen generation: interface engineering to improve the Schottky barrier and hydrogen-evolved kinetics.

A well-defined co-catalyst system TiO2 nanotube-Au (core)-Pt (shell) was demonstrated to be the combination of the localized surface plasmon effect of gold and excellent proton reduction nature of platinum. Furthermore, surface engineering by the descending Fermi energies of gold and platinum was beneficial to electron transfer.

Annealed silver-islands for enhanced optical absorption in organic solar cell

Silver nano-islands are explored for enhancing optical absorption and photo-conversion efficiency in organic solar cells (OSCs) based on the surface plasmon resonance effect under diverse annealing conditions. Ag nano-islands have been deposited by RF magnetron sputtering at 15W for 10s and subsequently annealed between 100°C–250°C in air and Argon ambient. The optical properties of the reconstructed Ag islands demonstrate an increase and a blue shift in the absorption bands with increasing annealing temperature. This is the localized surface plasmon effect due to the Ag islands of diverse sizes, shapes and coverages. The increase in optical absorption with temperature is attributed to changes in island shape and density as collaborated by atomic force microscopy and TEM.As a proof of concept, an organic solar cell was characterized for current–voltage (I–V) measurements under dark and under solar simulated white light. Incorporation of annealed Ag islands has yielded an efficiency increment of between 4–24%.

Effect of localized surface plasmon and surface plasmon polariton modes on properties of metamaterials

Effect of localized surface plasmon and surface plasmon polariton modes on properties of metamaterials

Enhancement of the power conversion efficiency for inverted organic photovoltaic devices due to the localized surface plasmonic resonant effect of Au nanoparticles embedded in ZnO nanoparticles

The absorption spectra and input photon-to-converted current efficiency curves showed that Au nanoparticles increased the plasmonic broadband light absorption, thereby enhancing the short-circuit current density of the inverted organic photovoltaic (OPV) cells with a Au–ZnO nanocomposite electron transport layer (ETL). The power conversion efficiency of the inverted OPV cell fabricated with a Au–ZnO nanocomposite ETL was higher by 40% than that of the inverted OPV cell fabricated with a ZnO nanoparticle ETL, which could be attributed to the enhanced photon absorption in the active layer due to the localized surface plasmonic resonance of the Au nanoparticles.

Polarization sensitivity of light diffraction for periodic array of anisotropic gold nanoparticles

This article aims to analyze the first order diffraction intensity of the incident polarized light which is diffracted by the gold nanoparticles array in terms of the surface plasmon effect. The inspected gold nanoparticles array films are built in grating pattern with stripe thickness of 4 μm and diameters of gold nanoparticles ca. 10–56 nm, which are formed by annealing at temperatures of 400, 450, 500, and 550 °C, respectively. The probing light is linearly polarized with wavelengths of 450–800 nm and counterclockwise turns its polarization direction from 0° to 90° during measurements. The results show that the diffraction intensity depends on the anisotropic configuration samples which gold nanoparticles are orientated by analyzing the scanning electron microscope images. It results that the localized surface plasmon effect induced by incident field depends on orientation and causes the sample polarization-sensitive.

Photoluminescence enhancement in few-layer WS2 films via Au nanoparticles

Nano-composites of two-dimensional atomic layered WS2 and Au nanoparticles (AuNPs) have been fabricated by sulfurization of sputtered W films followed by immersing into HAuCl4 aqueous solution. The morphology, structure and AuNPs distribution have been characterized by electron microscopy. The decorated AuNPs can be more densely formed on the edge and defective sites of triangle WS2. We have compared the optical absorption and photoluminescence of bare WS2 and Au-decorated WS2 layers. Enhancement in the photoluminescence is observed in the Au-WS2 nano-composites, attributed to localized surface plasmonic effect. This work provides the possibility to develop photonic application in two-dimensional materials.

Polymer blend lithography for metal films: large-area patterning with over 1 billion holes/inch(2).

Polymer blend lithography (PBL) is a spin-coating-based technique that makes use of the purely lateral phase separation between two immiscible polymers to fabricate large area nanoscale patterns. In our earlier work (Huang et al. 2012), PBL was demonstrated for the fabrication of patterned self-assembled monolayers. Here, we report a new method based on the technique of polymer blend lithography that allows for the fabrication of metal island arrays or perforated metal films on the nanometer scale, the metal PBL. As the polymer blend system in this work, a mixture of polystyrene (PS) and poly(methyl methacrylate) (PMMA), dissolved in methyl ethyl ketone (MEK) is used. This system forms a purely lateral structure on the substrate at controlled humidity, which means that PS droplets are formed in a PMMA matrix, whereby both phases have direct contact both to the substrate and to the air interface. Therefore, a subsequent selective dissolution of either the PS or PMMA component leaves behind a nanostructured film which can be used as a lithographic mask. We use this lithographic mask for the fabrication of metal patterns by thermal evaporation of the metal, followed by a lift-off process. As a consequence, the resulting metal nanostructure is an exact replica of the pattern of the selectively removed polymer (either a perforated metal film or metal islands). The minimum diameter of these holes or metal islands demonstrated here is about 50 nm. Au, Pd, Cu, Cr and Al templates were fabricated in this work by metal PBL. The wavelength-selective optical transmission spectra due to the localized surface plasmonic effect of the holes in perforated Al films were investigated and compared to the respective hole diameter histograms.

Enhancement of photoluminescence efficiency from semi-polar InGaN/GaN multiple quantum wells with silver metal

We have studied the effect of surface plasmon polariton (SPP) and localized surface plasmon (LSP) on the emission of semi-polar InGaN/GaN light emitting diode (LED) with multi-quantum wells structure. From the photoluminescence (PL) measurement at room temperature, spectrally-integrated enhancements of semi-polar SPP LEDs with 15 and 40-nm-thick Ag films were 1.7 and 2.9, respectively. The absorbance peak of Ag nanoparticles was red-shifted as diameter of Ag nanoparticles increases. However, the absorbance peak of Au nanoparticles was not related with their diameters. Spectrally-integrated enhancement of semi-polar LSP LED with 250-nm-diameter Ag nanoparticles was shown to 1.3. These results showed that the blue emission of semi-polar InGaN/GaN LED can be improved by SPP and LSP.

Device performance of inverted polymer solar cells with AgSiO(2) nanoparticles in active layer.

PSS) was prepared due to the efficient insertion of Ag/SiO(2) NPs in the vicinity of active layer, which led to an enhancement in photo-conversion efficiency (PCE). This enhancement mainly comes from the light scattering by the SiO(2) shell and the localized surface plasmon effect by the Ag core, but we also considered the structural issues such as the NP distribution, the swelling of the active layer and of the metal electrode.

Investigation of the localized surface plasmon effect from Au nanoparticles in ZnO nanorods for enhancing the performance of polymer solar cells.

The organic polymer solar cell is recognized as one of the most competitive technologies of the next generation. Au nanoparticles and ZnO nanorods were combined to improve the inverted-structure low-bandgap polymer solar cells and enhance the absorption and efficiency of the devices. However, the Au nanoparticles tend to aggregate in solution, thus reducing the localized surface plasmon resonance (LSPR) effect. The cluster effect on the spectral range of enhancement in the absorption is investigated and the absorption characteristics of the LSPR receive proper modification through our experiment. After reducing the number of Au nanoparticle clusters, the LSPR effect in the devices was clearly verified. The proper combination of the Au nanoparticles and ZnO nanorods leads to the power conversion efficiency of the PTB7 : PC71BM inverted organic solar cell reaching 8.04% after optimizing the process conditions.

Surface-plasmon-enhanced microcavity organic light-emitting diodes.

Efficiency enhancement of organic light-emitting diodes (OLEDs) can be obtained by the combination of microcavity effect and Au nanoparticles based surface plasmons. Au nanoparticles are thermally deposited on distributed Bragg reflector (DBR)-coated glass substrate, leading to realization of microcavity effect and localized surface plasmon effect. Our results show the current efficiency of OLEDs with DBR/Au nanoparticles as anode is increased by 72% compared to that with ITO as anode.

Efficiency enhancement of organic light-emitting devices due to the localized surface plasmonic resonant effect of Au nanoparticles embedded in ZnO nanoparticles

Organic light-emitting devices (OLEDs) were fabricated utilizing Au-ZnO nanocomposites (NCs) with various Au nanoparticles (NPs) concentrations synthesized by using a sol-gel process to enhance their current efficiency, and these devices were compared with OLEDs fabricated utilizing ZnO NPs only. The electroluminescence intensity of the OLEDs with Au-ZnO NCs at a wavelength of 535 nm was significantly larger than that of the OLEDs with ZnO NPs by a factor of 1.89. The current efficiency of the OLEDs with 10 wt. % Au-ZnO NCs at 1000 cd/m2 was higher by 16.7 cd/A than that of the OLEDs with ZnO NPs. This increase in the current efficiency of the OLEDs with Au-ZnO NCs was attributed to an enhancement of the out-coupling efficiency due to the existence of the localized surface plasmonic resonance effect induced by the Au NPs that were embedded in the Au-ZnO NCs.

Numerical Study of Polarization-Dependent Emission Properties of Localized-Surface-Plasmon-Coupled Light Emitting Diodes with Ag/SiO2 Na

We study polarization-dependent spontaneous emission (SE) rate and light extraction efficiency (LEE) in localized-surface-plasmon (LSP)-coupled light emitting diodes (LEDs). The closely packed seven $Ag/SiO_2$ core-shell (CS) nanoparticles (NPs) lie on top of the GaN surface for LSP coupling with a radiated dipole. According to the dipole direction, both the SE rate and the LEE are significantly modified by the LSP effect at the $Ag/SiO_2$ CS NPs when the size of Ag, the thickness of $SiO_2$ , and the position of the dipole source are varied. The enhancement of the SE rate is related to an induced dipole effect at the Ag, and the high LEE is caused by light scattering with an LSP mode at $Ag/SiO_2$ CS NPs. We suggest the optimum position of the quantum well (QW) in blue InGaN/GaN LEDs with $Ag/SiO_2$ CS NPs for practical application.

A Short Pulse, Narrow Band Distributed Feedback Dye Laser Using Nanoparticle-doped Dye Solution Active Medium

Spherical gold nanoparticles doped dye solution was used for laser active medium. Fluorescence and absorption spectral shapes of laser dye molecules were modified by the resonance energy transfer between gold nanoparticles due to localized surface plasmon effect. Laser pulse width and tuning range of a distributed feedback dye laser can be controlled by using various gold nanoparticle concentrations. The gold nanoparticles can be considered as a quenching element inside laser cavity to remove relaxation oscillation pulses at high pumping rate above threshold.

Near-infrared optical absorption enhanced in black silicon via Ag nanoparticle-induced localized surface plasmon.

Due to the localized surface plasmon (LSP) effect induced by Ag nanoparticles inside black silicon, the optical absorption of black silicon is enhanced dramatically in near-infrared range (1,100 to 2,500 nm). The black silicon with Ag nanoparticles shows much higher absorption than black silicon fabricated by chemical etching or reactive ion etching over ultraviolet to near-infrared (UV-VIS-NIR, 250 to 2,500 nm). The maximum absorption even increased up to 93.6% in the NIR range (820 to 2,500 nm). The high absorption in NIR range makes LSP-enhanced black silicon a potential material used for NIR-sensitive optoelectronic device.PACS78.67.Bf; 78.30.Fs; 78.40.-q; 42.70.Gi

Optics–electrics highways: Plasmonic silver nanowires@TiO2 core–shell nanocomposites for enhanced dye-sensitized solar cells performance

In this article, the unique bristled silver nanowires@TiO2 core–shell nanostructure (AgNW@TiO2) is introduced into the TiO2 photoanode and applied to assemble dye-sensitized solar cells (DSSCs). The effects of the “optics–electrics highways” composites on the photovoltaic and photocatalytic behaviors of DSSCs are investigated in detail. Experiment research and FDTD simulation indicate that both the localized surface plasmon resonance (LSPR) and plasmonic waveguide effect could enhance light harvesting efficiency. By electrical properties and electrochemical analysis, it is demonstrated that the AgNW@TiO2 significantly accelerates electron transport as well as reduces recombination, then the charge collection efficiency of DSSCs is improved. The composite-modified DSSC exhibits the best performance with the power conversion efficiency of 8.84% which is superior to that of the free–modified DSSC with the PCE of 6.16%.

Systematic approach of nanoparticle design to enhance the broadband plasmonic scattering effect

To overcome low conversion efficiency of thin film solar cells, using the localized surface plasmon effect caused by the interaction between the incident beam and metallic nanoparticles inserted in or on the absorbing layer can be a promising alternative to overcome the low efficiency problem. Detail shape and size of nanoparticles are directly related with the localized surface plasmon effect as well as optical properties; however, their detail shape and size are hard to be determined depending only on the theoretical or experimental approach. Therefore, the method focusing on defining structural boundaries would be a useful method for nano or microscale design to generate simple and clear shape. In this study, we adopted the structural optimization scheme based on the phase field method to determine the optimal shape of a silver (Ag) nanoparticle positioned on the upper surface of the absorbing layer. We carried out the design process for broadband wavelength to be taken into account and verified the plasmonic scattering effect enhancement in the absorbing layer by numerical simulations.