This paper describes light trapping in superstrate-type amorphous Si solar cells incorporated with Ag nanostructures (nanodisks) fabricated by a transfer-printing approach. The changes in external quantum efficiency (EQE) and current-voltage characteristics were investigated by changing the position and size (thickness) of the Ag nanodisks in the cells fabricated on flat superstrates. It was confirmed that the optimized Ag nanodisk-configuration led to the enhanced EQE (20%) in the 600-800 nm wavelength range, and the enhanced EQE led to the improved overall conversion efficiency (7.5%) compared to the cell without Ag nanodisks (7.2%). However, the integration of the optimized Ag nanodisk-configuration with the cells fabricated on textured superstrates did not result in the enhanced EQE and conversion efficiency, suggesting further optical designs are necessary to exploit both texture- and plasmon-mediated light trapping effects.

Interest in patterned polymer-based flexible nanodevices and sub-100 nm metal and transparent conducting nanostructured electrodes have led us to modify the traditional nanoimprint lithography technique to enable fabrication of an array of sub-100 nm diameter electrode structures. Transparent conducting electrodes (TCOs) are fabricated by coating one or multiple TCO layers of choice on top of a polymer nanostructured scaffold of appropriate dimension. By optimizing the thickness of each of these layers one may tune and optimize the trade-off between the conductivity and transparency of the sample. Incorporation of plasmonic materials such as Ag leads to interplay of localized and tunable surface plasmon resonances within the TCO structures. At plasmon resonance the reflection of the sample is minimized and absorption in the TCO structures dominates. Experimental and simulated reflection spectra of these structures are in good agreement, including the appearance of sharp spectral features that are absent in a simple planar analog. The simulated Brewster angle of the nanopillars decreases compared to the planar reference sample by up to 10-13 degrees depending on the height of the pillars and indicates a reduced effective refractive index. The depolarization factor obtained by ellipsometry is about 0.05, as anticipated for ellipsoidal pillars.

Hydrogen atom H (≡ proton + electron) transfer (HAT), is the most common reaction that involves the transfer of two elementary particles, a proton and an electron. Antioxidant, proton-coupled electron transfer (PCET) reactions involve also the transfer of two elementary particles, a proton and an electron. These constitute the fundamental step in a wide range of processes, chemical energy technologies, which rely on e–/H+ transfer from combustion and aerobic oxidations, to enzymatic catalysis and the destructive effects of reactive oxygen species in vivo. Here we describe a novel phenomenon, plasmonically-enhanced PCET, using nanothin silica-coated plasmonic Ag nanoparticles, functionalized with gallic acid, a natural antioxidant molecule, that is able to perform PCET. These nanoparticles can transfer rapidly electrons and protons to stable radicals. The kinetics and yield of these PCET reactions can be enhanced by plasmonic resonance modes excited by low-power, near-Infrared (785nm) laser irradiation. The demonstration that these plasmonic nanoparticles can enhance the HAT rates for both electrons and protons expands the traditional view of interfacial PCET. The occurrence of interfacial plasmon-enhancement of PCET brings together so far unrelated domains of nanoplasmonics, electron/proton translocation with significant impact on a variety of applications and most notably in theranostics.

We theoretically and experimentally investigate a novel modulation concept on silicon (Si) based on the combination of quantum confinement and plasmon enhancement effects. We experimentally study the suitability of Ge/SiGe quantum wells (QWs) on Si as the active material for a plasmon-enhanced optical modulator. We demonstrate that in QW structures absorption and modulation of light with transverse magnetic (TM) polarization are greatly enhanced due to favorable selection rules. Later, we theoretically study the plasmon propagation at the metal-Ge/SiGe QW interface. We design a novel Ge/SiGe QW structure that allows maximized overlap between the plasmonic mode and the underlying Ge/SiGe QWs.

Monolayers of arrays of periodic polystyrene (PS) spheres are designed to couple onto the surface of cerium-doped lutetium-yttrium oxyorthosilicate scintillator to improve the light extraction efficiency. The enhancement of extraction efficiency up to 38% relative to the reference case without polystyrene spheres is achieved. Combining with the simulation for the transmission as well as its dispersion relation, detailed analysis of the effect of whispering gallery modes and diffraction on the extraction mechanism are given. As a result, the optimal diameter of 414 nm is obtained based on a trade-off between the transmission loss and the diffraction enhancement.

We improve the efficiency of a bottom-emitting red phosphorescent organic light emitting diode (OLED) by the suppression of wave-guided modes in the bottom contact. ITO as bottom contact layer has been substituted by a thin Ti/Au layer. Electromagnetic simulation results of both devices predict the absence of TE polarized guided contact modes by the use of 10 nm Au as bottom electrode. We measured an improved outcoupling of light which overcompensates absorption losses of the Ti/Au layer in the measured emission cone. By the use of 1 nm Ti as undercoat, a continuous Au film of 8 nm thickness could be realized with an improved transmittance for long wavelengths (λ > 550 nm). As a consequence of fewer lateral guided modes, the external quantum efficiency (EQE) has been enhanced from 11.5 % of the standard device to 14 % of the device with the Ti/Au electrode.

Raman scattering of Si nanowires (NWs) presents antenna effects. The electromagnetic resonance depends on the electromagnetic coupling of the system laser/NW/substrate. The antenna effect of the Raman signal was measured in individual NWs deposited on different substrates, and also free standing NWs in air. The one phonon Raman band in NWs can reach high intensities depending on the system configuration; values of Raman intensity per unit volume more than a few hundred times with respect to bulk substrate can be obtained.

We present results of theoretical and experimental studies of whispering-gallery modes in optical microdisk resonators interacting with subwavelength dielectric particles. We predict theoretically and confirm by direct observations that, contrary to the generally accepted models, both peaks of the particle-induced doublet of resonances are red shifted with respect to the position of the initial resonance.

The effects resulting from the introduction of a controlled perturbation in a single pattern membrane on its absorption are first studied and then analyzed on the basis of band folding considerations. The interest of this approach for photovoltaic applications is finally demonstrated by overcoming the integrated absorption of an optimized single pattern membrane through the introduction of a proper pseudo disordered perturbation.