We demonstrate that incorporation of octadecyltrimethoxysilane (OTMS)-functionalized, spectrally tuned, gold/silica (Au/SiO2) core/shell nanospheres and nanorods into the active layer of an organic photovoltaic (OPV) device led to an increase in photoconversion efficiency (PCE). A silica shell layer was added onto Au core nanospheres and nanorods in order to provide an electrically insulating surface that does not interfere with carrier generation and transport inside the active layer. Functionalization of the Au/SiO2 core/shell nanoparticles with the OTMS organic ligand was then necessary to transfer the Au/SiO2 core/shell nanoparticles from an ethanol solution into an OPV polymer-compatible solvent, such as dichlorobenzene. The OTMS-functionalized Au/SiO2 core/shell nanorods and nanospheres were then incorporated into the active layers of two OPV polymer systems: a poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCB60M) OPV device and a poly[2,6-4,8-di(5-ethylhexylthienyl)benzo[1,2-b;3,4-b]dithiophene-alt-5-dibutyloctyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]pyrrole-1,4-dione] (PBDTT-DPP:PC60BM) OPV device. For the P3HT:PC60BM polymer with a band edge of ~700 nm, the addition of the core/shell nanorods with an aspect ratio (AR) of ~2.5 (extinction peak ~670 nm) resulted in a 7.1% improvement in PCE, while for the PBDTT-DPP:PC60BM polymer with a band edge of ~860 nm, the addition of core/shell nanorods with an AR of ~4 (extinction peak ~830 nm) resulted in a 14.4% improvement in PCE. The addition of Au/SiO2 core/shell nanospheres to the P3HT:PC60BM polymer resulted in a 2.7% improvement in PCE, while their addition to a PBDTT-DPP:PC60BM polymer resulted in a 9.1% improvement. The PCE and Jsc enhancements were consistent with external quantum efficiency (EQE) measurements, and the EQE enhancements spectrally matched the extinction spectra of Au/SiO2 nanospheres and nanorods in both OPV polymer systems.

Silicon nitride films were deposited using an atmospheric pressure plasma source. The discharge was produced by flowing nitrogen and helium through two perforated metal electrodes that were driven by 13.56 MHz radio frequency power. Deposition occurred by mixing the plasma effluent with silane and directing the flow onto a rotating silicon wafer heated to between 100˚C and 500˚C. Film growth rates ranged from 90 ± 10 to 1300 ± 130 Å min −1. Varying the N 2 /SiH 4 feed ratio from 55.0 to 5.5 caused the film stochiometry to shift from SiN 1.45 to SiN 1.2. Minimum impurity concentrations of 0.04% carbon, 3.6% oxygen and 13.6% hydrogen were achieved at 500˚C, and an N 2 /SiH 4 feed ratio of 22.0. The growth rate increased with increasing silane and nitrogen partial pressures, but was invariant with respect to substrate temperature and rotational speed. The deposition rate also decreased sharply with distance from the plasma. These results combined with emission spectra taken of the afterglow suggest that gas-phase reactions between nitrogen atoms and silane play an important role in this process.

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We present an experimental demonstration of passive, dynamic thermal regulation in a solid-state system with temperature-dependent thermal emissivity switching. We achieve this effect using a multilayered device, comprised of a vanadium dioxide (Vo 2) thin film on a silicon substrate with a gold back reflector. We experimentally characterize the optical properties of the VO 2 film and use the results to optimize device design. Using a calibrated, transient calorimetry experiment we directly measure the temperature fluctuations arising from a time-varying heat load. Under laboratory conditions, we find that the device regulates temperature better than a constant emissivity sample. We use the experimental results to validate our thermal model, which can be used to predict device performance under the conditions of outer space. In this limit, thermal fluctuations are halved with reference to a constant-emissivity sample. The use of material design techniques to control the thermal emissive properties of matter has emerged as topic of great interest in current research of intelligent, radiative thermal control. A variety of microstructures have been used for this purpose, including multilayer films 1,2 , microparticles 3 , photonic crystals 4 , and metamaterials 5-7. These structures have been extensively studied for passive radiative cooling applications, which offer significant energy savings due to their ability to operate without external power. Beyond cooling, one particularly interesting application of emissive control is the design of materials that self-regulate their temperature 8,9 , a property we term thermal homeostasis 10,11. Such a capability is likely to be useful for a variety of applications including satellite thermal control, for which traditional solutions require either electrical power or moving parts 12-15. The key physical principle required for passive thermal regulation is strong temperature-dependent integrated emissivity. The phase change material vanadium dioxide (VO 2), in particular, exhibits a dramatic change to its optical properties across a thermally narrow phase transition 16,17. With proper design, VO 2-based microstructures can achieve a sharp increase in thermal emissivity across the phase transition temperature near 68 °C 17,18. Intuitively, when the material temperature is below the transition temperature, the emissivity is low, and the object retains heat. When the material temperature exceeds the transition temperature, emissivity increases, and the object loses heat. This negative feedback regulates the material near the temperature of the phase transition 10. Recent works have demonstrated experimentally broadband emissivity switching for both planar 19 and metareflector designs 20. However, no direct measurement of thermal regulation has been performed. In this paper, we present an experimental method for studying dynamic thermal regulation due to infrared emissive switching. We therefore demonstrate direct evidence of reduction in thermal fluctuations due to emissive swi...

We theoretically investigate a nanoscale mode-division multiplexing scheme based on parity-time (PT ) symmetric coaxial plasmonic waveguides. Coaxial waveguides support paired degenerate modes corresponding to distinct orbital angular momentum states. PT symmetric inclusions of gain and loss break the degeneracy of the paired modes and create new hybrid modes without orbital angular momentum. This process can be made thresholdless by matching the mode order with the number of gain and loss sections within the coaxial ring. Using both a Hamiltonian formulation and degenerate perturbation theory, we show how the wavevectors and fields evolve with increased loss/gain and derive sufficient conditions for thresholdless transitions. As a multiplexing filter, this PT symmetric coaxial waveguide could help double density rates in on-chip nanophotonic networks.

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