Applications In Energy Conversion Devices Research Articles

Synthesis of Monodispersed Red Emitting LiAl5O8:Fe3+ Nanophosphors

Efficient wavelength converting nanophosphors are of high demand for their applications in energy conversion devices. We report on the synthesis of well dispersed LiAl5O8:Fe 3+ nanoparticles of homogeneous size and different morphologies by sol–gel method suitable for efficie t wavelength converting devices. Nanoparticles of phase pure Fe3+ doped LiAl5O8 with different shapes and sizes were obtained by varying the pH of the solution in the range of 3–11. X-ray diffraction, transmission electron microscopy and X-ray photoelectron spectroscopy were used to analyze the structure, morphology and composition of the nanoparticles. Incorporation of Fe3+ ions in the LiAl5O8 host lattice has been studied using X-ray photoelectron spectroscopy and electron spin resonance spectroscopy. Emission behavior of the nanophosphors has been studied at room temperature using photoluminescence spectroscopy.

Independent Tuning of the Band Gap and Redox Potential of Graphene Quantum Dots.

The band gap and redox potential of semiconductor nanocrystals are two quantities of primary importance for their applications in energy conversion devices. Herein, we report on covalent functionalization of colloidal graphene quantum dots through a solution-chemistry approach and studies of their band gaps and redox potentials. We show that their band gaps and redox potentials can be independently controlled, the former by size and the latter by functionalization. The size and the functionalization dependence of the properties can be numerically reproduced with tight-binding calculations, which thus provides a simple theoretical tool to guide the design of graphene QDs with desired properties.

Nanostructured carbon and polymer materials – Synthesis and their application in energy conversion devices

In this manuscript, synthesis and its application in energy conversion devices of nanostructured carbon materials like doped fullerene and functionalized doped fullerene with special emphasis on solar cell application has been discussed. An economical solar cell device can be developed using these materials as electron acceptor and nanofibers of conducting polymers as electron donor materials.

Simulations of infrared and optical rectification by geometrically asymmetricmetal–vacuum–metal junctions for applications in energy conversion devices

We use a transfer-matrix methodology to simulate the rectification of infrared and opticalradiation by geometrically asymmetric metal–vacuum–metal junctions in which one of themetals is flat while the other is extended by a tip. We determine in particular the powerthis junction could provide to an external load and the efficiency with which the energy ofincident radiations is converted. We consider first situations in which the external radiationis monochromatic, with typical frequencies in the infrared and optical domains. We thenconsider situations in which the external radiation consists of a full range of frequencies,with amplitudes that are representative of a focused beam of solar radiation. Weinvestigate in particular how the efficiency of the rectification is affected by the aspectratio of the tip, the work function of the metallic elements and the occurrence ofpolarization resonances. Our results demonstrate that the rectification of infrared andoptical radiation is possible using devices of the type considered in this work.They finally provide a quantitative analysis of the efficiency of this rectification.

ZnO/Au Hybrid Nanoarchitectures: Wet-Chemical Synthesis and Structurally Enhanced Photocatalytic Performance

A facile method is introduced to prepare large-area gold-coated ZnO nanorods, featuring the capability to tailor both the spatial distribution and the concentration of metal nanocrystals. The Au nanoparticles-loaded ZnO nanorods exhibit complete catalysis-degradation Rhodamine B within 15 min, which substantially surpass other TiO(2)- and ZnO-based photocatalysts. Furthermore, The ZnO/Au nanocomposites can removal about 91% of environmental persistent 4-chlorophenol from water after 300 min irradiation. The better photocatalytic performance is attributed to the one-dimentional structure of high-quality ZnO nanorods and the large-area noble metal decoration. These promising results would make this photocatalyst an exceptional choice for the environmental purification of organic pollutants in aqueous solution. This approach may also give rise to a new class of multifunctional materials with possible applications in energy-conversion devices, biofunctionalized materials, and infrared-emitting/detecting devices.

Photophysical Properties of Tolan Wavelength Shifters in Solution and Embedded in Polymeric Organic Thin Films

Linear organic conjugated molecules, peripherally equipped with electron-donating and electron-accepting moieties, are recognized as one of the most promising classes of nonlinear optical materials for potential application in energy conversion devices, organic electronics, optical communication, information storage, and nuclear medicine techniques. In this work, we have synthesized and photophysically characterized a series of organic molecules constituted by a 1,2-diphenyl acetylene core (tolan) bearing electronically active groups directly linked to the π-conjugated backbone. Tuning of the absorption and emission energies has been achieved via the push−pull effect. All investigated compounds displayed very high luminescence in condensed media from intramolecular charge transfer excited states with large Stokes shifts. These features revealed to be of particular interest for the engineering of new wavelength shifters for spectral conversion of deep ultraviolet to visible light.

Semiconductor Thin Films Combined With Metallic Grating for Selective Improvement of Thermal Radiative Absorption/Emission

We propose in this work a structure of semiconductor thin films combined with a one-dimensional metallic grating, which allows for selective improvement of thermal radiative absorptivity (also emissivity) of the structure. Both shallow and deep gratings are considered in this work. Our numerical results obtained with a 2D rigorous coupled-wave analysis algorithm demonstrate that the proposed structure exhibits enhanced spectral absorptivity for photon energy slightly above the gap energy of the semiconductor (silicon in this work). Furthermore, the selectively improved absorptivity can be obtained in a wide range of incidence angles. As such, much smaller thickness of the semiconductor layer is required to absorb the same amount of high energy photons than in a conventional Si-based photovoltaic device. In addition, absorptivity for low energy photons in the new structure is lower due to the smaller semiconductor layer thickness. Therefore, the new structure may have potential applications in energy conversion devices.

Electrospinning Nanofibers of PANI/PMMA Blends

ABSTRACTElectrically conducting organic polymers are a novel class of ‘synthetic metals’ that combine the chemical and mechanical properties of polymers with the electronic properties of metals and semiconductors. Electronically conducting polymers have been studied extensively owing to their applications in energy conversion devices, sensors, electro chromic devices, electromagnetic interference shielding (EMI), electronic circuits etc. Polyaniline - an organic conducting polymer - has been blended with poly methyl methacrylate and the blends have been electrospun to produce conducting nanofibers. The electrospun blends have been characterized to study fiber morphology and formulate conditions for nanofiber formation.

Semiconductor inverters for power processing

Flexibility in the application of energy conversion devices may be greatly enhanced by using semiconductor inverters to obtain ac voltages and/or multilevel or high voltage dc. But, design of semiconductor inverters to operate efficiently from the low voltage, high current output of such energy sources as fuel cells, sea cells and single-cell batteries requires careful consideration of semiconductor parameters and their effect upon inverter performance. Comparative advantages and limitations are presented for SCR's, tunnel diodes and transistors as inverter devices. Important device characteristics and their relation to inverter performance are summarized.