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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2019

Spin-optoelectronic devices based on hybrid organic-inorganic trihalide perovskites

Recently the hybrid organic-inorganic trihalide perovskites have shown remarkable performance as active layers in photovoltaic and other optoelectronic devices. However, their spin characteristic properties have not been fully studied, although due to the relatively large spin-orbit coupling these materials may show great promise for spintronic applications. Here we demonstrate spin-polarized carrier injection into methylammonium lead bromide films from metallic ferromagnetic electrodes in two spintronic-based devices: a ‘spin light emitting diode’ that results in circularly polarized electroluminescence emission; and a ‘vertical spin valve’ that shows giant magnetoresistance. In addition, we also apply a magnetic field perpendicular to the injected spins orientation for measuring the ‘Hanle effect’, from which we obtain a relatively long spin lifetime for the electrically injected carriers. Our measurements initiate the field of hybrid perovskites spin-related optoelectronic applications.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Optoelectronic devices incorporating fluoropolymer compositions for protection

The fluoropolymer compositions of the present invention generally incorporate ingredients comprising one or more fluoropolymers, an ultraviolet light protection component (hereinafter UV protection component), and optionally one or more additional ingredients if desired. The UV protection component includes a combination of at least one hindered tertiary amine (HTA) compound having a certain structure and a weight average molecular weight of at least 1000. This tertiary amine is used in combination with at least one organic, UV light absorbing compound (UVLA compound) having a weight average molecular weight greater than 500. When the HTA compound and the UVLA compound are selected according to principles of the present invention, the UV protection component provides fluoropolymer compositions with significantly improved weatherability characteristics for protecting underlying materials, features, structures, components, and/or the like. In particular, fluoropolymer compositions incorporating the UV protection component of the present invention have unexpectedly improved ability to resist blackening, coloration, or other de gradation that may be caused by UV exposure. As a consequence, devices protected by these compositions would be expected to have dramatically improved service life. The compositions have a wide range of uses but are particularly useful for forming protective layers in optoelectronic devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2023

Ultrafast vibrational control of organohalide perovskite optoelectronic devices using vibrationally promoted electronic resonance

Vibrational control (VC) of photochemistry through the optical stimulation of structural dynamics is a nascent concept only recently demonstrated for model molecules in solution. Extending VC to state-of-the-art materials may lead to new applications and improved performance for optoelectronic devices. Metal halide perovskites are promising targets for VC due to their mechanical softness and the rich array of vibrational motions of both their inorganic and organic sublattices. Here, we demonstrate the ultrafast VC of FAPbBr 3 perovskite solar cells via intramolecular vibrations of the formamidinium cation using spectroscopic techniques based on vibrationally promoted electronic resonance. The observed short (~300 fs) time window of VC highlights the fast dynamics of coupling between the cation and inorganic sublattice. First-principles modelling reveals that this coupling is mediated by hydrogen bonds that modulate both lead halide lattice and electronic states. Cation dynamics modulating this coupling may suppress non-radiative recombination in perovskites, leading to photovoltaics with reduced voltage losses.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Highly Stable Transparent Conductive Electrodes Based on Silver–Platinum Alloy-walled Hollow Nanowires for Optoelectronic Devices

In industrial manufacturing, alloying can contribute to the passivation of active metals and markedly improve their corrosion resistance. This inspires us to solve the current critical problem of Ag nanowires (Ag NWs) that have poor stability against chemical and electrochemical corrosion. These problems have seriously limited the applications of Ag NWs in optoelectronic devices where they are used for transparent conductive electrodes. Here, a kind of transparent conductive electrode based on Ag@Pt alloy-walled hollow nanowires (Ag@Pt AHNWs) is successfully fabricated by introducing 12 mol% Pt into long Ag NWs to form Ag@Pt alloy. The as-synthesized electrodes exhibit better optical transmittance (82% at the wavelengthof 550 nm) under high electrical conductivity (28.73 O/sq), high thermal stability up to 400 oC for 11 h, remarkable mechanical flexibility (remaining stable after 5000 cycles bending), as well as high resistance against chemical and electrochemical corrosion. The Ag@Pt AHNWs electrodes are further applied in primary bifunctional polyaniline electrochemical device, and the device shows promising flexibility, noticeable multicolor performances and the high specific capacitance due to the remarkable mechanical flexibility and electrochemical stability of Ag@Pt AHNWs. This work will provide an optional approach for the preparation of other metal nanomaterials electrode with high stability.

Zhou, Kailin↗
DOE OSTI2022

Fabrication methods for high reflectance dielectric-metal point contact rear mirror for optoelectronic devices

The patterned dielectric back contact (PDBC) structure can be used to form a point-contact architecture that features a dielectric spacer with spatially distributed, reduced-area metal point contacts between the semiconductor back not recognized contact layer and the metal back contact. In this structure, the dielectric-metal region provides higher reflectance and is electrically insulating. Reduced-area metal point contacts provide electrical conduction for the back contact but typically have lower reflectance. The fabrication methods discussed in this article were developed for thermophotovoltaic cells, but they apply to any III-V optoelectronic device requiring the use of a conductive and highly reflective back contact. Patterned dielectric back contacts may be used for enhanced sub-bandgap reflectance, for enhanced photon recycling near the bandgap energy, or both depending on the optoelectronic application. The following fabrication methods are discussed in the article: PDBC fabrication procedures for spin-on dielectrics and commonly evaporated dielectrics to form the spacer layer; methods to selectively etch a parasitically absorbing back contact layer using metal point contacts as an etch mask; methods incorporating a dielectric etch through different process techniques such as reactive ion and wet etching.

14 SOLAR ENERGY↗
DOE OSTI2018

Significantly Enhanced Emission Stability of CsPbBr 3 Nanocrystals via Chemically Induced Fusion Growth for Optoelectronic Devices

Lead–halide perovskite nanocrystals (PNCs) have attracted much attention in recent years due to their outstanding optical properties. We report here a new chemical route for triggering postsynthetic growth of CsPbBr 3 PNCs at room temperature via intentional depletion of stabilizing ligands, resulting in an immediate fusion growth of the as-synthesized PNCs. Upon fusion, the CsPbBr 3 PNCs can grow from ca. 8 nm to ca. 60 nm in lateral dimensions in 48 h, reaching about 14 nm in thickness. More importantly, it was found that the fused PNCs have significantly enhanced optical properties. They showed an exceptionally higher stability to photodegradation. They also displayed sharper emission lines and a higher quantum yield, contrary to the fact that the nanocrystals are much larger. The much-improved optical properties are attributed to the Ruddlesden–Popper (RP) planar faults formed during the fusion process and observed using atomic resolution scanning transmission electron microscopy, which are predicted to result in quantum confinement based on density-functional theory calculations. The newly grown nanocrystals with RP defects are expected to significantly improve light emission properties of the PNCs and find applications in light-emitting diodes and other optoelectronic devices.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Ordered and Patterned Assembly of Organic Micro/Nanocrystals for Flexible Electronic and Optoelectronic Devices

Organic semiconductor micro/nanocrystals (OSMCs) have attracted intensive research over the past few decades. Their unique electrical and mechanical properties afford them applications in a vast network of active flexible electronic and optoelectronic fields, such as organic field‐effect transistors (OFETs), photodetectors (PDs), and organic light‐emitting diodes (OLEDs) etc. However, the growth orientation and location of OSMCs are usually stochastic in nature, which hinders the further use of OSMCs in large‐area plastic electronic devices. On the other hand, traditional microelectronic processing techniques like photolithography may damage the plastic substrates, polymer insulators, and organic materials. Thus the alignment and patterning of OSMCs and development of new device construction technologies are prerequisite for their flexible device applications in practice. In this progress report,the important advancement for fabricating the aligned and patterned OSMCs, with a focus on their applications in next‐generation flexible electronic and optoelectronic devices, is highlighted. Also, the challenges and outlooks of the ordered and patterned OSMCs in the flexible device applications are presented.

Deng, Wei↗
DOE OSTI2017

Fused thiophene-based conjugated polymers and their use in optoelectronic devices

The present teachings relate to polymeric compounds and their use as organic semiconductors in organic and hybrid optical, optoelectronic, and/or electronic devices such as photovoltaic cells, light emitting diodes, light emitting transistors, and field effect transistors. The disclosed compounds generally include as repeating units at least one annulated thienyl-vinylene-thienyl (TVT) unit and at least one other pi-conjugated unit. The annulated TVT unit can be represented by the formula: ##STR00001## where Cy.sup.1 and Cy.sup.2 can be a five- or six-membered carbocyclic ring. The annulated TVT unit can be optionally substituted at any available ring atom(s), and can be covalently linked to the other pi-conjugated unit via either the thiophene rings or the carbocyclic rings Cy.sup.1 and Cy.sup.2. The other pi-conjugated unit can be a conjugated linear linker including one or more unsaturated bonds, or a conjugated cyclic linker including one or more carbocyclic and/or heterocyclic rings.

36 MATERIALS SCIENCE↗
DOE OSTI2015

Fused thiophene-based conjugated polymers and their use in optoelectronic devices

The present teachings relate to certain polymeric compounds and their use as organic semiconductors in organic and hybrid optical, optoelectronic, and/or electronic devices such as photovoltaic cells, light emitting diodes, light emitting transistors, and field effect transistors. The disclosed compounds can provide improved device performance, for example, as measured by power conversion efficiency, fill factor, open circuit voltage, field-effect mobility, on/off current ratios, and/or air stability when used in photovoltaic cells or transistors. The disclosed compounds can have good solubility in common solvents enabling device fabrication via solution processes.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Conjugated polymers and their use in optoelectronic devices

The present invention relates to certain polymeric compounds and their use as organic semiconductors in organic and hybrid optical, optoelectronic, and/or electronic devices such as photovoltaic cells, light emitting diodes, light emitting transistors, and field effect transistors. The present compounds can provide improved device performance, for example, as measured by power conversion efficiency, fill factor, open circuit voltage, field-effect mobility, on/off current ratios, and/or air stability when used in photovoltaic cells or transistors. The present compounds can have good solubility in common solvents enabling device fabrication via solution processes.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Reduced Graphene Oxide–Cadmium Zinc Sulfide Nanocomposite with Controlled Band Gap for Large-Area Thin-Film Optoelectronic Device Application

Herein, we report the one pot single step solvothermal synthesis of reduced grapheme oxide–cadmium zinc sulfide (RGO–Cd{sub 0.5}Zn{sub 0.5}S) composite. The reduction in graphene oxide (GO), synthesis of Cd{sub 0.5}Zn{sub 0.5}S (mentioned as CdZnS in the text) nanorod and decoration of CdZnS nanorods onto RGO sheet were done simultaneously. The structural, morphological and optical properties were studied thoroughly by different techniques, such as XRD, TEM, UV–Vis and PL. The PL intensity of CdZnS nanorods quenches significantly after the attachment of RGO, which confirms photoinduced charge transformation from CdZnS nanorods to RGO sheet through the interface of RGO–CdZnS. An excellent photocurrent generation in RGO–CdZnS thin-film device has been observed under simulated solar light irradiation. The photocurrent as well as photosensitivity increases linearly with the solar light intensity for all the composites. Our study establishes that the synergistic effect of RGO and CdZnS in the composite is capable of getting promising applications in the field of optoelectronic devising.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

Development of “GaSb-on-silicon” metamorphic substrates for optoelectronic device growth

The epitaxial development and characterization of metamorphic “GaSb-on-silicon” buffers as substrates for antimonide devices is presented. The approach involves the growth of a spontaneously and fully relaxed GaSb metamorphic buffer in a primary epitaxial reactor, and use of the resulting “GaSb-on-silicon” wafer to grow subsequent layers in a secondary epitaxial reactor. The buffer growth involves four steps—silicon substrate preparation for oxide removal, nucleation of AlSb on silicon, growth of the GaSb buffer, and finally capping of the buffer to prevent oxidation. This approach on miscut silicon substrates leads to a buffer with negligible antiphase domain density. The growth of this buffer is based on inducing interfacial misfit dislocations between an AlSb nucleation layer and the underlying silicon substrate, which results in a fully relaxed GaSb buffer. A 1 μm thick GaSb layer buffer grown on silicon has ~9.2 × 10 7 dislocations/cm 2 . The complete lack of strain in the epitaxial structure allows subsequent growths to be accurately lattice matched, thus making the approach ideal for use as a substrate. Here we characterize the GaSb-on-silicon wafer using high-resolution x-ray diffraction and transmission electron microscopy. The concept’s feasibility is demonstrated by growing interband cascade light emitting devices on the GaSb-on-silicon wafer. The performance of the resulting LEDs on silicon approaches that of counterparts grown lattice matched on GaSb.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Synthesis and characterization thin films of conductive polymer (PANI) for optoelectronic device application

In this work we report preparation and investigation of structural and optical properties of polyaniline conducting polymer. By using sol-gel in spin coating technique to synthesize thin films of conducting polymer polyaniline (PANI). Conducting polymer polyaniline was synthesized by the chemical oxidative polymerization of aniline monomers. The thin films were characterized by technique: Hall effect, High Resolution X-ray diffraction (HR-XRD), Fourier transform infrared (FTIR) spectroscopy, Field emission scanning electron microscopy (FE-SEM), and UV-vis spectroscopy. Polyaniline conductive polymer exhibit amorphous nature as confirmed by HR-XRD. The presence of characteristic bonds of polyaniline was observed from FTIR spectroscopy technique. Electrical and optical properties revealed that (p-type) conductivity PANI with room temperature, the conductivity was 6.289×10{sup −5} (Ω.cm){sup −1}, with tow of absorption peak at 426,805 nm has been attributed due to quantized size of polyaniline conducting polymer.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Study on mechanically alloyed tin telluride screen-printed films for optoelectronic device applications

Narrow band gap semiconductor tin telluride (SnTe) was synthesized by mechanical alloying and its film was deposited on glass substrates by the economically and commercially feasible screen-printing technique. Deposition of the film was followed by sintering. Different analytical techniques were utilized to study the structure, surface morphology, elemental, optical and electrical characteristics of the film. X-ray diffraction analysis confirms that the film is polycrystalline in nature and exhibits rock salt type structure with preferred orientation of grains along (200) direction. EDAX spectrum confirms the presence of Sn and Te elements in the film. SEM image shows that the film exhibits uniform surface. The energy band gap of the film was determined by reflection spectra. The film is found to have a direct band gap of 0.37 eV. The dark electrical conductivity and activation energy of the film were measured in temperature range 300–380 K. Hall Effect measurement indicates that the film has p-type electrical conductivity.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2015

Preparation, characterization and electroluminescence studies of ZnO nanorods for optoelectronic device applications

In this work, ZnO nanorods were achieved by a simple chemical precipitation method in the presence of capping agent Poly Vinyl Pyrrolidone (PVP) at room temperature. X-Ray Diffraction (XRD) result indicates that the synthesized undoped ZnO nanorods have wurtzite hexagonal structure without any impurities. It has been seen that the growth orientation of the prepared ZnO nanorods were (101). XRD analysis revealed that the nanorods having the crystallite size 49 nm. The Scanning Electron Microscopy (SEM) image confirmed the size and shape of these nanorods. The diameter of nanorods has been found that 1.52 µm to 1.61 µm and the length of about 4.89 µm. It has also been found that at room temperature Ultra Violet Visible (UV-VIS) absorption band is around 355 nm (blue shifted as compared to bulk). Electroluminescence (EL) studies show that emission of light is possible at very small threshold voltage and increases rapidly with increasing applied voltage. It is seen that smaller ZnO nanoparticles give higher electroluminescence brightness starting at lower threshold voltage. The brightness is also affected by increasing the frequency of AC signal.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗