Wide-band receiver system development - Wide- band power multiplier
Circuit description and performance characteristics of frequency multiplier in wideband communications receiver system
RECEIVER↗
SEARCH · Search NASA
Results for “Wide band”
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.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Wide-Band, Wide-Scan Antenna For Circular Polarization
Circular polarization generated by linearly polarized elements. Basic two-by-two subarray of antenna elements made of microstrip patches. Patches arranged in orthogonal pattern. Fed through different phase shifters so signal at feed points have same orthogonal relationship in phase. Antennas of this general type useful in communications and phased-array radar.
Huang, John↗
Compositional Engineering for Efficient Wide Band Gap Perovskites with Improved Stability to Photoinduced Phase Segregation
Metal halide perovskites are attractive candidates for the wide band gap absorber in tandem solar cells. While their band gap can be tuned by partial halide substitution, mixed halide perovskites often have lower open-circuit voltage than would be expected and experience photoinduced trap formation caused by halide segregation. Here, we investigate solar cell performance and photostability across a compositional space of formamidinium (FA) and cesium (Cs) at the A-site at various halide compositions and show that using more Cs at the A-site rather than more Br at the X-site to raise band gap is more ideal as it improves both VOC and photostability. We develop band gap maps and design criteria for the selection of perovskite compositions within the Cs x FA 1–x Pb(Br y I 1–y ) 3 , space. With this, we identify perovskites with tandem-relevant band gaps of 1.68 and 1.75 eV that demonstrate high device efficiencies of 17.4 and 16.3%, respectively, and significantly improved photostability compared to that of the higher Br-containing compositions.
36 MATERIALS SCIENCE↗
Wide Band Gap Chalcogenide Semiconductors
Wide band gap semiconductors are essential for today’s electronic devices and energy applications because of their high optical transparency, controllable carrier concentration, and tunable electrical conductivity. The most intensively investigated wide band gap semiconductors are transparent conductive oxides (TCOs), such as tin-doped indium oxide (ITO) and amorphous In–Ga–Zn–O (IGZO), used in displays and solar cells, carbides (e.g., SiC) and nitrides (e.g., GaN) used in power electronics, and emerging halides (e.g., γ-CuI) and 2D electronic materials (e.g., graphene) used in various optoelectronic devices. Compared to these prominent materials families, chalcogen-based (Ch = S, Se, Te) wide band gap semiconductors are less heavily investigated but stand out because of their propensity for p-type doping, high mobilities, high valence band positions (i.e., low ionization potentials), and broad applications in electronic devices such as CdTe solar cells. This manuscript provides a review of wide band gap chalcogenide semiconductors. First, we outline general materials design parameters of high performing transparent semiconductors, as well as the theoretical and experimental underpinnings of the corresponding research methods. We proceed to summarize progress in wide band gap (EG > 2 eV) chalcogenide materials—namely, II–VI MCh binaries, CuMCh 2 chalcopyrites, Cu 3 MCh 4 sulvanites, mixed-anion layered CuMCh(O,F), and 2D materials—and discuss computational predictions of potential new candidates in this family, highlighting their optical and electrical properties. Then, we finally review applications—for example, photovoltaic and photoelectrochemical solar cells, transistors, and light emitting diodes—that employ wide band gap chalcogenides as either an active or passive layer. Overall, by examining, categorizing, and discussing prospective directions in wide band gap chalcogenides, this Review aims to inspire continued research on this emerging class of transparent semiconductors and thereby enable future innovations for optoelectronic devices.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Polarization-Induced Electrical Conductivity in Ultra-Wide Band Gap AlGaN Alloys.
Abstract not provided.
Armstrong, Andrew↗
Wide Band Gap CuGa(S,Se) 2 Thin Films on Transparent Conductive Fluorinated Tin Oxide Substrates as Photocathode Candidates for Tandem Water Splitting Devices
Theaim of this report was to explore the potential of CuGa(S,Se)2 thin films as wide-E G top cell absorbers for photoelectrochemical (PEC) water splitting. A synthesis was developed on fluorinated tin oxide (FTO) photocathodes by converting copper-rich co-evaporated CuGaSe2 into CuGa(S,Se)2 via a post-deposition annealing. We found it necessary to first anneal CuGaSe2 at low-temperature in sulfur then at high-temperature in nitrogen to preserve the transparency and conductivity of the FTO. Using this two-step synthesis, we fabricated a 1.72eV CuGa(S,Se) 2 photocathode with a saturation current density and photocurrent onset potential of 10mA/cm 2 and -0.20V vs. RHE, respectively. Yet we found that the PEC performance and sub-E G transmittance, worsened with increasing copper content. Using flatband potential measurements and the Gerischer model, we show that divergences in PEC performance of CuGa(S,Se) 2 photocathodes can be explained by differences in conduction band minimums and Fermi levels. We also explain that sub-E G transmittance is likely hampered by a defect band 100-400 meV below E C . Additional external quantum efficiency measurements of a high-efficiency 1.1 eV Cu(In,Ga)Se 2 photovoltaic driver, while shaded by the CuGa(S,Se) 2 photocathode, yielded a short-circuit current density of 4.14 mA/cm 2 revealing that CuGa(S,Se) 2 reflects promise as a top cell for PEC water splitting.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Wide band gap semiconductor NAND based neutron detection systems and methods
A wide band gap semiconductor NAND based neutron detection system includes a semiconductor layer comprising a wide band gap material with a neutron absorber material in the wide band gap material, and the semiconductor layer is the only layer of the wide band gap semiconductor NAND based neutron detection system fabricated with the neutron absorber material.
Preston, Jeffrey Robert↗
Narrow and wide band tunable absorbers based on gold squares dispersed in liquid crystal
In this paper, the absorption behavior of gold squares with different sizes has been investigated. Our study includes gold squares in two, three and four different sizes dispersed in liquid crystal to propose an absorber with post fabrication tunability. In this case, more than 95% narrow band as well as wide band absorptions have been obtained when two and three sizes of gold squares have been used. Moreover, wide band absorption spectrum with the full width at half maximum of about 0.31 µm has been obtained when there are four different sizes of gold squares in our structure. Also, graphene has been utilized to boost the narrow band absorption from about 80 to 95%.
77 NANOSCIENCE AND NANOTECHNOLOGY↗
Wide-Band Microwave Receivers Using Photonic Processing
In wide-band microwave receivers of a type now undergoing development, the incoming microwave signals are electronically preamplified, then frequency-up-converted to optical signals that are processed photonically before being detected. This approach differs from the traditional approach, in which incoming microwave signals are processed by purely electronic means. As used here, wide-band microwave receivers refers especially to receivers capable of reception at any frequency throughout the range from about 90 to about 300 GHz. The advantage expected to be gained by following the up-conversion-and-photonic-processing approach is the ability to overcome the limitations of currently available detectors and tunable local oscillators in the frequency range of interest. In a receiver following this approach (see figure), a preamplified incoming microwave signal is up-converted by the method described in the preceeding article. The frequency up-converter exploits the nonlinearity of the electromagnetic response of a whispering gallery mode (WGM) resonator made of LiNbO3. Up-conversion takes place by three-wave mixing in the resonator. The WGM resonator is designed and fabricated to function simultaneously as an electro-optical modulator and to exhibit resonance at the microwave and optical operating frequencies plus phase matching among the microwave and optical signals circulating in the resonator. The up-conversion is an efficient process, and the efficiency is enhanced by the combination of microwave and optical resonances. The up-converted signal is processed photonically by use of a tunable optical filter or local oscillator, and is then detected. Tunable optical filters can be made to be frequency agile and to exhibit high resonance quality factors (high Q values), thereby making it possible to utilize a variety of signal-processing modalities. Therefore, it is anticipated that when fully developed, receivers of this type will be compact and will be capable of both wide-band and narrowband signal processing. Thus, one compact receiver of this type would afford the functionality that, heretofore, could have been obtained only by use of multiple heterodyne microwave receivers.
Matsko, Andrey↗
Quasi-Wide-Band Laser
Quasi-Wide-Band (QWB) laser is first-time presented, whose gain-line-shape depends on the frequency-shift and line-broadening caused by temperature gradient and others. The self-mode-locking, ultra-low phase-noise amplification, and coherent beam combination of QWB laser are investigated.
Yingxin Bai↗
Triple-halide wide–band gap perovskites with suppressed phase segregation for efficient tandems
Wide–band gap metal halide perovskites are promising semiconductors to pair with silicon in tandem solar cells to pursue the goal of achieving power conversion efficiency (PCE) greater than 30% at low cost. However, wide–band gap perovskite solar cells have been fundamentally limited by photoinduced phase segregation and low open-circuit voltage. Here, we report efficient 1.67–electron volt wide–band gap perovskite top cells using triple-halide alloys (chlorine, bromine, iodine) to tailor the band gap and stabilize the semiconductor under illumination. We show a factor of 2 increase in photocarrier lifetime and charge-carrier mobility that resulted from enhancing the solubility of chlorine by replacing some of the iodine with bromine to shrink the lattice parameter. We observed a suppression of light-induced phase segregation in films even at 100-sun illumination intensity and less than 4% degradation in semitransparent top cells after 1000 hours of maximum power point (MPP) operation at 60°C. By integrating these top cells with silicon bottom cells, we achieved a PCE of 27% in two-terminal monolithic tandems with an area of 1 square centimeter.
14 SOLAR ENERGY↗
Double transition metal MXenes with wide band gaps and novel magnetic properties
Novel wide band gaps and magnetism in ordered titanium–vanadium, titanium–chromium, and titanium–manganese carbide and nitride based MXenes are predicted using density functional theory. Based on the recent synthesis of Ti centred double transition metal MXenes, we study MXenes with a central Ti layer and different surface early 3d metals, and various terminations, TiM 2 X 2 T (M = V, Cr, Mn; X = C, N; T = H, F, O, OH). While previously studied MXenes are strongly metallic, we predict surface metal and termination dependent metal–insulator transitions in the Cr–N and Mn–N series. A uniquely wide band gap over 1 eV is predicted for TiMn 2 N 2 F 2 using the HSE06 density functional while the unterminated TiMn 2 N 2 remains metallic. The entire TiCr 2 C 2 T series is predicted to be semiconducting. Distinct from the more common Ti–C MXenes, not all combinations of metals and terminations are predicted to be stable. Within the examined sets of materials, anti-ferromagnetic orders are generally most favorable. In conclusion, the new MXenes further extend the range of properties accessible in this family of two-dimensional nanomaterials.
36 MATERIALS SCIENCE↗
Thermal Conversion of Ultrathin Nickel Hydroxide for Wide Band Gap 2D Nickel Oxides
Wide band gap (WBG) semiconductors (E g > 2.0 eV) are integral to the advancement of next-generation electronics, optoelectronics, and power industries owing to their capability for high-temperature operation, high breakdown voltage, and efficient light emission. Enhanced power efficiency and functional performance can be attained through miniaturization, specifically via the integration of device fabrication into a two-dimensional (2D) structure enabled by WBG 2D semiconductors. However, as an essential subgroup of WBG semiconductors, 2D transition metal oxides (TMOs) remain largely underexplored in terms of physical properties and applications in 2D optoelectronic devices, primarily due to the scarcity of sufficiently large 2D crystals. Thus, our goal is to develop synthesis pathways for 2D TMOs possessing large crystal domains (e.g., >10 μm), expanding the 2D TMO family and providing insights for future engineering of 2D TMOs. Here, we demonstrate the synthesis of WBG 2D nickel oxide (NiO) (E g > 2.7 eV) thermally converted from 2D nickel hydroxide (Ni(OH) 2 ) with a lateral domain size larger than 10 μm. Moreover, the conversion process is investigated using various microscopic techniques, such as atomic force microscopy, Raman spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy, providing significant insights into morphology and structural variations under different oxidative conditions. The electronic structure of the converted Ni x O y is further investigated using multiple soft X-ray spectroscopies, such as X-ray absorption and emission spectroscopies.
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
Optimization of the design parameters for a wide-band radiometric system
The optimun design parameters for a swept frequency wide-band radiometric antenna system for spacecraft applications are studied. Wide band antenna systems are needed to observe layered surfaces which are frequency sensitive and require multiple measurements for interpretation. The lowest frequency band of interest is between 1.4 to 2.8 Ghz. Starting with a given size reflector fed in the offset mode by a corrugated horn located at the focus of the parabola, the primary performance indexes; e.g., half power beamwidth, cross polarization level, and overall beam efficiency were calculated over a wide frequency range (two to one) for different physical horn dimensions and for different values of f/D ratio. These data are used to find the best design under given restriction of reflector size and blockage.
Agrawal, P. K.↗
A wide-band fiber optic frequency distribution system employing thermally controlled phase compensation
An active wide-band fiber optic frequency distribution system employing a thermally controlled phase compensator to stabilize phase variations induced by environmental temperature changes is described. The distribution system utilizes bidirectional dual wavelength transmission to provide optical feedback of induced phase variations of 100 MHz signals propagating along the distribution cable. The phase compensation considered differs from earlier narrow-band phase compensation designs in that it uses a thermally controlled fiber delay coil rather than a VCO or phase modulation to compensate for induced phase variations. Two advantages of the wide-band system over earlier designs are (1) that it provides phase compensation for all transmitted frequencies, and (2) the compensation is applied after the optical interface rather than electronically ahead of it as in earlier schemes. Experimental results on the first prototype shows that the thermal stabilizer reduces phase variations and Allan deviation by a factor of forty over an equivalent uncompensated fiber optic distribution system.
Johnson, Dean↗
Wide Band Gap Chalcopyrite Photoelectrodes for Direct Water Splitting (Final Technical Report)
The chalcopyrite material class, typically identified by its most popular alloy CuInGaSe 2 , provides exceptionally good candidates for photoelectrochemical (PEC) water splitting and has the potential to meet DoE EERE’s targets in terms of hydrogen production costs (less than $2/gge). Some key advantages of this class include remarkable photon-to-electron conversion efficiency and a high Faradaic efficiency for the hydrogen evolution reaction, two characteristics essential for efficient PEC water splitting. However, the band gaps of commonly used chalcopyrites in the photovoltaic field (1.0-1.6 eV) are too narrow to be compatible with the multi-junction approach for efficient PEC hydrogen production, in which a stack of solar absorbers generates the bias required for water splitting. Nonetheless, previous studies performed by our team demonstrated that chalcopyrites’ narrow band gaps could be effectively widened using simple conversion steps, leading to functional chalcopyrite-based PEC electrodes with optical band gap in the 1.8-2.4 eV range, making this class highly suitable for renewable hydrogen production via water splitting. This multi-disciplinary research program lead by the University of Hawai’i/Hawai’i Natural Energy Institute combined unique analytical techniques (UNLV), state-of-the-art theoretical modeling (LLNL) with advanced thin film materials synthesis (HNEI, NREL and Stanford) to provide deeper understanding of wide band gap chalcopyrite-based PEC materials and engineer high performance/corrosion-resistant photocathodes with tunable energetics and compatible with the multi-junction approach. The goals of this project were to demonstrate photoelectrochemical (PEC) solar-hydrogen production using a dual absorber system with a solar-to-hydrogen conversion efficiency of at least 15% with an operational life up to 2,000 hours and capable of generating at least 3 liters of hydrogen in 8 hours. After a brief introduction (Section 1) and description of our work plan (Section 2), we present in Section 3 our results on the development of new wide bandgap copper chalcopyrites absorbers for PEC waters splitting. We first show through modeling how alloying can be used to tailor the optical properties and/or surface energetics of various material candidates. We also present how specific defects (e.g., GaCu) can lead to recombination centers within the forbidden gap of copper-poor chalcopyrites. Then, we present our efforts to synthesize high efficiency wide band gap CuGa 3 Se 5 , CuGa(S,Se) 2 and Cu(In,Ga)S 2 photocathodes capable of generating photocurrent density over 10 mA/cm 2 . We also demonstrate that Cu-rich absorbers should be avoided as they lead to poor sub-band gap optical transmission. In Section 4, we first report on our efforts to tune the energetics of chalcopyrites toward the hydrogen evolution reaction. First, we quantified the energetics of wide band gap chalcopyrites interfaced with conventional CdS buffer layer, as measured with X-ray photoelectron spectroscopy techniques, and evidence the presence of a large (and undesirable) conduction band offset at this interface. Then, we highlight some of the work performed with alternative buffer layers, including In 2 S 3 . Durability improvements with various ultra-thin protective layers are presented in Section 5. Our data show that TiO 2 combined with MoS 2 can significantly improve chalcopyrites lifetime up to 350 hours under continuous operation at 8 mA/cm 2 . Finally, in Section 6 we report strategies to integrate chalcopyrite photocathodes into standalone tandem PEC devices. Although promising methods were proposed for both mechanical and monolithic stacking with narrow band gap PV drivers, no functional device was fabricated on time to fulfill the program end goals.
08 HYDROGEN↗