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Sustainable thermionic emission in CO2, helium and argon surroundings
摘要： Thermionic materials are commonly used in high vacuum (< 10?5 mbar). We measured thermionic emission of different doped metal-oxides cathodes – Zr doped Gd2O3 and Nb doped SrTiO3 (1 1 1) – in a CO2 surrounding, at T = 1300 °C and ～10?4 mbar ≤ p ≤ 300 mbar. Experimental setup validation and reference data were provided by measurements using cathodes made of CeB6, a commercial thermionic material, and by using either helium or argon as the surrounding gas. The study’s results could be used when examining enhancement of CO2 reduction to CO using vibration’s excitation. The thermionic emission of all cathodes decreased gradually as the pressure increased, as expected, but the exposure to CO2 did not cause a deterioration of the Zr doped Gd2O3 cathodes. They retained a reasonable emission, of ～60% and ～40% of the current in vacuum, at a CO2 pressure of 50 mbar and 300 mbar, respectively, over 20 operation hours. The data suggest that in the presence of significant gas pressure in the cathodes surrounding, the electric dipole of CO2 molecules and the cathode’s surface roughness may induce several mechanisms, which could affect the current emission.
关键词： Surface,CO2 helium argon,CO2 reduction,Thermionic emission
更新于2025-09-23 15:22:29
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Current transport mechanism of Mg/Au ohmic contacts to lightly doped n-type <i>β</i> -Ga <sub/>2</sub> O <sub/>3</sub>
摘要： The carrier transport mechanism of Mg/Au ohmic contact for lightly doped β-Ga2O3 is investigated. An excellent ohmic contact has been achieved when the sample was annealed at 400 °C and the specific contact resistance is 4.3 × 10?4 Ω·cm2. For the annealed sample, the temperature dependence of specific contact resistance is studied in the range from 300 to 375 K. The specific contact resistance is decreased from 4.3 × 10?4 to 1.59 × 10?4 Ω·cm2 with an increase of test temperature. As combination with the judge of E00, the basic mechanism of current transport is dominant by thermionic emission theory. The effective barrier height between Mg/Au and β-Ga2O3 is evaluated to be 0.1 eV for annealed sample by fitting experimental data with thermionic emission model.
关键词： effective barrier height,beta-gallium oxide,Mg/Au,ohmic contact,thermionic emission theory
更新于2025-09-23 15:22:29
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Effect of thermal pre-treatment on thermionic emission current stability from carbon nanotube forests
摘要： Carbon nanotube forests have great potential as efficient thermionic electron emitters due to a highly localized optical heating effect (“Heat Trap”). In past experiments, we observed a rapid decay in the emission current. In this work, we demonstrate that a relatively stable emission current can be achieved if the nanotube forest is pre-heated to 300 °C for 4 hours priors to electron emission. We attribute this improved current stability to the removal of reactant species, such as water trapped within the nanotube forest network.
关键词： Heat Trap,outgassing,lifetime,Carbon nanotubes,current stability,cathode,thermionic emission
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Development of a Low-Work-Function Thermionic Cathode by Coating with LaB<inf>6</inf> and Carbide
摘要： A novel electron gun with lanthanum hexaboride (LaB6) thermionic cathodes with relatively low work functions is being developed by coating the metal surface with another material. When operated under thermionic emission mode, this tool provides both high brightness and high beam current simultaneously, has a long lifetime, and offers good stability during operation. Herein, we describe the basic design concept for a novel LaB6 cathode involving infiltration of a carbide solution. Moreover, we experimentally measured the thermionic-emission-mode work function of the rhenium surface modified with a LaB6 single-crystal powder and carbide solution.
关键词： work function,carbide solution,lanthanum hexaboride,thermionic emission
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - The structure of Scandium thin films on the W(100) surface observed using emission microscopy
摘要： Thermionic emission microscopy is used to observe scandium on W(100). Scandium thin films were deposited by thermal evaporation from a metal source onto W(100). The scandium films on W(100) were observed to de-wet from the W(100) surface and to form droplets when the surface is heated: the dewetting temperature is thickness dependent, and spans a range from 500 to 800 C, far below the melting temperature (1541 C). Thinner films produce smaller droplets.
关键词： thermionic,dewetting,scandium,emission,tungsten
更新于2025-09-23 15:21:21
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[IEEE 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - Kyoto, Japan (2018.7.9-2018.7.13)] 2018 31st International Vacuum Nanoelectronics Conference (IVNC) - The role of lateral confinement in the localized heating of thermionic emitters based on carbon nanotube forests
摘要： When vertically aligned carbon nanotube arrays (CNT forests) are heated by optical, electrical, or any other means, heat confinement (i.e. in perpendicular to the CNTs’ axes), which stems from the anisotropic structure of the forest, is expected to play an important role. It has been found that, in spite of being primarily conductive along the CNTs’ axes, focusing a laser beam on the sidewall of a CNT forest can lead to a highly localized hot region—an effect known as “Heat Trap”—and efficient thermionic emission. This unusual heat confinement phenomenon has applications where the spread of heat has to be minimized, but electrical conduction in energy conversion (e.g. vacuum thermionics and thermoelectrics). However, despite its strong scientific and practical importance, the existence and role of the lateral heat confinement in the Heat Trap effect have so far been elusive. In this work, for the first time, by using a rotating elliptical laser beam, we directly observe the existence of lateral heat confinement and its corresponding effects on the unusual temperature rise during the Heat Trap effect.
关键词： lateral heat confinement,thermal anisotropicity,carbon nanotube forest,thermionic electron emitter,vacuum nanoelectronics,optical heating
更新于2025-09-23 15:21:21
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Photovoltaic anodes for enhanced thermionic energy conversion
摘要： Thermionic energy converters are heat engines based on the direct emission of electrons from a hot cathode towards a colder anode. Since the thermionic emission is unavoidably accompanied by photonic emission, radiative energy transfer is a significant source of losses in these devices. In this letter, we provide the experimental demonstration of a hybrid thermionic-photovoltaic device that is able to produce electricity not only from the electrons, but also from the photons that are emitted by the cathode. Thermionic electrons are injected in the valence band of a gallium arsenide semiconducting anode, then pumped to the conduction band by the photovoltaic effect, and finally extracted from the conduction band to produce useful energy before they are re-injected in the cathode. We show that such a hybrid device produces a voltage boost of ~ 1V with respect to a reference thermionic device made of the same materials and operating under the same conditions. This proof of concept paves the way to the development of efficient thermionic and photovoltaic devices for the direct conversion of heat into electricity.
关键词： thermionic energy conversion,photovoltaic,hybrid device,voltage boost,gallium arsenide
更新于2025-09-23 15:21:01
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Thermionic Emission-Based Interconnecting Layer Featuring Solvent Resistance for Monolithic Tandem Solar Cells with Solution-Processed Perovskites
摘要： All-perovskite tandem cells have been considered a potential candidate for bringing the power conversion efficiency (PCE) beyond the Shockley– Queisser limit of single-junction device while retaining the advantages of earth-abundant materials and solution processability. However, a challenging issue with regard to realizing such solution-processed devices is the fulfillment of complex and coupled requirements of the interconnecting layer (ICL), including solvent resistance to protect underlying perovskite film, high electrical properties for carrier transport and recombination, and high optical transmission. In this work, a new thermionic emission–based ICL with enhanced solvent resistance features is demonstrated. Fundamentally, the thermionic emission plays a critical role in the electron transport process in the ICL, which is confirmed through both experimental and theoretical studies. Besides achieving high optical transmission and electrical properties, the new ICL chemically protects the underlying perovskite film by introducing a fluoride silane– incorporated polyethylenimine ethoxylated hybrid system that also passivates the surface defects to reduce electrical loss. The monolithic all-perovskite tandem cells demonstrate highest PCE of 17.9% (from current density–voltage scan) and the highest steady-state efficiency is 16.1% for a typical device. Consequently, this work contributes to not only understanding the fundamental mechanism of ICLs but also promotes robust and low-cost photovoltaics.
关键词： monolithic all-perovskite tandem solar cells,solvent resistance,interconnecting layer,thermionic emission,defect passivation
更新于2025-09-23 15:21:01
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Selected methods of converting solar energy into electricity - comparative analysis
摘要： This article presents selected methods of converting solar energy into electricity: photovoltaic cells (PV), converters which use photon-enhanced thermionic emission (PETE), and near-field enhanced thermionic energy conversion systems (NETEC). PETE and NETEC systems are innovative solutions that use the thermionic emission phenomenon and can replace photovoltaic generation of electricity. We did a comparative analysis of such issues as: structure, principle of operation, - efficiency. working A comparison of these parameters is shown in the graphs and summarized in the table. Based on the analysis, we have drawn conclusions about previous achievements and development perspectives in the field of converting methods.
关键词： solar energy,PETE,NETEC,conversion efficiency,thermionic emission,photovoltaic cells
更新于2025-09-23 15:21:01
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[IEEE 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - New Delhi, India (2019.3.9-2019.3.15)] 2019 URSI Asia-Pacific Radio Science Conference (AP-RASC) - Generation of Pulsed Fiber Laser: ns to fs domain
摘要： Thermionic energy converter (TEC) is a heat engine that generates electricity directly using heat as its source of energy and electron as its working fluid. Despite having a huge potential as an efficient direct energy conversion device, the progress in vacuum-based thermionic energy converter development has always been hindered by the space charge problem and the unavailability of materials with low work function. It is only recently that researchers have started to look back into this technology as recent advances in manufacturing technology techniques have made it possible to solve these problems, making TECs a viable option in replacing current energy production systems. The focus of this paper is to review the challenges of producing efficient and practical TECs, along with recent findings and developments in mitigating these challenges. Furthermore, this paper looked into potential applications of TECs, based on recent works and technologies, and found that, with certain improvements, it can be applied in many sectors.
关键词： nanowires,work function,thermionic energy conversion (TEC),space charge,Energy conversion efficiency
更新于2025-09-23 15:19:57