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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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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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Nanostructuring Confinement for Controllable Interfacial Charge Transfer
摘要： Carbon nanostructures supported semiconductors are common in photocatalytic and photoelectrochemical applications, as it is expected that the nanoconductors can improve the spatial separation and transport of photogenerated charge carriers. Transfer of charge carriers through the carbon-semiconductor interface is the key electronic process, which determines the role of charge separation channels, and is sensitively influenced by band structures of the semiconductor near the contacts. Usually, this electronic process suffers from excessive energy dissipation by thermionic emission, which will undesirably prevent the interfacial charge transfer and eventually aggravate the recombination of photogenerated charge carriers. Unfortunately, this critical issue has hardly been consciously considered. Here, ultrathin dopant-free tunneling interlayers coated on the surface of graphene and sandwiched between the carbon sheets and the semiconductor nanostructures are adopted as a model system to demonstrate energy saving for the interfacial charge transfer. The nanostructuring confinement of band bending within the ultrathin interlayers in contact with the graphene sheets effectively narrows the width of the potential barriers, which enables tunneling of a substantial number of photogenerated electrons to the co-catalysts without unduly consuming energy. Besides, the dopant-free tunneling interlayers simultaneously block the transferred electrons in the sandwiched graphene sheets from leakage.
关键词： nanostructuring confinement,thermionic emission,electron tunneling,charge transfer,charge transport
更新于2025-09-19 17:15:36
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Evaluating the performance of InGaN/GaN multi-quantum-well solar cells operated at elevated temperatures via DC and small-signal AC analysis
摘要： InGaN/GaN multi-quantum-well (MQW) solar cells are investigated with temperature-dependent DC and AC analysis, and the effects of differing QW number and thickness are determined. The carrier transport is shown to be dominated by thermionic emission rather than tunneling at elevated temperature but limited by recombination outside the depletion region. Temperature-dependent AC parameters of the III-N MQW devices in high-level injection are determined through a refined AC circuit model of the device. It is shown that the use of AC small-signal analysis and its ability to extract stored charge in the QWs, the comparison of built-in potential to VOC, and other solar cell critical values allows a device designer insight not possible via DC analysis alone. This critical data suggests that the number of QWs and total depletion volume needs to be matched to the operational temperature of a given high temperature solar cell.
关键词： AC circuit model,multi-quantum-well,solar cells,recombination,VOC,DC and AC analysis,depletion region,built-in potential,InGaN/GaN,thermionic emission,carrier transport,temperature-dependent
更新于2025-09-19 17:13:59
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Effect of Ag-doping on the structural, optical, electrical and photovoltaic properties of thermally evaporated Cadmium Selenide thin films
摘要： To study the capability of the CdSe thin films to use as an absorber layer in semi-transparent thin film solar cells, the structural, optical, electrical and photovoltaic properties of thermally evaporated CdSe thin films (thickness 300 nm) as a function of silver-doping were investigated. A novel and facile method was used to Ag-doping of the samples. Some aqueous solution of silver nitrate (with various concentration) was spin coated onto the surface of CdSe thin films followed by air-annealing to diffuse silver dopants into the layers. The field emission scanning electron microscope (FE-SEM) images showed that the surface of CdSe thin films was improved with our doping method. X-ray diffraction (XRD) analysis revealed the hexagonal structure of the samples. The crystallite size, micro-strain and dislocation density of CdSe thin films were evaluated using XRD patterns. The transmittance spectra in the wavelength range of 400–2500 nm were measured and then used to study other optical parameters. The optical energy band gap was decreased with Ag-doping from 1.96 eV to 1.67 eV. The electrical conductivity of FTO/CdSe:Ag/Al Schottky junction devices was improved by Ag-doping, and the photovoltaic efficiency was increased by Ag-doping form 1.53% for the undoped sample to 2.78% for the sample with the highest doping concentration. Obtained results show that Ag-doped CdSe thin films are a promising candidate to use as an absorber layer in semi-transparent solar cells and colorful photovoltaic windows.
关键词： semi-transparent solar cell,Ag-doping,CdSe thin films,Schottkty junction,Urbach energy,thermionic emission
更新于2025-09-16 10:30:52
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Schottky junction-based thermophotovoltaic-thermionic devices
摘要： The conceptual model of a Schottky junction-based thermophotovoltaic-thermionic device (SJTTD) that can simultaneously convert thermally emitted electrons and photons into electricity is proposed, where the cathode of the TIC and the anode/p-type silicon interface forms the SJ. The impacts of space charge effect (SCE) on the TIC and radiative recombination on the TPVC are taken into account. According to the theory of statistical physics, analytical expressions for the total power output density and energy conversion efficiency of the SJTTD are derived. The maximum power output density and efficiency are calculated numerically by optimizing the key parameters of the two subsystems. Further, the parametric optimum criteria are provided. The optimally operating states of the ideal and non-ideal SJTTDs are compared. The results show that selecting the cathode materials with high emissivity can significantly enhance the performance. The proposed model can be helpful for developing high-efficient hybrid electron devices.
关键词： Schottky junction,Optimum criterion,thermophotovoltaic,thermionic emission
更新于2025-09-11 14:15:04