Effects of near-field photon tunneling on the performance of photon–enhanced thermionic emission energy conversion

2019 ◽  
Vol 222-223 ◽  
pp. 223-228 ◽  
Author(s):  
Xianglei Liu ◽  
Haifeng Xia ◽  
Yimin Xuan
Keyword(s):  
Energy Conversion ◽  
Near Field ◽  
Thermionic Emission ◽  
Emission Energy ◽  
Photon Tunneling

Simulation of Thermionic Emission From a Quantum Wire Using the Non-Equilibrium Green’s Function Method

2004 ◽  
Author(s):  
Yang Liu ◽  
Hassan Raza ◽  
Timothy S. Fisher
Keyword(s):  
Energy Conversion ◽  
Green’S Function ◽  
Work Function ◽  
Green's Function ◽  
Quantum Wire ◽  
Bulk Material ◽  
Thermionic Emission ◽  
Theoretical Development ◽  
Non Equilibrium Green’S Function ◽  
Non Equilibrium

Even though the theory of thermionic emission of electrons from bulk metals is well understood, discrete electron energy states exist when material length scales approach one nanometer, and the traditional treatment must be revised. This paper presents a theoretical development of thermionic emission from nanoscale materials. A general expression for the emitted current as a function of field, temperature and work function is established for a quantum wire. The results differ from those of 3-D bulk materials. Simulation of thermionic emission from a quantum wire is achieved with the non-equilibrium Green’s function (NEGF) method, which includes relevant mesocopic physics and has been widely applied to transport problems in nanostructures. The NEGF approach provides a powerful solution to modeling problems when interfacial transport effects between bulk and confined conductors are important. Both the theoretical and simulated results indicate a higher current density and thus higher energy conversion capacity than that of a bulk material with the same work function. Thus the quantum confined materials may provide a method for improving the capacity of direct energy conversion devices and systems.

Vacuum Thermionic Energy Conversion Based on Nanocrystalline Diamond Films

2006 ◽  
Vol 48 ◽  
pp. 83-92
Author(s):  
F.A.M. Koeck ◽  
J.M. Garguillo ◽  
John R. Smith ◽  
Y.J. Tang ◽  
G.L. Bilbro ◽  
...  
Keyword(s):  
Energy Conversion ◽  
Work Function ◽  
Diamond Films ◽  
Thermionic Emission ◽  
Nanocrystalline Diamond ◽  
Effective Work ◽  
Effective Work Function ◽  
Nanocrystalline Diamond Films ◽  
Thermionic Energy Conversion ◽  
Thermionic Energy

Vacuum thermionic energy conversion achieves direct conversion of heat into electrical energy. The process involves thermionic electron emission from a hot surface and collection of the electrons on a cold surface where the two surfaces are separated by a small vacuum gap. Results are presented which indicate that nanocrystalline diamond films could lead to highly efficient thermionic energy conversion at temperatures less that 700°C. A critical element of the process is obtaining a stable, low work function surface for thermionic emission. Results are presented which establish that N-doped diamond films with a negative electron affinity can exhibit a barrier to emission of less than 1.6 eV. Films can be deposited onto field enhancing structures to achieve an even lower effective work function. Alternatively, nanocrystalline diamond films prepared with S doping exhibit field enhanced thermionic emission and an effective work function of ~1.9 eV. The field enhanced structures can reduce the effect of space charge and allow a larger vacuum gap. The possibility of a low temperature nanocrystalline diamond based thermionic energy conversion system is presented.

scholarly journals Near-field thermophotovoltaic energy conversion using an intermediate transparent substrate

2018 ◽  
Vol 26 (2) ◽  
pp. A192 ◽  
Author(s):  
Takuya Inoue ◽  
Kohei Watanabe ◽  
Takashi Asano ◽  
Susumu Noda
Keyword(s):  
Energy Conversion ◽  
Near Field ◽  
Transparent Substrate

Solid-State and Vacuum Thermionic Energy Conversion

2005 ◽  
Vol 886 ◽  
Author(s):  
Ali Shakouri ◽  
Z. Bian ◽  
R. Singh ◽  
Y. Zhang ◽  
D. Vashaee ◽  
...  
Keyword(s):  
Thin Film ◽  
Power Generation ◽  
Solid State ◽  
Energy Conversion ◽  
Thermionic Emission ◽  
Hot Electron ◽  
Research Activities ◽  
Solid State Devices ◽  
Thermionic Energy Conversion ◽  
Thermionic Energy

ABSTRACTA brief overview of the research activities at the Thermionic Energy Conversion (TEC) Center is given. The goal is to achieve direct thermal to electric energy conversion with >20% efficiency and >1W/cm2 power density at a hot side temperature of 300–650C. Thermionic emission in both vacuum and solid-state devices is investigated. In the case of solid-state devices, hot electron filtering using heterostructure barriers is used to increase the thermoelectric power factor. In order to study electron transport above the barriers and lateral momentum conservation in thermionic emission process, the current-voltage characteristic of ballistic transistor structures is investigated. Embedded ErAs nanoparticles and metal/semiconductor multilayers are used to reduce the lattice thermal conductivity. Cross-plane thermoelectric properties and the effective ZT of the thin film are analyzed using the transient Harman technique. Integrated circuit fabrication techniques are used to transfer the n- and p-type thin films on AlN substrates and make power generation modules with hundreds of thin film elements. For vacuum devices, nitrogen-doped diamond and carbon nanotubes are studied for emitters. Sb-doped highly oriented diamond and low electron affinity AlGaN are investigated for collectors. Work functions below 1.6eV and vacuum thermionic power generation at temperatures below 700C have been demonstrated.

CO2 laser-induced thermionic emission from metals. Direct energy conversion

1969 ◽  
Vol 47 (21) ◽  
pp. 2419-2423 ◽  
Author(s):  
W. W. Duley
Keyword(s):  
Energy Conversion ◽  
Short Circuit ◽  
Thermionic Emission ◽  
Open Circuit ◽  
Incident Power ◽  
Direct Energy Conversion ◽  
Direct Energy ◽  
Open Circuit Voltages ◽  
Excitation Conditions ◽  
Short Circuit Currents

Electron emission has been observed when tungsten and molybdenum targets are subjected to focussed CO2 laser radiation. The characteristics of thermionic emission for a variety of excitation conditions are reported. The electron temperature is found to be [Formula: see text] for an incident power of 40 W cw. Direct energy conversion processes are discussed. Short circuit currents of 2–7 μA and open circuit voltages of 0.1–0.4 V have been observed.

Energy Transmission by Photon Tunneling in Multilayer Structures Including Negative Index Materials

2005 ◽  
Vol 127 (9) ◽  
pp. 1046-1052 ◽  
Author(s):  
C. J. Fu ◽  
Z. M. Zhang ◽  
D. B. Tanner
Keyword(s):  
Radiative Transfer ◽  
Near Field ◽  
Multilayer Structures ◽  
Negative Index ◽  
Material Loss ◽  
Surface Polaritons ◽  
Negative Index Materials ◽  
Photon Tunneling ◽  
Energy Conversion Devices ◽  
Positive Index

The phenomenon of photon tunneling, which depends on evanescent waves for radiative transfer, has important applications in microscale energy conversion devices and near-field optical microscopy. In recent years, there has been a surge of interest in the so-called negative index materials (NIMs), which have simultaneously negative electric permittivity and negative magnetic permeability. The present work investigates photon tunneling in multilayer structures consisting of positive index materials (PIMs) and NIMs. Some features, such as the enhancement of radiative transfer by the excitation of surface polaritons for both polarizations, are observed in the predicted transmittance spectra. The influence of the number of layers on the transmittance is also examined. The results suggest that the enhanced tunneling transmittance by polaritons also depends on the NIM layer thickness and that subdividing the PIM/NIM layers to enhance polariton coupling can reduce the effect of material loss on the tunneling transmittance.

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