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Title: Back-gated graphene anode for more efficient thermionic energy converters

Journal Article · · Nano Energy
 [1];  [1];  [2];  [3];  [4];  [5]
  1. Stanford Univ., Stanford, CA (United States)
  2. Stanford Univ., Stanford, CA (United States); Dept. of Applied Physics, Stanford, CA (United States)
  3. Dept. of Electrical Engineering, CA (United States); SLAC National Accelerator Lab., Menlo Park, CA (United States)
  4. Dept. of Material Science and Engineering, Stanford, CA (United States)
  5. Dept. of Electrical Engineering, CA (United States)
+ Show Author Affiliations

Thermionic energy converters (TECs) are a direct heat-to-electricity conversion technology with great potential for high efficiency and scalability. However, space charge barrier in the inter-electrode gap and high anode work function are major obstacles toward realizing high efficiency. Here, we demonstrate for the first time a prototype TEC using a back-gated graphene anode, a barium dispenser cathode, and a controllable inter-electrode gap as small as 17 µm, which simultaneously addresses these two obstacles. This leads to an electronic conversion efficiency of 9.8% at cathode temperature of 1000 °C, the highest reported by far. We first demonstrate that electrostatic gating of graphene by a 20 nm HfO2 dielectric layer changes the graphene anode work function by 0.63 eV, as observed from the current-voltage characteristics of the TEC. Next, we show that the efficiency increases by a factor of 30.6 by reducing the gap from 1 mm down to 17 µm, after a mono-layer of Ba is deposited on graphene by the dispenser cathode. Lastlu, we show that electrostatic gating of graphene further reduces the graphene work function from 1.85 to 1.69 eV, leading to an additional 67% enhancement in TEC efficiency. Note that the overall efficiency using the back-gated graphene anode is 6.7 times higher compared with that of a TEC with a tungsten anode and the same inter-electrode gap.

Research Organization:
SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States)
Sponsoring Organization:
USDOE
Grant/Contract Number:
Howe ICLFY11-01; AC02-76SF00515
OSTI ID:
1353107
Journal Information:
Nano Energy, Vol. 32, Issue C; ISSN 2211-2855
Publisher:
ElsevierCopyright Statement
Country of Publication:
United States
Language:
English
Citation Metrics:
Cited by: 45 works
Citation information provided by
Web of Science

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Solar Thermionic-Thermoelectric Generator (ST 2 G): Concept, Materials Engineering, and Prototype Demonstration journal October 2018
Generalized High-Energy Thermionic Electron Injection at Graphene Interface journal July 2019
Performance improvements and parametric design strategies of an updated thermionic-photovoltaic converter journal February 2020
Using a multi-layer graphene-based emitter to improve the performance of a concentrated solar thermionic converter journal October 2018
Nano-size effects in graphite/graphene structure exposed to cesium vapor journal September 2018
Near-field thermionic-thermophotovoltaic energy converters journal May 2019
Optimal performance region of energy selective electron cooling devices consisting of three reservoirs journal June 2019
Generalized high-energy thermionic electron injection at graphene interface text January 2019

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Related Subjects

75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
30 DIRECT ENERGY CONVERSION
Thermionic energy converter
Graphene
Electrostatic gating
Space charge barrier
Work function