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Electron Thermionic Emission from Graphene and a Thermionic Energy Converter

Shi-Jun Liang and L. K. Ang*

  • SUTD-MIT International Design Center, Singapore University of Technology and Design, Singapore 138682

  • *ricky_ang@sutd.edu.sg
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Phys. Rev. Applied 3, 014002 – Published 12 January, 2015

DOI: https://doi.org/10.1103/PhysRevApplied.3.014002

Abstract

In this paper, we propose a model to investigate the electron thermionic emission from single-layer graphene (ignoring the effects of the substrate) and to explore its application as the emitter of a thermionic energy converter (TIC). An analytical formula is derived, which is a function of the temperature, work function, and Fermi energy level. The formula is significantly different from the traditional Richardson-Dushman (RD) law for which it is independent of mass to account for the supply function of the electrons in the graphene behaving like massless fermion quasiparticles. By comparing with a recent experiment [K. Jiang et al., Nano Res. 7, 553 (2014)] measuring electron thermionic emission from suspended single-layer graphene, our model predicts that the intrinsic work function of single-layer graphene is about 4.514 eV with a Fermi energy level of 0.083 eV. For a given work function, a scaling of T3 is predicted, which is different from the traditional RD scaling of T2. If the work function of the graphene is lowered to 2.5–3 eV and the Fermi energy level is increased to 0.8–0.9 eV, it is possible to design a graphene-cathode-based TIC operating at around 900 K or lower, as compared with the metal-based cathode TIC (operating at about 1500 K). With a graphene-based cathode (work function=4.514  eV) at 900 K and a metallic-based anode (work function=2.5  eV) like LaB6 at 425 K, the efficiency of our proposed TIC is about 45%.

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Phys. Rev. Applied 3, 014002– Published 12 January, 2015
  • Received 19 May 2014

© 2015 American Physical Society

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