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Title: Bilayer graphene phonovoltaic-FET: In situ phonon recycling

Abstract

A new heat harvester, the phonovoltaic (pV) cell, was recently proposed. The device converts optical phonons into power before they become heat. Due to the low entropy of a typical hot optical phonon population, the phonovoltaic can operate at high fractions of the Carnot limit and harvest heat more efficiently than conventional heat harvesting technologies such as the thermoelectric generator. Previously, the optical phonon source was presumed to produce optical phonons with a single polarization and momentum. Here, we examine a realistic optical phonon source in a potential pV application and the effects this has on pV operation. Supplementing this work is our investigation of bilayer graphene as a new pV material. Our ab initio calculations show that bilayer graphene has a figure of merit exceeding 0.9, well above previously investigated materials. This allows a room-temperature pV to recycle 65% of a highly nonequilibrium, minimum entropy population of phonons. However, full-band Monte Carlo simulations of the electron and phonon dynamics in a bilayer graphene field-effect transistor (FET) show that the optical phonons emitted by field-accelerated electrons can only be recycled in situ with an efficiency of 50%, and this efficiency falls as the field strength grows. Still, an appropriately designedmore » FET-pV can recycle the phonons produced therein in situ with a much higher efficiency than a thermoelectric generator can harvest heat produced by a FET ex situ.« less

Authors:
 [1];  [1]
  1. Univ. of Michigan, Ann Arbor, MI (United States). Dept. of Mechanical Engineering
Publication Date:
Research Org.:
Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). National Energy Research Scientific Computing Center (NERSC)
Sponsoring Org.:
USDOE Office of Science (SC)
OSTI Identifier:
1544352
DOE Contract Number:  
AC02-05CH11231
Resource Type:
Journal Article
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 96; Journal Issue: 20; Journal ID: ISSN 2469-9950
Publisher:
American Physical Society (APS)
Country of Publication:
United States
Language:
English

Citation Formats

Melnick, Corey, and Kaviany, Massoud. Bilayer graphene phonovoltaic-FET: In situ phonon recycling. United States: N. p., 2017. Web. doi:10.1103/PhysRevB.96.205444.
Melnick, Corey, & Kaviany, Massoud. Bilayer graphene phonovoltaic-FET: In situ phonon recycling. United States. doi:10.1103/PhysRevB.96.205444.
Melnick, Corey, and Kaviany, Massoud. Wed . "Bilayer graphene phonovoltaic-FET: In situ phonon recycling". United States. doi:10.1103/PhysRevB.96.205444.
@article{osti_1544352,
title = {Bilayer graphene phonovoltaic-FET: In situ phonon recycling},
author = {Melnick, Corey and Kaviany, Massoud},
abstractNote = {A new heat harvester, the phonovoltaic (pV) cell, was recently proposed. The device converts optical phonons into power before they become heat. Due to the low entropy of a typical hot optical phonon population, the phonovoltaic can operate at high fractions of the Carnot limit and harvest heat more efficiently than conventional heat harvesting technologies such as the thermoelectric generator. Previously, the optical phonon source was presumed to produce optical phonons with a single polarization and momentum. Here, we examine a realistic optical phonon source in a potential pV application and the effects this has on pV operation. Supplementing this work is our investigation of bilayer graphene as a new pV material. Our ab initio calculations show that bilayer graphene has a figure of merit exceeding 0.9, well above previously investigated materials. This allows a room-temperature pV to recycle 65% of a highly nonequilibrium, minimum entropy population of phonons. However, full-band Monte Carlo simulations of the electron and phonon dynamics in a bilayer graphene field-effect transistor (FET) show that the optical phonons emitted by field-accelerated electrons can only be recycled in situ with an efficiency of 50%, and this efficiency falls as the field strength grows. Still, an appropriately designed FET-pV can recycle the phonons produced therein in situ with a much higher efficiency than a thermoelectric generator can harvest heat produced by a FET ex situ.},
doi = {10.1103/PhysRevB.96.205444},
journal = {Physical Review B},
issn = {2469-9950},
number = 20,
volume = 96,
place = {United States},
year = {2017},
month = {11}
}

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