Abstracts Book - IMRC 2018

• SC6-O014 Invited Talk
THERMAL RADIATION AT THE WAVELENGTH SCALE AND
THERMOPHOTOVOLTAICS
Pierre-Olivier Chapuis 1 , Etienne Blandre 2 , Khac Long Nguyen 2 , Yoichiro Tsurimaki 3,4 , Christophe
Lucchesi 5 , Makoto Shimizu 4 , Olivier Merchiers 2 , Rodolphe Vaillon 6,7
1 CNRS, CETHIL (Centre for Energy and Thermal Sciences), France. 2 CETHIL - INSA Lyon, CETHIL,
France. 3 CETHIL - INSA Lyon, , France. 4 Tohoku University, Department of Mechanical
Engineering, Japan. 5 CETHIL - CNRS, CETHIL, France. 6 CNRS, CETHIL, France. 7 IES Madrid, IES,
Spain.
In this talk we discuss different topics related to thermal radiation at the
wavelength scale and its application to thermophotovoltaics.
We first analyze in detail how macroscopic thermal radiation ceases to be valid
in the micrometric regime. The case of the parallel surfaces at two different
temperatures, which involves first a weak coherent regime before the strong
near-field increase, shows that the usual estimate of the characteristic interbody
distance based on Wien’s law (10 micrometers at room temperature)
underestimates the actual distance [1]. Similarly, we show that thermal emission
by spheres deviates already significantly the macroscopic prediction for radii
larger than 150 micrometers [2]. The maximal far-field emission is achieved by
means of coherent effects, similarly to the case of thin films [3,4]. In all cases,
the temperature dependence of the dielectric function affects the radiative
transfer [1-4]: the transferred power can depart strongly the usual fourth power
of temperature given by Planck’s law and the square or the cube of the object
size expected for surface or volume emission. These effects can be observed
partially in scanning thermal microscopy experiments, which can now be
modelled despite their non-academic geometry [5].
In a second part, we apply this knowledge to 1D multilayer structures for
thermophotovoltaic (TPV) applications [6]. Near-field TPV devices are expected
to provide larger electrical outputs than far-field devices due to the additional
energy transferred to the photovoltaic cell by evanescent waves. However, they
require also accurate modelling due to the large electron-hole pair density
generation [6]. We discuss architectures for near-field absorption and their
impacts.
Reference:
[1] Y. Tsurimaki, P.-O.Chapuis, J. Okajima, A.Komiya, S. Maruyama, R. Vaillon,
JQSRT 187, 310 (2017)