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In view of the combinatorial approach to discovery of new thermoelectric materials,
it is highly desirable to have fast measurement techniques, if possible with capabilities to
access local fluctuations or gradients in material properties.
Using the generalized Planck& #39;s law of radiation [1] for fitting the photoluminescence
spectra is the most appropriate technique to access the quasi Fermi level splitting and the
temperature of the carriers in a semiconductor. These two parameters enable to determine
Seebeck coefficients for the material as a new photo-Seebeck effect [2].
The absolutely calibrated photoluminescence intensity profile[3] with the spatial
coordinates combined with Callen coupled transport equations and with the kinetic
expression of the transport parameters under the relaxation time approximation enable us
to determine: the Seebeck coefficient, the electrical conductivity, the thermal electron and
hole conductivity, the mobilities, the diffusion coefficients and the heat transferred from the
carriers to the lattice. All these parameters can be obtained either for electrons or for
holes[4], even simultaneously, for intrinsic semiconductor in ambipolar regime.
The method has been applied to a multi-quantum well structure of InGaAsP. Since
the luminescence comes from the wells, this method enables to access the transport
properties in the plane of the wells inside the whole structure. Since photoluminescence
does not require p-n junction nor high electrical conductivities for the measurement, this
optical contactless measurement technique of thermoelectrinc transport parameters
involving quasi-equilibrium carriers enables to access properties inside a given layer of the
whole structure or in materials with very low conductivities.
We will also show the perspectives offered for the research of new thermoelectric materials.
[1] Würfel, J. Phys. C : Solid State Phys., 1982
[2] Gibelli et al., Phys. Rev. Appl., 5 (2) 2016
Tauc, Czech J Phys, 1955
[3] Delamarre, Appl. Phys. Lett., 2012
[4] Gibelli et al., Physica B, October 2016
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