ABSTRACT
The aim of this chapter is to review briefly the thermoelectric properties of some organic materials
and to show that it is expected to find among them candidates that will have a higher thermoelectric
figure-of-merit than the existing inorganic materials. Although this possibility has already been
discussed in the literature,
information on the thermoelectric properties of organic materials is
sparse. Experimental values of the thermopower (Seebeck coefficient) a for some organic
semiconductors are collected in Table XIX of Ref. [5]. Although the absolute values of a vary in the
range from 0.002 to 2 mV/K, the electrical conductivity s is very small. Consequently the
thermoelectric figure-of-merit at temperature T, ZT ¼ ðsa
T=xÞ ,, 1; in spite of very low thermal
conductivity x: The electrical conductivity can be increased by doping, but is accompanied by a drastic
reduction in the thermopower. Recently, it was shown
that the thermoelectric power factor, P ¼ sa
;
for highly doped conjugated polymers tends to increase with the increase of s and that no saturation is
observed. The highest value P ¼ 20 mW/(cm K
) is obtained in polyacetylene doped with iodine,
which is one half that in Bi
Te
. The main problem is that this material ages and is unstable even in
inert atmosphere. In polyaniline films, values of ZT , 0.01 have been measured,
which are still very
far from the value of one for Bi
Te
. To the author’s knowledge, the highest value of ZT ¼ 0.15 at room
temperature was observed in polycopper phthalocyanine.
