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Flexible Thermoelectric Polymers and Systems. Группа авторовЧитать онлайн книгу.

Flexible Thermoelectric Polymers and Systems - Группа авторов


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Metal S (μV K−1) Semiconductor S (μV K−1) Flexible materials S (μV K−1)
Sb +47 Se +900 PEDOT:PSS +14–20
Mo +10 Te +500 PEDOT:Tso +30
Ag +6.5 Si +440 PA +10
Cu +6.5 Ge +300 PPy +10
Hg +0.6 Sb2Te3 +185 PANi +10–20
Pt +0.0 Pb3Ge39Se58 +1670 Poly(Ni‐ett) −125
Ni −15 Pb15Ge37Se58 −1990 graphene −10
Bi −72 Bi2Te3 −230 Carbon nanotube +20

      For degenerated semiconductors, the Seebeck coefficient is given by

      (1.6)upper S equals minus StartFraction pi squared k Subscript upper B Baseline upper T Over 3 e EndFraction left-bracket StartFraction d l n sigma left-parenthesis upper E right-parenthesis Over d upper E EndFraction right-bracket Subscript upper E equals upper E Sub Subscript normal upper F Subscript Baseline comma

      (1.7)sigma left-parenthesis upper E right-parenthesis equals e n left-parenthesis upper E right-parenthesis mu left-parenthesis upper E right-parenthesis comma

      where n(e) and μ(E) are the charge carrier density and mobility at energy E. Hence, a semiconductor with a large variation in the carrier density near the Fermi level can have a high Seebeck coefficient. This can be achieved by changing the band structure. This way to increase the Seebeck coefficient is called “band structure engineering”. In addition, the charge carrier density n(E) is related to the density of states (DOS), g(E),

      (1.8)n left-parenthesis upper E right-parenthesis equals g left-parenthesis upper E right-parenthesis f left-parenthesis upper E right-parenthesis period

      Thus, the Seebeck coefficient is related to the density of states near E F. Controlling the density of states can vary the Seebeck coefficient, and this is called “DOS engineering”.

      Another important formula is the dependence of the Seebeck coefficient on the difference between the average energy (E J) of the transporting electrons and the E F,

      (1.9)upper S equals minus StartFraction upper E Subscript normal upper J Baseline minus upper E Subscript normal upper F Baseline Over q upper T EndFraction comma

Schematic illustration of band structure of an n-type semiconductor. VB and CB are for the valence band and conduction band, respectively. The dots at the CB stand for electrons. Schematic illustration of dependence of the Seebeck coefficient, electrical conductivity, and power factor on the charge carrier concentration.
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