THERMOELECTRIC

MATERIALS

By

Vijitha I

Junior Research Fellow

CSIR-NIIST

PIONEER IN THERMOELECTRICS

Instrument used by Seebeck to observe the

deflection of a compass needle (a) due to a

thermoelectric induced current from heating

the junction of two different metals (n and o).

Thomas Seebeck

THERMOELECTRICITY

Temperature difference across a solid produces

thermally generated emf which can drive current

through a load (power generation)

Driving current through the same solid results in

heating in one contact and cooling in another

(refrigeration)

POWER GENERATION/ REFRIGERATION

THERMOELECTRIC EFFICIENCY

Thermoelectric Figure Of Merit

SEEBECK COEFFICIENT

Open circuit voltage produced per unit temperature

difference (Thermo EMF)

T

V

n

TK

EE

e

K

B

FCB

From transport calculations in nanoscale

THERMOELECTRIC MATERIALS

The good thermoelectric materials should possess

DESCRIPTION OF THE PROBLEM

Electron mobility is low for organic materials

Getting ZT for n-type and p-type TE materials at

same temperature

α σ

EC

EV

EF

N-type

α σ

TZT

α2

INTERRELATION

LTe

n

TK

EE

e

K

B

FCB

Wiedemann-Franz Law

Figure of merit

Seebeck coefficient

THE SWEET SPOT

Semiconductor

Semimetals &

highly doped

semiconductor

s

Metals

PROPOSED PLAN

Fabrication of hybrid materials

Understand underlying physics

Designing polymer composite based TE materials

and refrigeration modules

Roll-to-roll printable TE circuitries

Low power rating TE refrigerators compactable with

low cost organic solar cell

To be competitive, ZT should be ~ 0.5

APPLICATIONS OF TE MATERIALS

RTG

Thermoelectric converter moduleMars Science Laboratory

Thermoelectric generator