(470c) Molecular and Hybrid Solution Processible Thermoelectrics

Yee, S., University of California at Berkeley

Thermoelectric materials for energy generation have several
advantages over conventional power cycles including lack of moving parts,
silent operation, miniaturizability, and CO2 free
conversion of heat to electricity. Excellent
thermoelectric efficiency requires a combination of high thermopower
(S, V/K), high electrical conductivity (σ, S/cm), and low thermal
conductivity (κ, W/mK).  To date the best
materials available have been inorganic compounds with relatively low earth
abundance and highly complex, vacuum processing routes (and hence greater
expense), such as Bi2Te3. Molecular materials and
hybrid organic-inorganics bring the promise of
inexpensive, solution processible, mechanically
durable devices.  While highly
conductive polymers are now common place, they
generally demonstrate low thermopower. Our work on
molecular scale junctions demonstrates that nanostructuring
of organics allows them to act as thermionic filters between inorganic
junctions which can lead to enhanced thermoelectric properties. We have taken
inspiration from this fundamental understanding to design material systems in
which we combine a high electrical conductivity, low thermal conductivity
polymer with a nanoparticle that contributes high thermopower. 
Additionally, the work functions of the two materials are well-aligned which introduces the possibility of thermionic
filtering at the interface and an additional boost to the power factor.   The combination of these effects results in a new hybrid,
solution processible material with a thermoelectric
figure of merit within an order of magnitude of the Bi2Te3.   In this talk, I will discuss both the use of
thermoelectric measurements to gain insight to molecular junctions and how this
insight translates to design principles for polymer and hybrid thermoelectrics.