3 research outputs found
The Effects of the Size and the Doping Concentration on the Power Factor of n‑type Lead Telluride Nanocrystals for Thermoelectric Energy Conversion
For
the first time, we demonstrate a successful synthesis of colloidal
n-type lead telluride nanocrystals doped with iodine. By tuning the
reaction time and iodine concentration in the precursor solution,
nanocrystals with different sizes and doping concentrations are synthesized.
The Seebeck coefficient and electrical conductivity of the nanocrystals
are measured on nanocrystal thin films fabricated by dip-coating glass
substrates in the nanocrystals solution. Investigations on the influence
of size and doping concentration on the electrical properties have
been performed. The results show that the size of the nanocrystals
significantly influences the electrical conductivity but not the Seebeck
coefficient of nanocrystal films, while higher doping concentration
leads to lower Seebeck coefficient but higher electrical conductivity
in the nanocrystal films. Proof-of-concept thin-film thermoelectric
modules are also fabricated using both p-type and n-type PbTe nanocrystals
for the conversion of thermal energy into electrical energy
Structure and Thermoelectric Properties of Spark Plasma Sintered Ultrathin PbTe Nanowires
Solution-synthesized thermoelectric
nanostructured materials have
the potential to have lower cost and higher performance than materials
synthesized by solid-state methods. Herein we present the synthesis
of ultrathin PbTe nanowires, which are compressed by spark plasma
sintering at various temperatures in the range of 405–500 °C.
The resulting discs possess grains with sizes of 5–30 μm
as well as grains with sizes on the order of the original 12 nm diameter
PbTe nanowires. This micro- and nanostructure leads to a significantly
reduced thermal conductivity compared to bulk PbTe. Careful electron
transport analysis shows suppressed electrical conductivity due to
increased short-range and ionized defect scatterings, while the Seebeck
coefficient remains comparable to the bulk value. The PbTe nanowire
samples are found unintentionally p-type doped to hole concentrations
of 2.16–2.59 × 10<sup>18</sup> cm<sup>–3</sup>.
The maximum figure of merit achieved in the unintentionally doped
spark plasma sintered PbTe nanowires is 0.33 at 350 K, which is among
the highest reported for unintentionally doped PbTe at low temperatures
Electrochemical Effects in Thermoelectric Polymers
Conductive polymers such as PEDOT:PSS
hold great promise as flexible
thermoelectric devices. The thermoelectric power factor of PEDOT:PSS
is small relative to inorganic materials because the Seebeck coefficient
is small. Ion conducting materials have previously been demonstrated
to have very large Seebeck coefficients, and a major advantage of
polymers over inorganics is the high room temperature ionic conductivity.
Notably, PEDOT:PSS demonstrates a significant but short-term increase
in Seebeck coefficient which is attributed to a large ionic Seebeck
contribution. By controlling whether electrochemistry occurs at the
PEDOT:PSS/electrode interface, the duration of the ionic Seebeck enhancement
can be controlled, and a material can be designed with long-lived
ionic Seebeck enhancements