Carrier Energy Filtering Effect Research Articles

Preparation and Characterization of Thermoelectric PEDOT/Te Nanorod Array Composite Films.

In this study, we prepared Te nanorod arrays via a galvanic displacement reaction (GDR) on a Si wafer, and their composite with poly(3,4-ethylenedioxythiophene) (PEDOT) were successfully synthesized by electrochemical polymerization with lithium perchlorate (LiClO4) as a counter ion. The thermoelectric performance of the composite film was optimized by adjusting the polymerization time. As a result, a maximum power factor (PF) of 235 µW/mK2 was obtained from a PEDOT/Te composite film electrochemically polymerized for 15 s at room temperature, which was 11.7 times higher than that of the PEDOT film, corresponding to a Seebeck coefficient (S) of 290 µV/K and electrical conductivity (σ) of 28 S/cm. This outstanding PF was due to the enhanced interface interaction and carrier energy filtering effect at the interfacial potential barrier between the PEDOT and Te nanorods. This study demonstrates that the combination of an inorganic Te nanorod array with electrodeposited PEDOT is a promising strategy for developing high-performance thermoelectric materials.

Effectively enhanced thermopower in polyaniline/Bi0.5Sb1.5Te3 nanoplate composites via carrier energy scattering

Carrier energy-filtering effect at organic–inorganic interface has been proved to be very effective for improving the performance of polymer-based thermoelectric composites. To introduce a large amount of organic–inorganic interfaces, Bi0.5Sb1.5Te3 nanoplates (BST NP) are fabricated and embedded into camphorsulfonic acid-doped polyaniline (CSA:PANI) through cryogenic grinding followed by hot pressing. It is found that BST NPs are dispersed uniformly in the matrix to form abundant hybrid interfaces in the CSA:PANI/BST NP composites, which shows great enhancement in Seebeck coefficient and power factor. The improvement can be attributed to energy-filtering effect at the CSA:PANI/BST NP interface, which is supported by the distinct transport behavior between CSA:PANI/BST NP and PANI/BST NP composites. Consequently, the maximum ZT values up to 8.637 × 10−4 at 300 K and 1.64 × 10−3 at 400 K are achieved, which is among the best thermoelectric performance of PANI-based bulk composites.

Enhanced thermoelectric performance via carrier energy filtering effect in β-Zn4Sb3 alloy bulk embedded with (Bi2Te3)0.2(Sb2Te3)0.8

In Pb-free β-Zn4Sb3 based composites incorporated with (Bi2Te3)0.2(Sb2Te3)0.8, we concurrently realize ∼30% increase in thermoelectric power factor through an energy filtering effect caused by carrier scattering at interface barriers, and ∼15% reduction in thermal conductivity due to interface scattering, allowing the figure of merit to reach 1.1 at 648 K in the composite system with 1 vol. % of (Bi2Te3)0.2(Sb2Te3)0.8.

Experimental evidence of enhancement of thermoelectric properties in tellurium nanoparticle-embedded bismuth antimony telluride

Abstract

Impact of In Situ Generated Ag2Te Nanoparticles on the Microstructure and Thermoelectric Properties of AgSbTe2 Compounds

A series of ternary (Ag2Te)x(Sb2Te3)100−x (x = 44 to 54) bulk materials with in situ generated Ag2Te nanoparticles were prepared from high-purity elements by combining the melt-quench technique with the spark plasma sintering technique. The influence of the Ag2Te nanoparticles on the thermoelectric transport properties, and the mechanism of nanoparticle formation were investigated. With increasing x, the concentration of the Ag2Te nanoparticles increased monotonically, but their diameter remained nearly unchanged. Due to the possible carrier energy filtering effect caused by the Ag2Te nanoparticle inclusions, the Seebeck coefficient of the sample with x = 50 was two times higher than that of the sample prepared by the melting method. Moreover, notable scattering of mid-to-long wavelength phonons arising from the evenly distributed Ag2Te nanoparticles led to a large reduction of the lattice thermal conductivity. All these effects led to the enhancement of the ZT value of the x = 50 sample (AgSbTe2) compared with the single-phase sample (x = 44).

Hole transport through single and double SiGe quantum dots

We report on measurements of hole transport through a double quantum dot structure formed by trench isolation from a SiGe:Si heterostructure. A period change in the Coulomb oscillations is observed upon changing a gate bias, which is attributed to the lowering of one of the tunnel barriers, effectively changing the device to a single quantum dot. Accompanying the period change is a significant change in the level of noise associated with the oscillations. This is explained by a carrier energy filtering effect in the double dot compared with the single dot, caused by the slight difference in energy level spacing in each quantum dot.