Abstract
The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. While nanocrystalline materials have already led to substantially higher thermoelectric efficiencies, further improvements are expected to arise from precise chemical engineering of nanoscale building blocks and interfaces. Here we present a simple and versatile bottom–up strategy based on the assembly of colloidal nanocrystals to produce consolidated yet nanostructured thermoelectric materials. In the case study on the PbS–Ag system, Ag nanodomains not only contribute to block phonon propagation, but also provide electrons to the PbS host semiconductor and reduce the PbS intergrain energy barriers for charge transport. Thus, PbS–Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial. Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K.
Highlights
The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal
The efficiency of thermoelectric devices is primarily governed by three interrelated material parameters: the electrical conductivity, s, the Seebeck coefficient or thermopower, S, and the thermal conductivity, k
Control of the chemical composition and crystallinity of thermoelectric materials at the nanoscale via engineering of multicomponent nanomaterials has proven to be effective for the reduction of thermal conductivity by promoting phonon scattering at grain boundaries[2,3,4,5,6,7]
Summary
The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. PbS–Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K. The goal of this configuration is to reach large charge carrier concentrations without deteriorating the mobility of charge carriers[12,13,14,15,16] In this three-dimensional (3D) modulation doping strategy[17,18,19,20], composition, size and distribution of semiconductor and metal nanodomains control the nanocomposite transport properties. The position of the quasi Fermi level relative to the conduction band of the semiconductor at the metal–semiconductor interface should be adjusted to align the bands and minimize scattering rates This can be done by selecting metallic nanocrystals of the appropriate material and size and adjusting their volume fraction. The simultaneous combination of high electrical conductivity, relatively large Seebeck coefficients, and reduced thermal conductivities provides thermoelectric figures of merit up to 1.7 at 850 K
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