Evaluation of energy filtering effect from first principles calculations

Abstract

Energy filtering effect is usually utilized in composites to enhance the thermoelectric performance, and a reliable theoretical approach is needed to predict the optimum parameters related to this effect. By taking Bi2Te3 as an example, we show that first principles calculations and Boltzmann transport equations can be used to evaluate energy filtering effect, and the optimal values for the maximum power factor of interfacial potential barrier height (Eb) and carrier scattering probability (p) can be calculated precisely. The calculation results show that the power factor can be greatly enhanced at high carrier concentrations by energy filtering. This enhancement is sensitive to Eb and p: to achieve 40% power factor enhancement, Eb must be in the range 0.06–0.10 eV, and p should be greater than 60%. The optimal Eb also shows weak dependence on p. Our approach can be easily applied to other materials due to the generality of first principles calculations, and will aid high throughput screening for new thermoelectric composites.

High Performance Thermoelectric Materials: Progress and Their Applications

“…By introducing potential barriers between grain boundaries, lower‐energy or minor charge carriers can be filtered, and the average carrier energy can be increased. As a consequence, S can be increased while σ will not be significantly reduced . The calculation results estimate significant improvement on S 2 σ when well‐designed potential barriers were introduced, while many experimental results confined that applying energy filters can effectively enhance the TE performance .…”

“…As a consequence, S can be increased while σ will not be significantly reduced . The calculation results estimate significant improvement on S 2 σ when well‐designed potential barriers were introduced, while many experimental results confined that applying energy filters can effectively enhance the TE performance . Figure d shows an example of the enhanced S 2 σ via energy filtering by manipulating grain boundaries of Yb‐filled CoSb 3 compared with its counterparts without energy filters.…”

“…According to the calculation results, [115] low-energy carriers negatively contribute to S (Figure 7c), while the carriers that have higher energy between www.advancedsciencenews.com 0.05 and 0.1 eV contribute the most for high S. [115] By introducing potential barriers between grain boundaries, lowerenergy or minor charge carriers can be filtered, [213] and the average carrier energy can be increased. [205,207,214] The calculation results estimate significant improvement on S 2 σ when well-designed potential barriers were introduced, [205] while many experimental results confined that applying energy filters can effectively enhance the TE performance. [205,207,214] The calculation results estimate significant improvement on S 2 σ when well-designed potential barriers were introduced, [205] while many experimental results confined that applying energy filters can effectively enhance the TE performance.…”

“…Another advantage of nanocomposite materials is the existence of the energy filtering effect: when there is a band offset between the host matrix and nanofillers, their boundaries can filter lower‐energy carriers ( Figure 7 a) or minor charge carriers (Figure b), as the energy filters . These can lead to the S increase since it depends strongly upon the carrier transport behavior of TE materials.…”

Polymer‐Based Low‐Temperature Thermoelectric Composites

“…One of the mechanisms to boost TE performance of the polymer composites is an energy filtering mechanism (EFM), [38,39], that is, the presence of an energy barrier at the phase interface of various compounds. The energy barrier is working as a "filter" system, where only charge carriers with enough energy can pass through, resulting in a decreased concentration of the charge carriers and in nominally increased entropy.…”