Thin-film thermoelectric devices with high room-temperature figures of merit

Abstract

Thermoelectric materials are of interest for applications as heat pumps and power generators. The performance of thermoelectric devices fs quantified by a figure of merit, ZT, where Z is a measure of a material's thermoelectric properties and Tis the absolute temperature A material with a figure of merit of around unity was first reported over four decades ago, but since then—despite investigation of various approaches—there has been only modest progress in frding materials with enhanced ZT values at room temperature Here we report thin-fihn thermoelectric materials that demonstrate a significant enhancement in ZT at 300 K, compared to state-of-the-art buk Bi2Te3alloys. This amounts to maximum observed factor of ∼ 2.4 for our p-type Bi2Te3/Sb2Te3superiattice devices. The enhancement is achieved by controling the transport of phonons and elections in the superiattices. Preliminary devices exhljit significant cooing (32Kat around room temperature) and the potential to pump a heat flux of up to 700 W cm −2;the localized cooing and heating occurs some 23,000 times faster than in buk devices. We anticipate that the combination of performance, power density and speed achieved in these materials wll lead to diverse technological appications: for example, in theimochemistry-on-a-chip, DMA microanays, fibre-optic switches and microelectrothermal systems.