Abstract
This paper presents in-plane bismuth-telluride-based thermoelectric (TE) energy generators fabricated using metal-shadow and radio-frequency sputtering methods at room temperature. The TE energy generators consist of four couples of 300-nm-thick nanostructured Bi2Te3 (n-BT) and Bi0.5Sb1.5Te3 (p-BST) thin films used as n-type and p-type materials, respectively, on a Si substrate for the p/n junctions of the TE energy generators. Furthermore, the effect of annealing treatment of both n-BT and p-BST thin films on the electrical and TE properties as well as the TE performance of the TE energy generators is discussed. By varying the temperature between the hot and cold junction legs of the n-BT/p-BST in-plane TE energy generators annealed at 200 °C, the maximum output voltage and power are determined to be ∼3.6 mV and ∼1.1 nW, respectively, at a temperature difference of 50 K. The output powers increased by ∼590% compared to that of the as-grown TE generator at a temperature difference of 90 K. This improvement in the TE performance is attributed to the enhancement of the electrical conductivity after heat treatment. From a numerical simulation conducted using a commercial software (COMSOL), we are confident that it plays a crucial role in determining the dimension (i.e., thickness of each leg) and material properties of both n-BT and p-BST materials of the in-plane TE energy generators.
Highlights
Thermoelectric (TE) energy generators have promising applications in the operation of smallscale electric devices and systems in microelectronics and wearable self-powered mobile electronics because they are ideal small-scale onboard power sources and they can directly produce a small amount of electrical power from any thermal energy source.[1,2] To utilize small-scale TE energy generators as micro-power source, their size must be significantly reduced by employing thin-film technology, as previously reported.[3]
The TE energy generators consist of four couples of nanostructured Bi2Te3 (n-BT) and Bi0.5Sb1.5Te3 (p-BST) thin films used as n-type and p-type materials on a Si substrate for p/n junction of the in-plane TE energy generators
Using the energy dispersive X-ray spectrometry (EDX) measurements (Fig. S1, supplementary material), we observed that the peaks of elements Bi and Te have an approximate ratio of 2:3, whereas the peaks of elements Bi, Sb, and Te have a ratio of 0.5:1.5:3, revealing the stoichiometry of p-BST film
Summary
TE energy generators have been achieved using various bulk materials.[3,7,10,11] Recently, studies have been conducted on nanoscale TE devices using a one-dimensional and two-dimensional nanostructure.[12,13,14] Among many TE materials, bismuth-telluride (Bi-Te) based compounds are considered the best candidates for use in thin-film-based TE devices to obtain high-performance TE energy generators working at a temperature below 400 K. We report in-plane bismuth-telluride-based TE energy generators fabricated using metal-shadow and radio-frequency (RF) sputtering method at room temperature. The TE energy generators consist of four couples of nanostructured Bi2Te3 (n-BT) and Bi0.5Sb1.5Te3 (p-BST) thin films used as n-type and p-type materials on a Si substrate for p/n junction of the in-plane TE energy generators. The effect of the annealing treatment of both n-BT and p-BST thin films on the TE performance of the in-plane TE energy generators is discussed
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