Durable Dense Packed All‐Silicon Micro‐Thermoelectric Generator for IoT Applications

Abstract

One of the main challenges of the rising field of the Internet of Things (IoT) is the self‐sustainable supply of energy to the sensors. Among the available environmental sources, heat can be harvested by means of thermoelectric devices. This work presents a new generation of densely packaged all‐silicon micro‐thermoelectric generators (µTEGs) with planar architecture. Optimized boron‐doped Si nanowires with 80 ± 30nm in diameter are epitaxially integrated as dense arrays into these generators for an improved performance. A procedure to reliably place a heat sink on top of the devices, enlarging the fraction of external thermal gradient captured by the thermoelectrically active nanowires, is described. These improvements enhance the generated voltage up to eight times with respect to that of a bare µTEG, leading to output powers well within the range of IoT needs (10 – 100 µW cm⁻²). Specifically, the µTEG on top of a heat source above 200°C and under still air convection conditions generates more than 14 µW cm⁻². When exposed to the same temperatures and to an airflow of 1.3 m s⁻¹ (equivalent to a light breeze) the power density increases above 150 µW cm⁻². Moreover, a long‐term stability study running the device in load matching conditions for a period of 1000 h does not show degradation below 200°C. Finally, the suitability of connecting the µTEG with the current state of the art DC–DC converters is discussed, showing how eventual transients in real operation conditions can allow the device to reach the required cold start‐up voltages. Overall, these results demonstrate the readiness of the presented µTEG as a reliable power source for miniaturized IoT applications.