A Flexible Micro‐Thermoelectric Generator Sticker with Trapezoidal‐Shaped Legs for Large Temperature Gradient and High‐Power Density

Micro‐thermoelectric generators (m‐TEGs) are considered one of the potential semi‐permanent power sources for portable self‐powered electronic devices. To supply a sufficient amount of power for applications, the m‐TEG needs high‐performance thermoelectric materials as well as a large temperature difference across the device. Here, an m‐TEG with a new device structure, fabricated with a thin polymer‐supporting layer and trapezoidal‐shaped thermoelectric legs is presented. The m‐TEG, in the form of a sticker, is also flexible and can be attached anywhere that requires power. An m‐TEG with a step height of 200 µm is fabricated by sputtering a (Bi, Te)‐based thermoelectric material, and the device structure is completed using various challenging device fabrication techniques. The thermoelectric legs in the resulting structure have a very small cross‐section area, which enables the m‐TEG to have a larger thermal resistance than the conventional structure. This allows creating a larger temperature gradient across the thermoelectric legs. The fabricated m‐TEG exhibits a temperature difference as large as 0.90 °C, and generates an excellent output power density of 14.37 nW cm −2 even under natural convection, when attached to a heat source of 48 °C.