Integration of an electronic thermoelectric material with ionogels to harvest heat from both temperature gradient and temperature fluctuation

Thermoelectric materials based on the Seebeck effect can harvest heat only from temperature gradient, while waste heat can induce both temperature gradient and temperature fluctuation. Here, we demonstrate the high performance in heat-to-electricity harvesting by integrating the thin film of an inorganic thermoelectric material, Bi_0.4Sb_1.6Te₃, with an ionogel that has a high ionic thermovoltage due to the Soret effect. The hybrid inorganic-ionic thermoelectric converter composed of a Bi_0.4Sb_1.6Te₃ layer and an ionogel layer can generate power from both the temperature gradient via the Seebeck effect of Bi_0.4Sb_1.6Te₃ and the temperature fluctuation via the Soret effect of the ionogel. The overall performance of devices is related to the properties of the two layers, the interface between them, and the temperature gradient and fluctuation. Because of the additional heat harvesting from temperature fluctuation, this hybrid device can exhibit much higher performance in heat harvesting than the control thermoelectric generator (TEG) with the Bi_0.4Sb_1.6Te₃ layer alone, depending on the temperature fluctuation and humidity. The power performance of the hybrid converters can be higher than the TEG film by about 1/3 under temperature fluctuation at the relative humidity of 90%.