Ultrahigh Thermoelectric Power Generation from Both Ion Diffusion by Temperature Fluctuation and Hole Accumulation by Temperature Gradient

Thermoelectric materials can be utilized to directly convert heat into electricity. This is particularly important for harvesting waste heat that is abundant on earth. But their thermoelectric performance is still not high enough for practical heat-to-electricity conversion after being studied for about 200 years. Instead of enhancing the figure of merit (ZT) of thermoelectric materials, a significant improvement in heat harvesting by constructing a hybrid ionic/electronic thermoelectric converter (HTEC) is demonstrated. The device consists of an electronic unit and an ionic unit. The electronic unit is made of a thermoelectric polymer, poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS), and the ionic unit is composed of an ionogel. In addition to the heat-to-electricity conversion by the electronic unit from a temperature gradient due to the Seebeck effect, the ionic unit can generate electricity from temperature fluctuations owing to thermal ionic diffusion (Soret effect). The power generation can be many times more than the control thermoelectric generator using PEDOT:PSS. Because the temperature of waste heat usually fluctuates, the HTECs can give rise to much higher heat-to-electricity power conversion than normal thermoelectric generators with electronic conductors only.