Quantum mechanics

Chemical physics

Materials science

Infrared

Thermal conductivity

Plasma

Thermoelectric effect

Seebeck coefficient

Thermoelectric materials

Polymer

Thermodynamics

Physics

Nanotechnology

Organic chemistry

Optics

Ambipolar diffusion

Composite material

Analytical Chemistry (journal)

Ionic bonding

Chemistry

Thermopile

Optoelectronics

Nature Communications

Measuring temperature and heat flux is important for regulating any physical, chemical, and biological processes. Traditional thermopiles can provide accurate and stable temperature reading but they are based on brittle inorganic materials with low Seebeck coefficient, and are difficult to manufacture over large areas. Recently, polymer electrolytes have been proposed for thermoelectric applications because of their giant ionic Seebeck coefficient, high flexibility and ease of manufacturing. However, the materials reported to date have positive Seebeck coefficients, hampering the design of ultra-sensitive ionic thermopiles. Here we report an "ambipolar" ionic polymer gel with giant negative ionic Seebeck coefficient. The latter can be tuned from negative to positive by adjusting the gel composition. We show that the ion-polymer matrix interaction is crucial to control the sign and magnitude of the ionic Seebeck coefficient. The ambipolar gel can be easily screen printed, enabling large-area device manufacturing at low cost.

Polymer gels with tunable ionic Seebeck coefficient for ultra-sensitive printed thermopiles