Organic-Inorganic Thermoelectric Material for a Printed Generator

Abstract

We made a thermoelectric mini-generator by a screen printing method. The sub-milliwatt electric power was generated on a heated plate at 60°C. The composite of Bi2Te3 particles and polyimide with ionic-liquid was made as an ink for printing. The printed composite film was annealed at 400 °C for 1 hour in Argon with hydrogen to improve the thermoelectric properties. The diameter of the Bi2Te3 particles was about 1-2 μm and polyimide with ionic-liquid was filled between the particles. The Seebeck coefficient of the film was measured by applying a temperature difference along the in-plane direction while measuring the Seebeck voltage. The electrical conductivity was measured by four-point probe method. The cross-plane thermal conductivity was measured by differential 3ω method. The measured Seebeck coefficient of p-type thermoelectric film was 245μV/K, the electrical conductivity was 160 S/cm, and the thermal conductivity was 0.33 W/(m • K). The Seebeck coefficient, the electrical conductivity and thermal conductivity for n-type was -165μV/K, 140 S/cm, and 0.23 W/(m•K), respectively. The non-dimentional figure of merit of the film is 0.87 for p-type, and 0.5 for n-type. Those thermoelectric properties were much improved than those of Bi2Te3 with PEDOT:PSS composite. The high thermoelectric properties are achieved by extremely low thermal conductivity of the composites. The thermal conductivities of both p-type and n-type films were lower than that of polyimide film.