Thermoelectric modules based on polymers offer multiple advantages, including being printable, flexible, operating at moderate temperatures, and avoiding rare or toxic elements. They are also able to redistribute heat – a constant problem with current electronics.
But thermoelectric modules require semiconductor pairs to transport holes and electrons separately. Finding a suitable polymer for electron transport, or one which can be doped in order to make it suitable, is a challenge.
Researchers from the USA have now fabricated a purely n-type polymer semiconductor composite for electron transport. They combine a pyromellitic diimide polymer which has pentafluorophenyl end caps with an in situ-crystallized inorganic component, SnCl2, chosen for its well-known reduction ability. This solid additive increases the electron-carrying capacity and the voltage that can be obtained from the temperature difference. The mechanism is a combination of electron donation to the polymer and surface electroni c effects.
They compare their polymer with current commercial polymer systems, and find that their voltage per unit temperature breaks the current record for n-type polymers.
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