Traditional thermoelectric generators rely on temperature gradients to convert heat into electrical energy, where the temperature difference causes charge carriers to move from the hot side to the cold side, which generates electricity.
These generators produce greater energy at the more significant temperature gradients. However, this new device at Kyushu University extracts small-scale thermal energy, even at no temperature gradients.
As the world strives to be carbon emission-free, the shift towards renewable energy sources, especially thermoelectric devices, is gaining interest. However, traditional thermoelectric devices need regions at 100 °C or more in combination with cold areas, which limits their installations.
This new device works on the principle of Charge Separation. The charge separation here is achieved from the charge-bound state of charge transfer excitons using low thermal energy.
Charge transfer excitons are bound states of electrons and holes, and in this device, they are excited by room-temperature heat. Even low thermal energy is sufficient to separate electrons and holes. These electrons are then diffused and moved in opposing directions, which generates a current.
This device uses organic compounds like Copper phthalocyanine (CuPc) and F16CuPc. The foremost reason to not use inorganic is their toxicity. Inorganic compounds use rare earth metals, which adds to environmental concerns.
“We would like to continue working on this new device and see if we can optimize it further with different materials,” said Professor Chihaya Adachi, lead author of the study. “We can even likely achieve a higher current density if we increase the device’s area, which is unusual even for organic materials. It just goes to show you that organic materials hold amazing potential.”
The ability of the proposed device to generate energy from low thermal energy could revolutionize electric devices like wearables or computing chips. For instance, this material could allow wearables to charge from the body heat.
