Thermoelectric generators (TEGs) convert heat directly into electricity. The devices are good at conducting electricity but poor at conducting heat, and they have a large thermopower (the ratio of the voltage to temperature difference across the device to its temperature difference).

The researchers, led by Muhammad Mustafa Hussain, began by fabricating their TEGs from the 2D layered materials bismuth telluride and antimony telluride on low-cost bulk mono-crystalline silicon. Next, they transformed the devices and the host silicon into flexible and transparent systems using state-of-the-art CMOS-compatible processes. The silicon layer is just 18 µm thick and contains 63 thermopiles.

“The TEGs we made generate 0.15 µW of power, which is 30 times more than previously-made devices of this kind,” Hussain told “The thin silicon contains trenches that serve to minimize heat loss from the hot end of the device to the cold end. The power generated by the finished device is enough to run ultralow power CMOS circuitry in sensors, including some in vivo biomedical devices.”

The 30% increase in power output comes thanks to the reduced cross-sectional area of the silicon substrate and the fact that it is very flexible, explains team member Galo Torres Sevilla. The mechanical flexibility also greatly increases the number of potential applications for this type of device, he says, since the platform can be integrated onto a wide variety of surfaces, even irregularly shaped ones.

“We believe that the number of applications for these TEGs are virtually unlimited, ranging from consumer electronics such as cellphones, laptops and portable devices to systems that need to be used in hostile and difficult-to-access locations,” added Hussain. “The devices might be particularly suitable for implantable and wearable electronics, and they may even help overcome difficulties inherent in such applications, like reduced lifetime because of battery failure.”

The team now plans to fabricate a flexible, high-performance, self-powering system on a chip based on its TEGs. “The main challenge here will be to integrate all the different electronic modules, power generation and storage in a single structure,” explained Hussain. “However, we are confident that we will be able to make such a standalone system in the near future.”

The current research is detailed in Small DOI: 10.1002/smll.201301025.

Further reading

Nanoparticles boost thermoelectric efficiency (Jan 2011)
Thermoelectrics go nano (May 2008)
Nanostructuring boosts thermoelectric power in semiconductor layers (Oct 2009)
(Oct 2012)