Indian Institute of Science (IISc) researchers have designed a novel ultramicro supercapacitor, a tiny device capable of storing an enormous amount of electric charge.

IISc said that the ultramicro supercapacitor designed by the Department of Instrumentation and Applied Physics (IAP) apart from being small in size and more compact than existing supercapacitors can potentially be used in many devices ranging from streetlights to consumer electronics, electric cars and medical devices.

Storage issues

“Most of these devices are currently powered by batteries. However, over time, these batteries lose their ability to store charge and therefore have a limited shelf-life. Capacitors, on the other hand, can store electric charge for much longer, by virtue of their design. For example, a capacitor operating at 5 volts will continue to operate at the same voltage even after a decade. But unlike batteries, they cannot discharge energy constantly – to power a mobile phone, for example,” said the Insitute.

Supercapacitors, on the other hand, combine the best of both batteries and capacitors – they can store as well as release large amounts of energy, and are therefore highly sought-after for next-generation electronic devices.

In the current study, published in ACS Energy Letters, the researchers fabricated their supercapacitor using Field Effect Transistors or FETs as the charge collectors, instead of the metallic electrodes that are used in existing capacitors. “Using FET as an electrode for supercapacitors is something new for tuning charge in a capacitor,” said Abha Misra, Professor at IAP and corresponding author of the study.

Current capacitors

Current capacitors typically use metal oxide-based electrodes, but they are limited by poor electron mobility. Therefore, Misra and her team decided to build hybrid FETs consisting of alternating few-atoms-thick layers of molybdenum disulphide (MoS2) and graphene – to increase electron mobility – which are then connected to gold contacts.

In the future, the researchers are planning to explore if replacing MoS2 with other materials can increase the capacitance of their supercapacitor even more. They add that their supercapacitor is fully functional and can be deployed in energy-storage devices like electric car batteries or any miniaturised system by on-chip integration.