Researchers from the Department of Instrumentation and Applied Physics (IAP), Indian Institute of Science (IISc) and collaborators have developed a novel supercapacitor that can be charged with light.
This innovation could be used in street lights and autonomous electronic devices, including sensors, since unlike standard capacitors, which store energy electrostatically, supercapacitors use electrochemical methods to retain significantly more energy, allowing them to “release charge more quickly than batteries,” explained Abha Misra, professor at the Department of Instrumentation and Applied Physics at IISc and an author of the study.
The supercapacitor’s electrodes are made of zinc oxide nanorods on a transparent substrate of fluorine-doped tin oxide, allowing light to pass through them and charge the device. When exposed to ultraviolet (UV) light, the supercapacitor demonstrated a large increase in capacitance – its ability to store electrical energy. “The ideas were simple… but when they were put together, they worked very well,” Misra adds.
Narrowing behavior
In addition to the impressive increase in capacity, the researchers discovered two unusual behaviors. First, the device's capacity increased with voltage under light exposure, a phenomenon co-author A.M. Rao of Clemson University refers to as “necking behavior.” Second, while energy storage typically decreases when charging is faster, the team found that their supercapacitor stored more energy during fast charging when exposed to UV light.
The research team used a liquid electrolyte to improve performance by enhancing the electrical double-layer effect, which plays a key role in the high energy storage capacity of supercapacitors. “We have miniaturized the supercapacitors to micrometer scale so that they can be integrated together with microelectronic chips,” says Misra, pointing to potential applications in mobile phones and other small devices.
Misra believes this new technology could eventually replace solar cells in streetlights due to its faster charging time and high energy density.
The research was published in Journal of Materials Chemistry Aand the team hopes to further develop the supercapacitor to charge it using visible and infrared light.
