BENGALURU: Researchers from the Department of Instrumentation and Applied Physics (IAP), Indian Institute of Science (IISc), along with other collaborators have designed a unique supercapacitor that can be charged by shining light on it. They can be used in various devices, including street lights and self-powered electronic devices such as sensors, said the research paper released on Thursday.
Capacitors are electrostatic devices that store energy as charges on two metal plates called electrodes. Super-capacitors are upgraded versions of capacitors – they exploit electrochemical phenomena to store more energy, said Abha Misra, IAP Professor and the co-author of the study. The research has also been published in the Journal of Materials Chemistry A. The electrodes of the supercapacitor are made of Zinc Oxide (ZnO) nanorods grown directly on Fluorine-doped Tin Oxide (FTO), which are transparent.
They were then synthesised. The two semi-conductors were then aligned to enhance the photo-recharging performance, explained Pankaj Singh Chauhan, co-author of the study paper and CV Raman postdoctoral fellow in Misra’s group at IISc. Chauhan added that since FTO is transparent, it allows light to fall on the optically active ZnO nanorods, which charge the supercapacitor.
When the researchers shined ultraviolet (UV) light on their supercapacitor, they noticed a huge increase in the capacitance, several times higher than previously reported supercapacitors. They also noticed two unusual properties. First, they found an increase in capacitance under light illumination with increasing voltage. This is called as necking behaviour, said AM Rao, Professor, Clemson University, USA, and co-author. Second, the team found that with the liquid electrolyte, the energy stored in the supercapacitor increased upon fast charging under UV light.
Mihir Parekh, a postdoctoral researcher in Rao’s group, developed theoretical models to explain these novel observations. To design their present supercapacitor, the team explored two key ideas. First, the surface area of the electrodes was increased by combining two optically active semiconductor interfaces in a way that maximises interaction with light, leading to higher charge generation. Second, a liquid electrolyte was used to ensure an effective electric double layer (EDL). Together, these resulted in superior performance, Misra said.