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Researchers at the Indian Institute of Science (IISc) have designed a novel, tiny device capable of storing an enormous amount of electric charge. The ultra-micro supercapacitor is also much smaller and more compact than existing supercapacitors and can potentially be used in many devices ranging from streetlights to consumer electronics, electric cars and medical devices, according to Bengaluru-based IISc. 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, it said. Capacitors, on the other hand, can store electric charge for much longer, by virtue of their design. For example, a capacitor operating at five 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. 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 from IISc's Department of Instrumentation and Applied Physics (<keyword id="63950" type="General" weightage="80" keywordseo="iap" source="Orion">IAP</keyword>), 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 <keyword id="2298292" type="General" weightage="80" keywordseo="fet" source="Orion">FET</keyword> as an electrode for supercapacitors is something new for tuning charge in a capacitor," <keyword id="17005548" type="General" weightage="80" keywordseo="abha-misra" source="Orion">Abha Misra</keyword>, Professor at IAP and corresponding author of the study, was quoted as saying in an IISc statement issued on Friday. Current capacitors typically use metal oxide-based electrodes, but they are limited by poor electron mobility. Therefore, <keyword id="121202" type="General" weightage="80" keywordseo="misra" source="Orion">Misra</keyword> 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. A solid gel electrolyte is used between the two FET electrodes to build a solid-state supercapacitor. The entire structure is built on a silicon dioxide/silicon base. Misra says, "The design is the critical part, because you are integrating two systems." The two systems are the two FET electrodes and the gel electrolyte, an ionic medium, which have different charge capacities, she added. Vinod Panwar, PhD student at IAP and one of the lead authors, adds that it was challenging to fabricate the device to get all the ideal characteristics of the transistor right. Since these supercapacitors are very small, they cannot be seen without a microscope, and the fabrication process requires high precision and hand-eye coordination. Once the supercapacitor was fabricated, the researchers measured the electrochemical capacitance or charge-holding capacity of the device by applying various voltages. They found that under certain conditions, the capacitance increased by 3,000 per cent. By contrast, a capacitor containing just MoS2 without graphene showed only an 18 per cent enhancement in capacitance under the same conditions. 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. They are also planning to apply for a patent on the supercapacitor. SEE ALSO: <a href="https://www.businessinsider.in/business/auto/news/no-festive-cheer-for-auto-cos-in-march-pv-sales-flattish-2ws-to-see-a-slight-uptick/articleshow/99145011.cms">No festive cheer for auto cos in March: PV sales ‘flattish’, 2Ws to see a slight uptick</a> <a href="https://www.businessinsider.in/stock-market/news/the-alpha-creators-bank-and-it-stocks-outperform-nifty50-in-the-last-11-years/articleshow/99114789.cms">The Alpha Creators: Bank and IT stocks outperform Nifty50 in the last 11 years</a> <a href="https://www.businessinsider.in/finance/news/npci-introduces-interchange-fees-on-upi-transactions-done-via-prepaid-payment-instruments/articleshow/99080455.cms">Will UPI payments now attract charges? Decoding NPCI’s interchange fee on UPI transactions via prepaid payment instruments</a>

IISc researchers design tiny supercapacitor capable of storing large amount of electric charge

Researchers at the Department of Instrumentation and Applied Physics (IAP), Indian Institute of Science (<keyword id="19910180" type="General" weightage="20" keywordseo="IISc" source="keywords" meta.keywordsubtype="org" meta.entityname="IISc" meta.hostid="83" meta.entityid="IISc">IISc</keyword>), and collaborators have designed a new <keyword id="23052480" type="General" weightage="20" keywordseo="supercapacitor" source="keywords">supercapacitor</keyword> that can be charged by shining <keyword id="19982220" type="General" weightage="20" keywordseo="light" source="keywords">light</keyword> on it. The supercapacitors can be used in various devices, including streetlights and self-powered electronic devices such as sensors, Bengaluru-based IISc said in a press release. "Capacitors are electrostatic devices that store energy as charges on two metal plates called <keyword id="20675368" type="General" weightage="20" keywordseo="electrodes" source="keywords">electrodes</keyword>. Supercapacitors are upgraded versions of capacitors - they exploit electrochemical phenomena to store more energy," Abha Misra, Professor at IAP and corresponding author of the study published in the 'Journal of Materials Chemistry A", was quoted as saying in the release. The electrodes of the new supercapacitor were made of Zinc Oxide (ZnO) nanorods grown directly on Fluorine-doped Tin Oxide (FTO), which is transparent. It was synthesised by Pankaj Singh Chauhan, first author and CV Raman postdoctoral fellow in Misra's group at IISc. Both ZnO and FTO are semiconductors with appropriately aligned energy levels, enabling superior performance of the photo-rechargeable supercapacitor, the release said. FTO, being transparent, allows light to fall on the optically active ZnO nanorods, which charges the supercapacitor. Chauhan explained that two electrolytes -- a liquid and a semi-solid gel -- were used as the conducting medium between the electrodes. The capacity for storing charges (<keyword id="23053496" type="General" weightage="20" keywordseo="capacitance" source="keywords">capacitance</keyword>) is inversely proportional to the distance between the electrodes, it said. "As the distance becomes very small, the capacitance shoots up," Misra stated. "In electrostatic capacitors, maintaining a small distance between electrodes is difficult. However, in a supercapacitor, the electrodes' charges attract the electrolyte's oppositely charged ions, resulting in the formation of a charge layer just atoms away from each other - called an electric double layer or EDL. This results in the high capacitance of supercapacitors," the release stated. 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, while capacitance generally decreases as the voltage increases, they found the reverse - their supercapacitor's capacitance under light illumination actually increased with increasing voltage. "We call it necking behaviour," said A M Rao, Professor at Clemson University, the USA, and co-author. He explained that this may be due to the high porosity of the electrodes. Second, the energy stored within the supercapacitor typically decreases when it is charged faster, because the ions in the electrolyte do not move fast enough to respond to the increased charging rate, the release said. However, with the liquid electrolyte, the team found that the energy stored in the supercapacitor surprisingly increased upon fast charging under UV light, it was noted. Mihir Parekh, a postdoctoral researcher in Rao's group, developed theoretical models to explain these novel observations. The findings open the doors to developing simultaneously fast-charging and energy-dense supercapacitors, according to him. 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 EDL. Together, these resulted in superior performance. "The ideas were simple - but when combined together, they worked very well," Misra explained. She added that tweaking the design of the supercapacitor can enable its charging with visible and infrared light as well. The IISc-Clemson team aims to further explore and better understand the novel phenomena observed to design better supercapacitors. "Supercapacitors have lots of applications," Misra explains. For example, they can potentially replace solar cells used in streetlights. They have a high power density, so they can release charge more quickly than batteries. They can also be used to power chips in electronic devices like cell phones. "We have miniaturised supercapacitors to the micron scale so that they can be integrated along with these microelectronic chips," Misra added.

IISc researchers, collaborators design supercapacitor that can be charged by shining light on it

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IISc researchers design tiny supercapacitor capable of storing large amount of electric charge

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IISc researchers, collaborators design supercapacitor that can be charged by shining light on it

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