Scientists at the Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru, an autonomous institute under the Department of Science and Technology (DST), have developed an innovative sunlight-powered supercapacitor capable of both capturing and storing solar energy in a single device. The breakthrough photo‑capacitor is being hailed as a major step toward clean, self-sustaining power systems that could benefit portable electronics, wearable devices and off-grid technologies.
Conventional solar energy setups rely on two separate components—solar panels for energy generation and batteries or supercapacitors for storage—along with additional electronics to regulate mismatched voltage and current levels. This increases the system’s cost, complexity and energy loss, posing limitations for compact or autonomous devices. The new photo-rechargeable supercapacitor eliminates these challenges by seamlessly integrating energy harvesting and storage within the same architecture, significantly reducing conversion losses.
Developed under the guidance of Dr. Kavita Pandey, the device uses binder‑free nickel‑cobalt oxide (NiCo₂O₄) nanowires uniformly grown on nickel foam through an in situ hydrothermal process. These nanowires, only a few nanometres thick and several micrometres long, form a porous and highly conductive 3D network that can efficiently absorb sunlight and store electrical charge simultaneously. This unique structure allows the nanowire electrode to function both as a solar energy harvester and as a supercapacitor electrode.
During performance tests, the NiCo₂O₄ electrode displayed a 54% increase in capacitance when exposed to light—rising from 570 to 880 mF cm⁻² at a current density of 15 mA cm⁻²—due to efficient generation and movement of light‑induced charge carriers. The electrode also showed long-term durability, retaining 85% of its initial capacity even after 10,000 charge-discharge cycles, a key requirement for practical applications.
To assess real‑world potential, the researchers fabricated an asymmetric photo‑supercapacitor using activated carbon as the negative electrode and NiCo₂O₄ nanowires as the positive electrode. The device delivered a stable output of 1.2 volts and maintained 88% capacitance retention after 1,000 photo‑charging cycles. It also operated reliably under a wide range of light conditions—from low indoor lighting to intense outdoor illumination—indicating its suitability for varied environments. The robust nanowire structure helped the device withstand both mechanical and electrochemical stress.
By combining energy generation and storage in a single platform, the new system demonstrates strong potential for deployment in remote or rural regions lacking electricity access, offering a self-sustaining, grid‑free power solution. The technology could also reduce dependence on conventional batteries and fossil fuels, contributing to India’s clean energy goals.
Complementing the experimental findings, researchers conducted theoretical simulations to understand the material’s exceptional efficiency. The study revealed that substituting nickel into the cobalt oxide lattice narrows the band gap to around 1.67 eV and induces half‑metallic behaviour—where the material behaves like a semiconductor for one electron spin and a metal for the other. This rare dual property boosts charge transport and electrical conductivity, making the nanowire system particularly effective for light-assisted energy storage.
The research highlights the synergy between experimental advances and theoretical modelling, offering insights into how nanostructured materials can be optimised for next‑generation renewable energy applications. Published in Sustainable Energy & Fuels, a journal of the Royal Society of Chemistry, the study introduces a promising class of smart, photo-rechargeable energy storage devices that could accelerate progress in sustainable energy technologies.
With further development, such integrated sunlight‑powered systems could play a transformative role in India’s renewable energy landscape and inspire innovations globally.
