Sunlight-Powered Supercapacitor Stores Energy Directly, Indian Scientists Report

The newly developed photo-capacitor overcomes this limitation by performing both functions simultaneously.

Indian researchers have unveiled a breakthrough energy device that can both capture sunlight and store it instantly—eliminating the need for separate solar panels and batteries. The innovation, known as a photo-rechargeable supercapacitor or photo-capacitor, marks a major step toward compact, low-cost, and self-sustaining power systems for next-generation electronics.

Developed by scientists at the Centre for Nano and Soft Matter Sciences (CeNS), Bengaluru, an autonomous institute under the Department of Science and Technology (DST), Government of India, the device integrates solar energy harvesting and storage into a single architecture. This streamlined design drastically reduces system complexity, energy losses, and cost—key barriers in today’s renewable energy technologies.

One device, two functions

Conventional solar systems rely on separate components: photovoltaic cells to capture energy and batteries or supercapacitors to store it. These hybrid setups require additional power-management electronics to handle voltage and current mismatches, increasing size and inefficiency—especially problematic for miniaturised, wearable, and off-grid devices.

The newly developed photo-capacitor overcomes this limitation by performing both functions simultaneously.

Under the guidance of Dr Kavita Pandey, the research team engineered a binder-free electrode using nickel–cobalt oxide (NiCo₂O₄) nanowires grown directly on nickel foam through a simple in-situ hydrothermal process. The result is a highly porous, conductive three-dimensional network that efficiently absorbs sunlight while storing electrical charge.

Performance boosted by light

The nanowire electrode demonstrated a 54% increase in capacitance under illumination, rising from 570 to 880 mF cm⁻² at a current density of 15 mA cm⁻². Even after 10,000 charge–discharge cycles, it retained 85% of its capacity, highlighting its durability for real-world applications.

To test practical usability, the researchers assembled an asymmetric photo-supercapacitor using activated carbon as the negative electrode and NiCo₂O₄ nanowires as the positive electrode. The device delivered a stable 1.2-volt output, retained 88% capacitance after 1,000 photo-charging cycles, and functioned reliably across a wide range of lighting conditions—from indoor light to intense two-sun illumination.

Why it works so well

Alongside experiments, the team conducted theoretical simulations to uncover the material’s exceptional performance. The study revealed that nickel substitution narrows the band gap to about 1.67 eV and induces half-metallic behaviour—a rare property where the material behaves as a semiconductor for one electron spin and metallic for the other. This enables faster charge transport, higher conductivity, and enhanced photo-assisted energy storage.

A call to early adopters

By merging sunlight capture and storage in one compact unit, the photo-capacitor opens the door to self-charging power sources that can operate anywhere—even in remote regions without grid access. The technology holds strong promise for portable electronics, wearables, sensors, and off-grid energy systems, while reducing reliance on fossil fuels and conventional batteries.

Published in Sustainable Energy & Fuels (Royal Society of Chemistry), the study introduces a new class of smart, light-responsive energy storage devices. The researchers now invite industry partners, device manufacturers, and clean-energy innovators to explore early adoption and scale-up of this technology as part of India’s clean-energy transition.