Indian scientists have developed an innovative sunlight-powered supercapacitor, known as a photo-capacitor, that can capture and store solar energy in a single integrated device. The breakthrough marks a significant step towards clean, self-sustaining, and low-cost energy storage systems, with promising applications in portable electronics, wearables, and off-grid technologies.
The research was carried out by scientists at Centre for Nano and Soft Matter Sciences (CeNS), an autonomous institute under the Department of Science and Technology (DST), Government of India.
Overcoming Limitations of Conventional Solar Systems
Traditional solar energy systems rely on two separate units—solar panels for energy harvesting and batteries or supercapacitors for storage. Such hybrid systems require additional power management electronics to regulate voltage and current mismatches, increasing:
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System complexity
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Energy losses
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Cost and device footprint
These drawbacks are particularly challenging for miniaturised and autonomous devices. The newly developed photo-rechargeable supercapacitor addresses these issues by seamlessly integrating energy harvesting and storage into a single architecture.
Innovative Nanowire-Based Design
Under the guidance of Dr. Kavita Pandey, the research team developed the device using binder-free nickel–cobalt oxide (NiCo₂O₄) nanowires, uniformly grown on nickel foam through a simple in-situ hydrothermal process.
The nanowires—only a few nanometres in diameter and several micrometres long—form a highly porous, conductive three-dimensional network. This unique structure enables the material to act simultaneously as:
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A solar energy harvester
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A supercapacitor electrode
This dual functionality significantly reduces energy loss during conversion and storage.
Exceptional Performance and Stability
Performance testing revealed remarkable results:
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Capacitance increased by 54% under illumination, rising from 570 to 880 mF cm⁻² at a current density of 15 mA cm⁻²
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After 10,000 charge–discharge cycles, the electrode retained 85% of its original capacity, indicating strong long-term stability
The enhanced performance is attributed to efficient generation and transfer of light-induced charge carriers within the nanowire network.
Real-World Applicability Through Asymmetric Device Design
To assess practical usability, researchers fabricated an asymmetric photo-supercapacitor, using activated carbon as the negative electrode and NiCo₂O₄ nanowires as the positive electrode.
Key outcomes included:
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Stable output voltage of 1.2 volts
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88% capacitance retention after 1,000 photo-charging cycles
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Reliable operation across varied lighting conditions—from low indoor light to intense two-sun illumination
These results demonstrate the device’s resilience to mechanical and electrochemical stress over prolonged use.
Theoretical Insights Behind High Efficiency
Alongside experiments, theoretical studies were conducted to understand the material’s exceptional performance. The analysis revealed that nickel substitution in the cobalt oxide framework:
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Narrows the band gap to approximately 1.67 eV
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Induces half-metallic behaviour, where the material acts as a semiconductor for one electron spin and metallic for the other
This rare property enables faster charge transport and higher electrical conductivity, making it especially suitable for photo-assisted energy storage.
A Step Towards Sustainable and Decentralised Energy
By integrating sunlight harvesting and charge storage in a single device, the research opens the door to self-charging power systems capable of functioning even in remote regions without grid access. Such systems could substantially reduce reliance on fossil fuels and conventional batteries, supporting India’s clean energy transition.
The findings, published in Sustainable Energy & Fuels, introduce a new class of smart, photo-rechargeable energy storage devices and demonstrate the powerful synergy between experimental and theoretical materials research.
Conclusion
This breakthrough represents a paradigm shift in renewable energy storage, showcasing how nanostructured materials can be optimised for light-responsive performance. With further development and scaling, such technologies could play a pivotal role in achieving India’s clean energy ambitions and inspire similar innovations worldwide.
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Source: PIB
