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A Buddhist Approach to Solar Cell Design

The shape of a centuries-old Buddhist singing bowl has inspired Dr Niraj Lal of The Australian National University to rethink the design of solar cells to maximise their efficiency.

Normally used in meditation, music and relaxation, Buddhist singing bowls make a continuous harmonic ringing sound when the rim of the metal bowl is vibrated with a wooden or other utensil.

During his PhD at the University of Cambridge, Niraj found that small nano-sized versions of Buddhist singing bowls resonate with light in the same way as they do with sound. He has now applied this shape to solar cells to increase their ability to capture more light and convert it into electricity.

“Current standard solar panels lose a large amount of light energy as it hits the surface, making the panels’ generation of electricity inefficient,” Niraj says. “But if the cells are singing bowl-shaped, then the light bounces around inside the cell for longer.”

During his PhD, Niraj discovered that his “nanobowls” manipulated light by creating a “plasmonic” resonance that quadrupled the laboratory solar cell’s efficiency compared with a flat solar cell.

Niraj is now applying his discovery to tandem solar cells: a technology that has previously been limited to aerospace applications.

In research published in the November issue of IEEE Journal of Photonics, Niraj and his colleagues have shown that by layering two different types of solar panels on top of each other in tandem, flat rooftop solar panels can achieve 30% efficiency. Currently, laboratory silicon solar panels convert only 25% of light into electricity while commercial varieties convert closer to 20%.

The tandem cell design absorbs sunlight more effectively. Each cell is made from a different material that can absorb a different wavelength of light.

“To a silicon solar cell, a rainbow just looks like a big bit of red in the sky. They don’t ‘see’ the blue, green or UV light – they convert all light to electricity as if it was red,” Niraj says. “But when we put a second cell on top that ‘sees’ the blue part of light but allows the red to pass through to the ‘red-seeing’ cell below, we can reach a combined efficiency of more than 30%.”

Niraj and a team at The Australian National University are now looking to super-charge the tandem cell design by applying the Buddhist singing bowl shape to further increase efficiency. “If we can make a solar cell that ‘sees’ more colours and keeps the right light in the right layers, then we could increase efficiency even further,” Niraj says.