Researchers at the University of NSW have utilised the light-trapping effects of a simple prism to dramatically boost the efficiency of solar cells.

Martin Green and Mark Keevers said the device they have built has set a world record for sunlight-to-electricity efficiency using "unfocused light" – the sort of sun that hits our roofs.

The UNSW team said its mini-module converts 34.5 per cent of received solar energy into electricity. The result, confirmed by the US National Renewable Energy Laboratory, has eclipsed the 24 per cent efficiency achieved by an 800-square-centimetre commercial module made by Alta Devices in the US. The UNSW module is 28 square centimetres.

Typical efficiency for commercially available solar panels is 14 to 22 per cent.

Other solar cells have obtained higher efficiencies from unfocused sunlight, but these results were achieved before being placed into prototypes or modules that could be scaled up for commercial use.

"​The intention is for our device to be suitable for rooftop photovoltaics, but this is a longer-term proposition," said Dr Keevers, senior research fellow at UNSW. "What we've done is a very early-stage [expensive] prototype.

"Our next step is to see if we can use [the prism and] the associated spectrum-splitting to make cheaper modules that could go on the roof of your house," he said.

Professor Green, who is director of the Australian Centre for Advanced Photovoltaics, said any commercialisation is more than 10 years away.

Andrew Thomson at the Australian National University school of engineering, who is unconnected with the research, said UNSW's work was "pushing boundaries" and "leading the way for the rest of the industry".

The UNSW solar cell is designed to maximise energy squeezed out of light hitting the receiver. This is achieved using a triple-junction cell that can absorb energy in three discrete wavelength bands of light as it arrives from the sun.

A solar splitter filters out otherwise unused infrared light to a fourth junction, further increasing efficiency.

​Typical domestic silicon-wafer solar cells take energy from the sun in one hit and so convert a lower proportion of light to electricity.

"Our module uses the light-trapping effect of a simple prism to maximise the amount of sunlight available to the solar cell," Professor Green said.

"Unlike focused cells from mirror arrays, our module responds to light from any direction. This light then bounces around inside the prism."

The UNSW result was obtained by the same team that in 2014 set a conversion rate record of more than 40 per cent using mirrors to concentrate the light.

Dr Keevers said the aim was to lower the cost of solar energy to parity or under that of coal to allow a transition to an economy based on renewables.

"Photovoltaics have reached grid parity to compete with coal in some markets and times of day," he said.

John Lasich is the chief technology officer at RayGen, which is working with UNSW to achieve commercially viable solar energy. Dr Lasich said the UNSW result is "a demonstration of how efficient solar devices can be".

He said that while these prototypes are pretty expensive, they put UNSW at the vanguard of pushing the efficiency of solar panels higher. "Put into an array you could use them in high-value areas, such as satellites," he said.

RayGen is using technology similar to that developed by UNSW in 2014 that uses focused sunlight to produce energy. With partners in China, RayGen Research by Professor Green and Dr Keevers in 2014 broke records for a four-junction device using commercially available silicon panels, pushing sun-to-electricity efficiency above 40 per cent.

UNSW's research was supported by $1.4 million grant funding from the Australian Renewable Energy Agency and funds from UNSW with RayGen; Trina Solar; and the US National Renewable Energy Laboratory.

Solar-cell efficiency over time. Photo: US National Renewable Energy Lab