Australian engineers have set a new world record for sunlight-to-electricity conversion.

A new solar cell configuration developed at the University of New South Wales has pushed sunlight-to-electricity conversion efficiency to 34.5 per cent.

It is a new official world record for unfocused sunlight, and brings scientists closer to the theoretical limits for the device.

The record was set by Dr Mark Keevers and Professor Martin Green at the UNSW’s Australian Centre for Advanced Photovoltaics, using a 28-cm2 four-junction mini-module to extract the maximum energy from sunlight.

The new result, confirmed by the US National Renewable Energy Laboratory, is almost 44 per cent better than the previous record. It was set when US firm Alta Devices reached 24 per cent efficiency, but over a larger surface area of 800-cm2.

“This encouraging result shows that there are still advances to come in photovoltaics research to make solar cells even more efficient,” said Keevers.

“Extracting more energy from every beam of sunlight is critical to reducing the cost of electricity generated by solar cells as it lowers the investment needed, and delivering payback faster.”

The result was obtained by the same UNSW team that set a world record in 2014 for an electricity conversion rate of over 40% by using mirrors to concentrate light – a technique known as CPV (concentrator photovoltaics).

The new result was achieved using normal sunlight with no concentrators.

“What’s remarkable is that this level of efficiency had not been expected for many years,” Mr Green said.

“A recent study by Germany’s Agora Energiewende think tank set an aggressive target of 35 per cent efficiency by 2050 for a module that uses unconcentrated sunlight, such as the standard ones on family homes.

“So things are moving faster in solar cell efficiency than many experts expected, and that’s good news for solar energy.

“But we must maintain the pace of photovoltaic research in Australia to ensure that we not only build on such tremendous results, but continue to bring benefits back to Australia.”

Australia’s research in photovoltaics has already generated flow-on benefits of more than $8 billion to the country, Green said.

Gains in efficiency alone are forecast to save $750 million in domestic electricity generation in the next decade.

The record-setting UNSW mini-module combines a silicon cell on one face of a glass prism, with a triple-junction solar cell on the other.

The triple-junction cell targets discrete bands of the incoming sunlight, using a combination of three layers: indium-gallium-phosphide; indium-gallium-arsenide; and germanium.

As sunlight passes through each layer, energy is extracted by each junction at its most efficient wavelength, while the unused part of the light passes through to the next layer, and so on.

Some of the infrared band of incoming sunlight, unused by the triple-junction cell, is filtered out and bounced onto the silicon cell, thereby extracting just about all of the energy from each beam of sunlight hitting the mini-module.

The 34.5 per cent result with the 28 cm2 mini-module is already a world record, but scaling it up to a larger 800-cm2 – thereby leaping beyond Alta Devices’ 24 per cent – is well within reach.

“There’ll be some marginal loss from interconnection in the scale-up, but we are so far ahead that it’s entirely feasible,” Keevers said.

The theoretical limit for such a four-junction device is thought to be 53 per cent, which puts the UNSW result two-thirds of the way there.

Multi-junction solar cells of this type may not appear on rooftops of homes and offices anytime soon, as they require more effort to manufacture and cost more than standard crystalline silicon cells with a single junction.

However, the UNSW team is working on new techniques to reduce the manufacturing complexity, and create cheaper multi-junction cells.

The spectrum-splitting approach is also perfect for solar towers, which use mirrors to concentrate sunlight before converting it into electricity.

The research is supported by the Australian Renewable Energy Agency (ARENA).

ARENA CEO Ivor Frischknecht said the achievement demonstrated the importance of supporting early stage renewable energy technologies.

“Australia already punches above its weight in solar R&D and is recognised as a world leader in solar innovation,” Frischknecht said.

“These early stage foundations are increasingly making it possible for Australia to return solar dividends here at home and in export markets – and there’s no reason to believe the same results can’t be achieved with this record-breaking technology.”