Australian startup SunDrive has created a commercial-sized silicon solar cell with 25.54 per cent efficiency using copper instead of silver.
Led by co-founders Vince Allen, an engineer, and David Hu, Sundrive’s cell achieved an efficiency of 25.54 per cent — beating the old record of 25.26 per cent — in testing carried out by the Institute for Solar Energy Research in Germany.
“We’re only at the very early stages of where the industry can be, with only 3 per cent of the world’s electricity currently coming from solar,” Allen said in an announcement.
“If we want to get to 50, 60, 70 per cent and beyond, we’re going to need a lot more solar cells and that’s a massive challenge.”
The world record holder back in 2014, and a former colleague of Allen’s at the University of University of New South Wales (UNSW), Professor Martin Green told create that the breakthrough was exciting on a number of levels.
“It could be really important. The traditional way of extracting the current from the cell has been with silver, but last year, solar used 10 per cent of the world’s silver supply, and the industry is growing quickly,” he said.
Copper is about 100 times cheaper than silver, and it also requires lower processing temperatures, meaning less energy consumption to create cells.
“It’s not a material that you want to have your industry dependent on, because it’s used in jewellery and other commercial activities so that the price can become very volatile,” he said.
“Vince has found another way of applying these metal lines to silicon cells that uses copper, rather than silver.”
Ordinarily, silver is mixed into a paste and ‘screen printed’ onto a cell before being heated to about 750°C. The technology that SunDrive applied can’t stand high temperatures.
“That’s going to make it easier to get this other technology onto the market, because the cost of the silver is inhibiting,” he said.
Hurdles to get to market
“It’s not just the efficiencies SunDrive has been working on, but the durability issues that you need a new approach to satisfy,” Green said. “Vince Allen has been doing work in that area, but that’s not quite as exciting as the new efficiency record.”
Green believes that SunDrive’s copper breakthrough will certainly refocus attention on the metal in solar because of its obvious benefits.
“There are a lot of physical limits to efficiency, so 68 per cent is the limit for a solar cell. Presently, cells are made from silicon — the way you can get to these much higher efficiencies is by stacking cells made from different materials,” he said.
Green added that his researchers have made cells that are 50 per cent efficient, but only at converting red light.
“The ultimate way to approach that 68 per cent efficiency is by having cells specialised to convert each colour of the photons. But for a silicon cell, the efficiency limit is about 29 per cent — so SunDrive is getting quite close to that,” he said.
The global race continues
Green said that UNSW held the efficiency record for 30 years, but the proliferation of solar companies means that universities are finding it hard to compete due to scale.
“The industry is using the PERC cell that was developed at UNSW, so over 90 per cent of the cells made globally are using Australian invented and developed technology,” he said.
“We have a good reputation, so that makes it easy for people like Vince Allen to get attention when they come up with something like this, because Australia has such a reputation for being pioneers with technology.”
Universities and firms in Europe, Asia, the United States and Australia are all continuing to compete for efficiency gains.
In 2016, German think tank Agora Energiewende set an aggressive target of 35 per cent efficiency by 2050 for a module that uses unconcentrated sunlight, such as the standard solar cells used on family homes.
Last year, British researchers Oxford PV claimed that the next-generation of solar panels would be able to generate almost a third more electricity than traditional silicon-based solar panels by coating the panels with a thin layer of a crystal material called perovskite.
Green said that commercialisation of such breakthroughs can happen quickly, but manufacturers need to ensure efficiency doesn’t come at the cost of durability.
“You’ve got to make sure that you’re not jeopardising the extreme reliability by making a change,” he said.
“That’s the big hurdle. A company would have to do extensive testing under certain conditions to make sure they were satisfied that switching to a new technology like this wouldn’t prejudice the durability of the product that they’re offering their customers.”
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