Dreams of powering entire buildings with solar power could be closer than ever, thanks to a thin, cheap and non-toxic solar cell produced by a team from UNSW.
CZTS cells are made from copper, zinc, tin and sulphur – cheap, abundant, and non-toxic materials. Similar thin-film solar cells have been held back by cost and toxicity problems. CdTe cells (made from cadmium and telluride) are used in large solar power farms, but cadmium is highly toxic and can’t be used to power homes.
Meanwhile CIGS cells (from copper, indium, gallium and selenium) are becoming increasingly expensive as the price of indium rises due to its use in modern tech, such as your smart phone.
“Indium is in large demand in LED and LCD technology, and we believe that market will keep increasing, so the price of indium will keep increasing,” says Hao. “We need to find some solution to replace those two [types of cells].”
World's most efficient
The team has been working for about three years to increase the size and efficiency of their CZTS cell. This month the National Renewable Energy Laboratory in the US confirmed these are the most efficient full-sized thin-film cells in the world - at 7.6% per square centimetre.
“This is a big jump, and a big step for us. There is still a lot of work needed to catch up with CdTe and CIGS, in both efficiency and cell size, but we are well on the way,” says Hao.
The next step is to work towards 20% efficiency, allowing the cells to be used commercially, and integrated into tandem solar cells with silicon to boost efficiency.
The technology could be especially useful in countries with large buildings.
“In Australia, everyone can have a solar panel on the roof; in Asian countries, there are a lot of buildings. You could put a panel on the roof, but I don’t think it’s going to be enough for all the people in the same building.”
According to Hao, being able to use flexible solar panels on the side of the building would make a big difference.
To get these new cells to a commercial stage there are still challenges to overcome, but Hao is hopeful.
“There are a lot of things we need, almost like a magic trick. But I think with more magic solutions to overcome the obstacles for this technology, we will make it.”
Babies hone time management
Finding magical solutions is what drove Hao, named one of UNSW’s 20 Rising Stars in 2015, to study and work in engineering.
“I like engineering, I like to make something, to make it happen,” Hao says. “It’s like - there’s a problem, and there’s a solution. I like that feeling of achievement, by solving problems.”
Hao notes there weren’t many other women undertaking her degree, which could be challenging – but she finds the work rewarding and the outcomes satisfying.
She also added that her time management skills were actually sharpened by having two children and taking maternity leave during her research.
“I know that babies might sleep for one hour, so I know that in that hour I can work on something, and I know I need to finish in that one hour. So I’ll be trying to focus on that and finish it,” she says. “So then, one hour, the baby wakes up, okay – I go back to the baby, and then I work around it. It makes you work more efficiently,” she adds.
“So I never feel like working and having babies is a burden, I feel like it’s my life. I’m happy and I enjoy the time with my kids, and I enjoy the time with my work.”