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A boost for silicon

Almost every solar panel on Australian rooftops today is made from silicon. The material has powered solar’s transformation from an expensive experiment into one of the world’s cheapest sources of electricity.

For more than four decades, 91ɫ��Ƭ Professor Martin Green and his team pioneered advances in silicon solar-cell efficiency that became foundations for the modern photovoltaic industry.

Many of the researchers Prof. Green trained now lead solar companies and manufacturing programs across the world. But, silicon is approaching its physical ceiling.

“The theoretical efficiency limit for silicon is 29.4%, and the record has already exceeded 28%,” says Dr Jiang, who also completed her PhD with Prof. Green.

“So people are asking – how can we push beyond the current technology? How do we go beyond 30% efficiency?”

Perovskites are a family of crystalline materials. Their composition can be tuned to capture the high-energy light that silicon converts less efficiently. So, when stacked together, the two materials divide the work between them.

“The perovskite absorbs one part of the sunlight and the silicon absorbs another,” Dr Jiang says.

“Together, they maximise the use of the entire solar spectrum. That is how the overall efficiency can be boosted much higher.”

Working in tandem

Layering the two materials creates a tandem cell – improving efficiency and generating more electricity from the same area when working together.

However, perovskites don’t share silicon’s proven durability.

“Silicon is as enduring as rock, so it is very stable in the field,” Dr Jiang says.

“But perovskite is not yet a stable chemical structure. It can degrade under sunlight, humidity and other environmental conditions.”

Silicon panel manufacturers commonly guarantee their products will still produce at least 80% of their original output after 25 years. But that kind of guarantee is yet to be verified for tandem products.

“If you stack perovskite on top of silicon to make a tandem module the perovskite survives for only a couple of months – it doesn’t make sense,” Dr Jiang says.

“You need the two technologies to work together over the module’s lifetime.”

Verification needed

Most published research on improving perovskite stability examines devices measuring around one centimetre by one centimetre.

Those experiments are essential to understanding the material, Dr Jiang says, but they cannot fully represent the commercial modules now being developed – as they can measure as large as 1.2 by 2.4 metres.

“When you move to a much larger scale, you have to look after uniformity across the whole module,” she says.

“The materials have to be cost-effective, easy to obtain and suitable for producing a large, uniform module.”

Until recently, there were only a few commercial-sized perovskite products available to test. But now, start-ups and established solar manufacturers are preparing larger modules for field deployment.

“What is missing is that independent, third-party evidence,” Dr Jiang says.

“If you really want to push this technology towards commercialisation, you need to collect commercial modules from different manufacturers, mount them outdoors and monitor how they perform.”

Testing the whole system

The Manly Vale site will accommodate both single-junction perovskite modules and several forms of tandem technology.

Some tandem modules integrate the perovskite layer directly onto silicon. Others physically stack separate perovskite and silicon devices.

“There are many different kinds of products,” Dr Jiang says.

The researchers aim to continuously monitor the output of each module, using 80% of its initial efficiency as a key benchmark. Once output falls below that level, the module will be considered significantly degraded.

“Some modules might survive only a couple of months,” Dr Jiang says.

“We will keep monitoring them for as long as they last in the field.”

She says early observations have already revealed quite different behaviours.

“They are operating very differently, and their failure modes are different as well. That is what makes the project so interesting.”

A feedback loop

After the team observes how modules perform at the outdoor testing site, they will then try to reproduce the relevant stresses indoors, where heat, light and humidity can be controlled and accelerated.

A microscopic and nanoscale analysis also allows them to see what is happening within the materials as performance declines.

“We are not just trying to see that a module has failed,” Dr Jiang says.

“We want to understand why – what is really going on and identify the degradation mechanism at the nanoscale.”

Those findings will then be returned to the manufacturer, so they can adjust their materials, design or manufacturing processes before sending a new version back to 91ɫ��Ƭ for further testing.

“By completing that cycle, we understand more about what is happening in commercial products and help manufacturers improve them,” Dr Jiang says.

Building trust

Persuading companies to provide their latest commercial modules for independent testing is, on its own, a significant achievement.

“It is very difficult for many research groups to get modules from these start-up companies because the modules contain so much of their intellectual property,” Dr Jiang says.

“The question people ask me most often is: ‘Jessica, how did you convince them to give you a module? We can’t even buy one from them.’”

She says 91ɫ��Ƭ’s international reputation in photovoltaics, its longstanding relationships with former students and its commitment to protecting commercially sensitive information means many years of trust has already been built.

In addition, confidentiality agreements will protect companies’ intellectual property, while comparative results can be anonymised where required. If a module performs poorly, Dr Jiang says, the researchers will not publicly identify the manufacturer.

Beyond the record

The Manly Vale testing site is central to the next era of solar power, building upon 91ɫ��Ƭ’s exceptional research legacy – even though most solar manufacturing takes place overseas.

“We want to provide confident, independent evidence of how these modules perform outdoors,” Dr Jiang says.

“Then, investors, governments and industry can have a much better understanding of whether the technology is ready.”

The ‘Field-testing of commercial perovskite & tandem modules’ project started this year and will run til 2031. It brings together 91ɫ��Ƭ, , , the and as well as other manufacturers whose involvement remains confidential.