ACAP Sydney University Node Lead Professor Anita Ho Baillie and her team are making important progress towards commercial viability of their perovskite-silicon tandem solar cell.
ACAP's verified 30% efficient perovskite-silicon tandem solar cell
Ho Baillie and her team have joined an elite global club of only 8 solar PV research groups in the world to demonstrate an independently certified 30% efficient monolithic perovskite-silicon tandem solar cell and, Ho Baillie says, they’re the first Australian group to achieve this certification.
They’ve also made significant gains improving the durability of their perovskite silicon tandem cells.
The work has been supported by ARENA and the Australian Centre for Advanced Photovoltaics, both of which are targeting 30% solar cell efficiency, at 30c per watt installed in the field, by 2030.
Silicon is the semiconductor material used in current solar technology, but it has a theoretical limit of around 30% energy conversion efficiency. Currently, the highest efficiency for a silicon cell is 27% produced in the laboratory.
To bring the cost of energy down further, ACAP researchers are studying different types of compound semiconductor materials for solar cells with high energy conversion efficiencies, that can also partner with silicon forming multijunction cells, and that will perform reliably in the field for many decades.
Metal halide perovskites are promising as they are cheap to produce because they can be printed or sprayed on very thinly and are suitable for light and flexible applications. They also don’t require the high temperatures during production that silicon cells.
Because perovskite cells convert short wavelengths of sunlight to electrical energy efficiently while silicon cells are better at converting long wavelengths of light, perovskite-silicon tandem cells have a higher theoretical energy conversion limit of around 45%.
“There are thousands of groups working towards this, but only 8 groups in the world can make 30% monolithic perovskite silicon tandem cells. We are in an elite group,” says Ho Baillie. “Our ultimate aim, though, is to achieve the 40% efficient cell.”
To realise double junction (tandem) cells, Ho Baillie and her team coated a semi-transparent perovskite layer onto a silicon cell to create a combined (monolithic) cell.
“Monolithic double junction solar cells have less wiring (fewer electrical leads) than mechanically stacked ones,” she explains.
Solving perovskite’s durability problem
For solar cells to become commercially viable, they need to be operating efficiently in the field for 25 years. But unlike silicon, perovskites are notoriously unstable. They are reactive to oxygen and moisture, temperature and light, all of which can cause degradation.
In 2020, Ho Ballie and her team attracted global attention for drastically improving the thermal stability of perovskite cells by stabilising them with a low-cost polymer-glass blanket with a pressure tight seal.
“We’ve managed to get the single junction perovskite cell to pass three of a suite of industry standard tests. It was a big deal when we published this!” says Ho Baillie.
Fast forward to year 2024, their tandem cells now are stable after 400 thermal cycles, twice the number set by the International Electrotechnical (IEC) standard. The work is published in Advanced Energy Materials.
The team are currently looking at the effect of combining light and heat stresses, and will publish a paper on this shortly. They also need to develop cost-effective, industry-relevant manufacturing processes.
From research to commercial scale
With efficiencies over 30% and work in progress on improving durability, the next step for tandem technologies is to scale from the 1cm2 research cells reported here, to commercial scales of 300 - 400 cm2 that are needed to be compatible with silicon wafer based processes, and to continue to drive costs down with economies of scale and a focus on sustainable manufacutring.
They’ve partnered with Australian solar technology company SunDrive which has developed low-cost metallisation technology for solar cells, replacing the use of silver with cheaper more abundant copper. SunDrive is collaborating with AGL in a bid to start up solar panel manufacturing in the Hunter Valley.
With the ongoing support of ACAP and ARENA, and SunDrive, Ho Baillie’s team can continue their work increasing the commercialisation prospects of perovskites and their Australian perovskite-silicon tandem cell.
Professor Ho-Baillie leads the University of Sydney’s node of the Australian Centre for Advanced Photovoltaics (ACAP). She is the John Hooke Chair of Nanoscience at Sydney University.
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