An update on the current status, challenges, opportunities and highlights in ACAP's emerging PV materials program. This is a summary of the presentation delivered by ACAP Program Lead Dr Anthony Chesman at the ACAP 2024 Conference. You can view the video of his presention below.
All ACAP nodes are involved in research on emerging materials, covering all material types (perovskites, kesterite and organic PV). ANU and UNSW are achieving internationally competitive efficiencies for tandem structures.
Status of emerging PV materials research
Research has been dominated by perovskite solar cells but advances in organic and kesterite solar cells continue. It’s clear now that the materials can deliver the performance we need in terms of cell efficiency, but the challenge now is to find a material that is also stable and easy to fabricate.
Some of the emerging materials are now being translated to tandem solar cells.
Perovskite solar cells: Perovskites dominate current research due to ease of fabrication and high efficiencies over 26%, but they currently lack the stability required to incorporate into tandems. Improvements must be made before they are market-ready and ACAP nodes are focused on this.
Some manufacturers are making progress with pilot scale lines for perovskite solar cell manufacturing, but they face the same challenges with material stability.
Kesterite: Kesterites, which include copper-zinc-tin-sulfide cells (CZTS), have lower efficiencies but are more stable. Kesterite solar cells are attractive because they can be made from nontoxic and earth-abundant elements. UNSW has delivered a world-leading 13.2% efficiency for CZTS solar cells.
Organic Photovoltaics (OPV): These have been in labs for around for 20 years but are gaining renewed attention with efficiencies now surpassing 20%, aided by advancements in small molecule acceptors. Organic PV offer a mix of stability and efficiency, and are easy to fabricate.
They are also being introduced into tandem solar cells.
Multiple Exciton Generation: MEG materials offer routes to higher efficiencies.
Groups are looking beyond Si perovksite tandems towards new tandem architectures such as perovskite-perovskite or OPV-perovskite or triple junction tandem devices.
Efficiencies: ACAP Nodes have demonstrated world leading efficiencies across a number of device architectures and material classes:
· ANU achieved a 26.7% n-i-p single junction perovskite solar cell.
· UNSW achieved a 13.2% CZTS solar cell
· UNSW achieved a 10.7% antimony chalcogenide
ACAP’s high-throughput production systems allow for rapid fabrication and optimisation of solar cells.
At CSIRO, we’ve commenced scaled demonstration of thin-film solar cell production, using equipment co-funded by ARENA in the ACAP infrastructure round.
Challenges with emerging PV materails
Material stability: While high efficiencies are achievable, the stability of emerging materials, especially perovskites, remains insufficient for commercial adoption.
Bandgap optimisation: The need to modify material properties, such as band gap, for compatibility in tandem devices adds complexity. Most previous work was on optimising materials for single junction solar cells.
Competition and breadth of materials: The solar research field is highly competitive with rapid publication rates. There are also many options to explore and it’s challenging for ACAP to build critical mass in new material types while maintaining leads in existing areas. We need to keep an eye on emerging areas to stay competitive.
Benchmarking stability for commercialisation: Historically there has been a focus on efficiency as the marker of progress, motivated by publication opportunities, but this overlooks stability and durability. There are calls for a universal stability-focussed figure of merit and testing regimes to shift priorities towards commercialisation.
Complex device architecture: The many integrated layers in tandem devices must be finely tuned and they increase fabrication complexity.
Opportunities with emerging materials
Despite the highly competitive environment, ACAP does have key advantages thanks to strategic investment in tools and facilities across the nodes.
Advanced tools, like high throughput fabrication and screening equipment,, accelerate the development process and reduce material waste.
Automation and machine learning are rapidly changing the nature of research in the field and are key to staying competitive. With AI and machine learning we can increase the throughput of production and use our researchers more effectively.
Examples include the high throughput production facility at Monash and CSIRO’s Microfactory equipment, which can produce 14,000 unique solar cells in a day. We can take the results of these systems and use them to program machine learning algorithms to predict optimised deposition parameters and compositions for even higher efficiency devices.
We have also demonstrated pilot scale thin film solar cell production domestically, underlining Australia’s capability in solar manufacturing.
We are yet to fully explore computational modelling of new compositions to predict the properties before we’ve synthesised the materials. This will allow us to deduce whether they will provide efficiencies that are feasible or even worth fabricating.
Some highlights from the ACAP Nodes
ACAP’s University of Sydney team is one of only six groups to report 20% 1cm2 perovskite-organic PV tandem.
ACAP collaboration with Monash and Oxford University on advanced passivation processing has delivered a relatively stable perovskite solar cell with an efficiency over 26%.
ACAP’s University of Queensland team produced high-efficiency blade-coated perovskite solar cells with fluorinated additives.
Monash has developed a scalable microstamping approach for perovskite materials, with applications in semi-transparent building integrated PV.
CSIRO reported the highest efficiency for a fully printed perovskite module.
Readers can find the full details on progress and activities in each program in Chapter 5 of ACAP’s Annual Report 2024 which will be published in May 2025.
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