This summary is drawn from a presentation delivered by ACAP Program Lead Professor Dan Macdonald (ANU) at the ACAP 2024 Conference where he outlined the current status, challenges, opportunities and some highlights.
Alternatively, scroll to the bottom to watch a video of Dan's presentation.
Substantial breakthroughs in silicon solar cell development are possible in the next five years with accelerated R&D.
ANU collaborates with UNSW and Melbourne University teams in the silicon solar cell development program.
Status of silicon solar cell technology development
Modules: Silicon solar modules with efficiencies above 25% are coming onto the market.
Full size HJT cells: This year has seen a number or record efficiencies for full size cells. Longi achieved a 27.4% silicon heterojunction (HJT) cell this year and Professor Macdonald predicts these records will be broken in the next 6 months.
TOPCon cells: Chinese manufacturers Jinko, Trina and others are very close to full size 26% certified efficiency with standard TOPCon architecture cells.
TOPCon technologies are currently surpassing HJT coming onto the market and, according to Professor Macdonald, most of the new factory lines being built in industry are TOPCon lines.
Bifacial modules: These offer an important 10-15% energy gain and are the dominant technology in utility-scale PV applications.
Back contact cells: Back contact architecture is likely to be the next iteration in silicon cell technology. They have potential to get to 28% efficiency but they’re still in development.
Silicon bottom cells for tandem cells: These are evolving rapidly, with a lot of promise coming in the form of lower cost polysilicon contacts which are just as efficient as heterojunction cells.
Current challenges with silicon solar cells
Advancements need to be achieved in surface passivation, wafer quality, thinner cells, light trapping, reducing reflection from the front surface, and minimising parasitic absorption.
Critically, we need to remove reliance on silver as much as possible, and transition to alternative contact materials such as copper. We need to develop new ways of patterning these contacts with fine line resolution and high conductivity.
Professor Dan Macdonald reports that they are seeing almost defect-free silicon wafers being produced by industry partner Longi.
Opportunities for ACAP and industry
ACAP has world-leading expertise and capabilities in Si cells at ANU, UNSW and Melbourne University, as well as excellent links to industry. Professor Macdonald predicts that, with accelerated R&D effort and cross disciplinary collaborations in new materials and cell designs and processes, we can reach 28% efficiencies at the research scale in large size silicon single junction cells (and 26% for modules) in the next 2-5 years.
Achieving 30% effective efficiency, including bifacial gains, by 2030 is realistic without significantly increasing manufacturing costs.
Silicon solar cells are an ideal platform for tandem devices, approaching 40% efficiency in 5-15 years. Cross-disciplinary collaborations will play a vital role in integrating emerging materials and processes.
Macdonald identified transparent passivating contacts as a major area of research offering potential efficiency improvements.
Highlights for ACAP’s Si research
Major advances have been made in wafer quality by partner Longi in China. Reduced oxygen content in the wafers minimises defects, allowing for better performance. Wafers are now close to the theoretical efficiency ceiling for silicon solar cells.
ACAP’s combined activity between ANU, UNSW and Melbourne University has seen rapid improvements in transparent metal oxide contacts and transparent contacts in general.
We have made good progress on chlorine doped passivating contacts which improves UV stability and provides outstanding passivation, as well as giving good contact, and with potential for efficiency above 25% with a transparent contacting layer.
We’ve developed printed P+ doped poly-Si contacts for low cost rear contact cells.
Watch the video
Readers can find the full details on progress and activities in each program in Chapter 5 of ACAP’s Annual Report. The 2024 Annual Report will be published in May 2025.
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