Mapping the path to commercially scalable tandem solar cells
By Alison Potter
Can the new silicon solar technology currently dominating global manufacturing also provide the foundation for the next generation of high-efficiency solar cells?
That is one of the key questions addressed by a new and very practical collaborative review in Joule, by ACAP-supported researchers from ANU, the University of Melbourne and UNSW, and global solar manufacturer Jinko Solar.
The question is timely. Conventional silicon solar cells are approaching their practical efficiency limit, with champion cells now crossing 28% efficiency and approaching a practical limit of around 29.4%. Further substantial gains are therefore expected to come from tandem solar cells, which combine two light-absorbing materials to capture more of the sun’s energy.
Shifting the focus from efficiency to commercial potential
With industry roadmaps anticipating tandem commercialisation before 2030 and major PV manufacturers increasing investment in the technology, the focus is shifting from proving that tandems can achieve high efficiencies to determining which designs can be manufactured at scale and at competitive cost.
Perovskite/silicon tandems have emerged as a leading candidate. Much of the research to date has used silicon heterojunction (SHJ) as the bottom cell because of its high performance and ease of integration. But the industrial landscape has changed: TOPCon has rapidly become the dominant silicon cell technology in mass production.
The review asks whether TOPCon can now provide an industrial platform for tandem solar, benchmarking it against SHJ in terms of efficiency, cost, manufacturability and scalability. It examines how far TOPCon has closed the performance gap, what needs to be solved to integrate it successfully with perovskite cells, and whether its manufacturing advantages could ultimately translate into lower-cost electricity.
The review finds that TOPCon-based tandems still trail SHJ-based tandems in certified efficiency, but modelling suggests they could achieve comparable performance. Importantly, the analysis indicates that TOPCon may not need to match SHJ on efficiency to be commercially competitive. TOPCon's lower manufacturing costs could offset a modest efficiency gap.
Under the assumptions modelled in the review, a hypothetical 37% efficient TOPCon tandem could achieve a comparable levelised cost of electricity to a 38% efficient SHJ tandem. The finding highlights why efficiency alone does not determine which technology could ultimately succeed at scale.
The finding highlights why efficiency alone does not determine which technology could ultimately succeed at scale.
Combining diverse expertise to shape the future of ultra low-cost solar
The breadth of the review reflects the breadth of skill and perspectives within the collaboration. Led by Dr Rabin Basnet (ANU), the team combined expertise in TOPCon and tandem solar technology from ANU and the University of Melbourne, with UNSW expertise in techno-economic analysis, and perspectives from major global solar manufacturer Jinko Solar. An active developer of TOPCon technology, Jinko Solar provided insight into the industrial trajectory of the technology and the practical considerations involved in moving tandem concepts towards commercialisation.
“ACAP has built deep connections across the nodes at ANU, UNSW and the University of Melbourne, which has enabled this broader perspective on the future directions of silicon-based tandem technology,” said Professor Dan Macdonald (ANU). “By publishing this work together with our industry partners at Jinko Solar, we aim to provide a balanced and practical outlook on this important topic.”
The researchers looked beyond cell efficiency alone, examining how performance, manufacturing costs, scalability and long-term performance could shape the commercial potential of TOPCon-based tandems.
UNSW’s Dr Nathan Chang said,“The techno-economic framework highlights that the levelised cost of electricity of different technology alternatives is sensitive to expectations around future efficiency, cost, and degradation.”
What are the next research priorities for scalable tandem solar cells?
The review identifies the research priorities needed to improve TOPCon-based tandems, including capturing more sunlight, improving the connection between the two cells, protecting performance during manufacturing, and improving reliability and scalability while keeping costs low. Although focused on perovskite/silicon tandems, the findings have relevance for other silicon-based tandem technologies.
The review's findings demonstrate ACAP's value in bringing together the scientific, economic and industrial perspectives needed to identify the technologies and research priorities that can shape the future of high-efficiency, ultra-low-cost solar.
Reference: Basnet, R., Yang, Z., Ahmad, V., Chang, N., Fong, K., Yan, D., Wang, J., Xu, M., Yang, Jie., Zhang, X., Jin, H., Bullock, J., Weber, K., Shen, H. & Macdonald, D. (2026). TOPCon-based bottom cells for perovskite/silicon tandem solar cells. Joule 10(4), 102396.
Comments