Advancements In TOPCon Solar Cells

Researchers at the Chinese Academy of Sciences & Zhejiang University have developed a TOPCon bottom cell that improves perovskite solar cells, making them more efficient.

Silicon solar cells are gaining significant traction in the photovoltaic industry, drawing widespread interest due to their promising future. Specifically, silicon solar cells equipped with tunnel oxide passivating contact (TOPCon) structures are emerging as a leading technology in photovoltaics. This is attributed to their exceptionally high power conversion efficiency (PCE), cost-effectiveness, and scalability in mass production.

Researchers at the Ningbo Institute of Materials Technology and Engineering (NIMTE) of the Chinese Academy of Sciences (CAS), in collaboration with a team from Zhejiang University, have successfully developed a highly passivated TOPCon bottom cell. This innovation has led to the creation of perovskite/silicon tandem solar cells (TSCs) that boast high open-circuit voltages (VOCs) and outstanding efficiencies.

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Several flaws at the delicate silicon oxide/c-Si interface and inadequate field-effect passivation on textured substrates diminish the VOCs of current TOPCon silicon solar cells, thereby restricting their use in high-performance TSCs.

In this research, the team developed highly passivated p-type TOPCon structures and double-sided TOPCon bottom cells on industrial textured wafers using methods compatible with existing industry processes, such as ambient-pressure thermal oxidation and in situ plasma-enhanced chemical vapour deposition.

Refining the oxidation conditions, enhancing boron in-diffusion, and optimising aluminium oxide hydrogenation significantly enhanced the passivation quality of the newly prepared p-type TOPCon structures.

The sample with these optimised p-type TOPCon structures exhibited an improved implied open-circuit voltage (iVOC) of 715mV, outperforming traditional models.

The open-circuit voltages of the completed double-sided textured TOPCon bottom cells increased from 690mV to 710mV, setting new standards in the TOPCon bottom cell industry.

By combining the newly developed TOPCon bottom cells with perovskite top cells, the resulting TSCs attain remarkable VOCs of 1.9 V and a PCE of 28.2%. These results place them among the top-performing 1cm^2 n-i-p type monolithic perovskite/silicon TSCs.

This achievement underscores the extensive application possibilities of highly passivated TOPCon bottom cells in tandem devices and highlights their potential for future commercialization.

Reference: Zetao Ding et al, Highly passivated TOPCon bottom cells for perovskite/silicon tandem solar cells, Nature Communications (2024). DOI: 10.1038/s41467-024-52309-2