PolyU research overcomes major obstacle to solar technology development, achieving record 33.89% power-conversion efficiency in solar cells

Significantly surpassing their single-junction counterparts in power-conversion efficiency (PCE), two-terminal perovskite/silicon tandem solar cells have emerged as a game-changer in photovoltaics. However, due to the lack of effective optimisation of the device interface to maximise charge extraction efficiency and reduce energy loss, their widespread application has been limited. Researchers of The Hong Kong Polytechnic University (PolyU) have pioneered a novel bilayer interface passivation strategy to develop tandem solar cells that achieve a record-high PCE of 33.89%, representing a milestone in the development of solar technology.

Interfacial recombination at the perovskite/electron transport layer interface has long been considered a major obstacle to enhancing the efficiency of perovskite/silicon tandem solar cells. Prof. YIN Jun, Assistant Professor of the Department of Applied Physics at PolyU, and his research team have made a breakthrough in interface engineering towards addressing this critical challenge. They have integrated advanced material design and a device optimisation strategy to develop high-efficiency perovskite/silicon tandem devices. This research was conducted in partnership with LONGI Green Energy Technology Co. Ltd and Soochow University. The findings have been published in the international journal Nature.

The team introduced a nanoscale, discretely distributed ultrathin lithium fluoride (LiF) layer combined with a short-chain ethylenediammonium diiodide (EDAI) molecule deposition, inducing field-effect and chemical passivation simultaneously and thereby achieving a bilayer-intertwined passivation. This strategy significantly improved electron extraction and effectively suppressed non-radiative recombination. The researchers then applied the strategy to perovskite stacked on a double-textured silicon heterojunction cell, which featured a mildly textured front surface and a heavily textured rear surface, and successfully constructed the perovskite/silicon tandem devices. This unique design can enhance photocurrent while also maintaining robust rear passivation, effectively optimising both light absorption and power transfer.

The resulting perovskite/silicon tandem solar cells have achieved an independently certified PCE of 33.89%, marking the first reported certified efficiency of a two-junction solar cell that exceeds the single-junction Shockley-Queisser limit of 33.7%. In addition to their record-breaking efficiency, the cells demonstrate an impressive fill factor of 83%, an open-circuit voltage approaching 1.97 V, as well as significantly improved long-term stability. 

This breakthrough helps overcome long-standing efficiency barriers to improving power-conversion efficiency of solar cells and unlocks the application potential of perovskite technologies in photovoltaics. It also serves as a strong motivation for continued innovation and advancement in solar technology, ultimately contributing to a more sustainable and energy-efficient future.

Prof. Yin said, “Our research is driven by the vision of breaking traditional efficiency barriers in solar cells. By integrating advanced materials like perovskites with established silicon technologies, we harness the best of both worlds to redefine solar cell performance. This multidisciplinary approach not only showcases the tremendous potential of photovoltaic technology, but also lays a solid foundation for the development of renewable energy and new quality productive forces.”

Prof. Yin has been awarded the Excellent Young Scientists Fund for 2024 by the National Natural Science Foundation of China for his outstanding contributions to materials science. Moving forward, he and his research team will continue to explore the optoelectronic properties of advanced perovskite materials and their applications in next-generation photovoltaic devices.

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