Researchers from the National University of Singapore (NUS), the Solar Energy Research Institute of Singapore (SERIS), and Chinese solar module maker JinkoSolar have achieved a power conversion efficiency of 32.76% for a perovskite-silicon tandem solar cell based on a TOPCon bottom device.
The result was certified by China's National Photovoltaic Industry Metrology Test Center (NPVM).
The research team noted that the current industrial standard TOPCon silicon wafers, with a thickness of around 130 µm, have reduced thermal mass and higher thermal conductivity. “During the perovskite annealing process, rapid heat transfer causes the perovskite layer to crystallize too quickly and uncontrollably, leading to voids and severe defects in the film, which compromise tandem performance,” JinkoSolar researcher Menglei Xu told pv magazine. “To overcome this bottleneck, we established a collaborative research effort with NUS and SERIS, innovatively developing a novel crystallization control strategy for the top perovskite cell.”
The team shifted from traditional strategies focused on inorganic lead ions and developed an approach specifically targeting the organic components. They introduced a 2-mercaptobenzothiazole (MBT) ligand into the precursor solution used for the perovksite film.
“The MBT ligand features dual-mode binding ability—specifically the heterocyclic N atom and the thiol (-SH) group—that enable simultaneous hydrogen bonding and electrostatic interaction with FA cations,” Xu explained. “This dual-mode interaction effectively stabilizes the intermediate phases, retarding the crystallization process to form a compact, void-free, and uniform high-quality perovskite film on industrial silicon wafers.”
The top perovskite cell was fabricated with a substrate made of indium tin oxide (ITO), a hole transport layer (HTL) based on nickel oxide (NiOₓ), a self-assembled monolayer (SAM), a perovskite absorber, the proposed surface treatment, an electron transport layer (ETL) made of thermally evaporated buckminsterfullerene (C60), a tin oxide (SnO2) layer, and another ITO layer.
The bottom silicon cell was fabricated entirely using industrially viable TOPCon processes on commercial Czochralski monocrystalline silicon wafers measuring approximately 182.3 mm × 183.75 mm with a thickness of 130 µm.
Tested under standard illumination conditions, the 0.925 cm² tandem device achieved a power conversion efficiency of 33.62% and an open-circuit voltage as high as 1.97 V. Furthermore, the cell retained 91% of its initial efficiency after 1,700 hours of continuous operation under maximum power point tracking (MPPT) at room temperature and 85% relative humidity.
“This is among the highest reported certified stabilized efficiencies for monolithic perovskite/TOPCon tandem solar cells,” the research group emphasized.
Regarding commercial compatibility, the study highlights the potential for seamless integration with existing industrial production lines. The researchers pointed out that this organic control strategy introducing the MBT ligand can be directly applied to large-area, high-throughput solution processing workflows, paving the way for integrating highly efficient perovskite technology into mainstream silicon production lines.
The solar cell was introduced in “Additive-assisted perovskite crystallization on industrial TOPCon silicon for tandem solar cells with improved efficiency,” published in nature energy.
“This work uncovers a previously overlooked perovskite crystallization issue on industrial silicon wafers, providing critical insights for integrating perovskite solar cells into mainstream TOPCon technology,” Xu concluded. “Notably, the strategy outlined in the paper holds significant potential for direct application in industrial production. Its compatibility with scalable, high-throughput solution processing methods paves the way for translating this research into practical industrial use.”
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