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The US National Renewable Energy Laboratory (NREL) has achieved remarkable efficiency and stability in a broadband perovskite tandem solar cell. The scientists developed the device with an inverted architecture and used gaseous cooling instead of an antisolvent in the manufacturing process.
NREL researchers have fabricated an all-perovskite tandem solar cell with perovskite films that show reduced defect density and achieve a power conversion efficiency of 27.1%.
The new cell is based on another inverted perovskite solar cell made with a pin structure, which was presented by the research group in September. This device, according to the scientists, was able to maintain 87% of its original efficiency after 2,400 hours of operation at 55ºC.
For the new cell, the group did not use an antisolvent to create a uniform perovskite film and instead used gas quenching, which involves rapidly cooling parts of a material from the critical temperature to make them stronger and harder. It is often used to maintain the properties associated with a crystalline structure or a phase distribution.
"The result solved the problem of the separation of bromine and iodine, giving rise to a perovskite film with better structural and optoelectronic properties," the scientists explained. “The gas quenching process, when applied to high bromine perovskite chemicals, forces the crystals to grow together, tightly packed from top to bottom, so that they become a single grain and significantly reduces the number of defects".
Using this method, the researchers achieved 20% efficiency for the broadband layer, which also showed operational stability, with less than 5% degradation over 1,100 hours.
When connected to a narrow band lower 1.25 eV perovskite cell, the perovskite layer was able to raise the overall efficiency of the cell to 27.1% and its open circuit voltage to 2.2 V.
“The gas quenching method is a general way to improve the performance of broadband perovskite solar cells,” the scientists say.
They presented the cell technology in “ Compositional texture engineering for highly stable wide-bandgap perovskite solar cells ,” recently published in Science.
“The new growth method demonstrated the potential of high-performance all-perovskite tandem devices and prompted the development of other perovskite-based tandem architectures, such as those incorporating silicon,” they concluded. |
