A research group, led by Prof. HAN Keli from the Dalian Institute of Chemical Physics of the Chinese Academy of Sciences, recently revealed the luminescence enhancement mechanism of a series of new lead-free quadruple halide perovskite nanocrystals, and prepared high-performance photodetectors.

The researchers reported a series of quadruple perovskite colloidal nanocrystals with ordered vacancies. By alloying Cs4MnBi2Cl12 nanocrystals, the fluorescence quantum yield could be increased by nearly 100 times.

Through carrier ultrafast dynamics studies, the researchers found that in the quadruple perovskite nanocrystals, free excitons were rapidly self-trapped as "self-trapped excitons," and a self-trapped exciton-assisted donor-acceptor (Mn2+) occurred energy transfer process. Alloying could eliminate the ultra-fast defect state trapping process that competed with energy transfer, and increase the crystallinity of the nanocrystals, thereby improving the luminous efficiency.

Based on the alloyed quadruple perovskite nanocrystals with high crystallinity and long carrier lifetime, the researchers prepared a photodetector, which had ultra-high responsivity. Its sensitivity was much higher than that of the previously reported photodetectors based on lead-free perovskite nanocrystals.

The study shows that the quadruple perovskite type nanocrystal opens up new possibilities for photovoltaic applications.

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