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RESEARCH PRODUCT

Self-assembled hierarchical nanostructured perovskites enable highly efficient LEDs via an energy cascade

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Metal halide perovskites have established themselves as extraordinary optoelectronic materials, exhibiting promise for applications in large area illumination and displays. However, low luminescence, low efficiencies of the light-emitting diodes (LEDs), and complex preparation methods currently limit further progress towards applications. Here, we report on a new and unique mesoscopic film architecture featuring the self-assembly of 3D formamidinium lead bromide (FAPbBr3) nanocrystals of graded size, coupled with microplatelets of octylammonium lead bromide perovskites that enables an energy cascade, yielding very high-performance light-emitting diodes with emission in the green spectral region. These hierarchically structured perovskite films exhibit photoluminescence quantum yields of over 80% and LEDs associated with record high efficiencies in excess of 57.6 cd A−1 with an external quantum efficiency above 13%. Additionally, due to low turn-on voltages (~2.2 V) the LEDs have power efficiencies exceeding 58 lumens per Watt, obtained without any light-outcoupling structures. NRF (Natl Research Foundation, S’pore) MOE (Min. of Education, S’pore) Accepted version