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, which 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.

中文翻译：

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自组装的分层纳米结构钙钛矿可通过能量级联实现高效LED †

金属卤化物钙钛矿已经确立了自己作为非凡的光电材料的地位，在大范围照明和显示器中的应用展现出了希望。然而，低发光，发光二极管（LED）的低效率以及复杂的制备方法目前限制了在应用方面的进一步进展。在这里，我们报道了一种新颖独特的介观膜结构，该结构具有3D甲form溴化铅（FAPbBr ₃）分级大小的纳米晶体，再加上八溴化铵溴化钙钛矿的微片，可实现能量级联，从而产生非常高性能的发光二极管，并在绿色光谱区域内进行发射。这些分级结构的钙钛矿膜表现出超过80％的光致发光量子产率，并且与创纪录的超过57.6 cd A ^-1的高效率相关的LED以及超过13％的外部量子效率。此外，由于低的开启电压（〜2.2 V），LED的功率效率超过了每瓦58流明，而无需任何光耦合结构。