Unveiling the\nEffect of Synthetic Atmospheric Humidity\non the Performance of FAPbBr<sub>3</sub> Nanocrystals and Their PeLEDs

The polar solvent of water can disrupt\nthe structure\nof lead halide\nperovskite nanocrystals (PeNCs), and its presence is inevitable during\nthe synthesis process. Therefore, it is crucial to understand the\nimpact of synthetic atmospheric humidity on the performance of PeNCs\nand their electroluminescence. In this study, we first synthesized\nformamidine lead bromide (FAPbBr<sub>3</sub>) PeNCs at different relative\nair humidities and explored their optoelectronic properties and electroluminescence.\nWe found that under optimal humidity conditions (40% R.H.), water\nmolecules can reduce the nucleation growth barrier of PeNCs through\nligand replacement. This process results in nanocrystals with good\ncrystallinity and fewer defects, thereby reducing defect states and\nnonradiative recombination. The perovskite light-emitting diodes (PeLEDs)\nbased on these FAPbBr<sub>3</sub> PeNCs exhibit a maximum luminance\nof 39,000 cd m<sup>–2</sup> and a peak external quantum efficiency\nof 16.2%, surpassing most reported values in the literature without\nthe use of any additional additives. This study elucidates the role\nof atmospheric humidity in the growth of PeNCs and introduces the\nconcept of humidity-assisted synthesis, which is crucial for scaling\nup production in the industry.