Unveiling the Effect of Synthetic Atmospheric Humidity on the Performance of FAPbBr₃ Nanocrystals and Their PeLEDs

The polar solvent of water can disrupt the structure of lead halide perovskite nanocrystals (PeNCs), and its presence is inevitable during the synthesis process. Therefore, it is crucial to understand the impact of synthetic atmospheric humidity on the performance of PeNCs and their electroluminescence. In this study, we first synthesized formamidine lead bromide (FAPbBr3) PeNCs at different relative air humidities and explored their optoelectronic properties and electroluminescence. We found that under optimal humidity conditions (40% R.H.), water molecules can reduce the nucleation growth barrier of PeNCs through ligand replacement. This process results in nanocrystals with good crystallinity and fewer defects, thereby reducing defect states and nonradiative recombination. The perovskite light-emitting diodes (PeLEDs) based on these FAPbBr3 PeNCs exhibit a maximum luminance of 39,000 cd m–2 and a peak external quantum efficiency of 16.2%, surpassing most reported values in the literature without the use of any additional additives. This study elucidates the role of atmospheric humidity in the growth of PeNCs and introduces the concept of humidity-assisted synthesis, which is crucial for scaling up production in the industry.