Implementing QD-In-Host Structure for High Efficiency in Deep-Blue Perovskite LEDs

Metal halide perovskite light-emitting diodes (PeLEDs) have recieved substantial interest due to their exceptional color purity, satisfying the Rec. 2020 color gamut standard, and impressive efficiency in pure-green and pure-red perovskite nanoparticle LEDs. However, the challenge lies in achieving high efficiency in the deep-blue region, an area hitherto under-explored. This study focuses on using CsPbBr₃ quantum dots (QDs) as the light-emitting layer in PeLEDs. We identify two obstacles that need to be overcome: the difficulty in ligand post-treatment and the spectrum red-shift in the film state.<br/>Here, we propose an alternative ligand enriched with a chemical passivation process, effectively amplifying the photoluminescence quantum yield (PLQY) of deep-blue QDs from 15% to nearly 90%. Furthermore, to address the spectrum red-shift induced by energy transfer or electronic coupling, we introduce a QD-in-host structure to physically sperate the QDs in the film state. A reduction in the concentration of QDs in the film yielded a blue-shift of approximately 7 nm in the emission spectrum. By incorporating these strategies, we achieved a maximum external quantum efficiency of 6.2% at a peak wavelength of 462 nm. The findings of this study provide crucial strategies for deep-blue QD PeLEDs, which hold potential for broad applicability across diverse PeLED types.