Recently, the pursuit of high photoluminescence quantum yields (PLQYs) for blue emission in perovskite nanocrystals (NCs) has attracted increased attention because the QY of blue NCs lags behind those of green and red ones severely, which is fatal for three-primary-color displays. Here, we propose an in situ PbBr 6 4− octahedra passivation strategy to achieve a 96% absolute QY for the ultrapure (line width = 12 nm) blue emission from CsPbBr 3 nanoplatelets (NPLs), and both values rank first among perovskite NCs with blue emission. From the aspect of constructing intact PbBr 6 4− octahedra, additional Br − was introduced to drive the ionic equilibrium to form intact Pb−Br octahedra. The reduced Br vacancy and inhibited nonradiative recombination processes are well proved by reduced Urbach energy, increased Pb−Br bonds, and slower transient absorption delay. Blue light-emitting diodes (LEDs) using NPLs were fabricated, and a high external quantum efficiency (EQE) of 0.124% with an emission line width of ∼12 nm was realized. This work will provide good references to break the "blue-wall" in perovskite NCs.
Understanding the subtle structure–property relationships of quantum dots (QDs) is essential for targeted modulation of optoelectronic properties, and the influences of surface defects of inorganic halide perovskite (HP) QDs are still not very clear. Here, the negative exciton trapping effects of surface halide vacancies (VX) on the photoluminescence quantum yield QY (PLQY) of HPQDs are determined by a detailed analysis of the optical parameters, exciton dynamics, and surface chemical states. Based on the fact that VX contribute greatly to nonradiative recombination processes, versatile in situ and postpassivation strategies are developed by constructing intact Pb–X octahedrons. High QYs for standard red CsPbBr1I2 (85%), green CsPbBr3 (96%), and blue CsPbBr1.3Cl1.7 (92%) emissions are achieved. The superiorities of the reduced VX are further demonstrated by high external quantum efficiency of 0.8% and a stable emission wavelength of the blue light‐emitting diodes. This study deepens the understanding of HPQDs and demonstrates the potential for the artificial control of the optical properties of HPQDs.
Copper halide Cs3Cu2X5 (X = Cl, Br, I) nanocrystals (NCs) have become a research hotspot in recent years. Compared with perovskite NCs, they have large stokes-shift with self-absorption-free effect and...
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