<p>Quantum dot light-emitting diodes (QLEDs) are emerging as a leader in next-generation display technology. In principle, the efficiency of QLEDs is highly reliant on the radiative recombination rate of injected electrons and holes in the QD emissive layer. Within a solitary light-emitting cycle, a pre-negative-charged QD bursts into a fleeting sparkle upon encountering a hole, much like a lighted piston within a roaring engine. More pistons bring higher horsepower. The challenge of achieving highly efficient QLED lies in how to increase the number of pre-negatively charged QDs. To address these limitations, we developed a ZnO@ZnMgO core-shell nanoparticle (NP)-based electron transport layer (ETL). This design synergistically combines the high conductivity of ZnO core and the low defect density of the ZnMgO shell. Measured by electron-excited transient absorption, the average electron population (&lt;<i>N</i><sub>e</sub>&gt;) in the emissive layer for ZnO@ZnMgO and ZnMgO-based QLEDs was 0.61 and 0.33 at 4 V, respectively, which greatly increases the carrier recombination efficiency. As a result, green QLEDs achieve a peak EQE of 30.66%, maximum luminance of 1,615,039.85 cd/m<sup>2</sup>, and a low turn-on voltage of approximately 2 V. The <i>T</i><sub>95</sub> operational lifetime exceeded 29,000 h at 1,000 cd/m<sup>2</sup>. Currently, all parameters are at the top level within the QLED region.</p>

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Improving average electron population in quantum-dot emissive layer via core-shell ZnO@ZnMgO nanoparticles for QLEDs with efficiency exceeding 30%

  • Han Zhang,
  • Weipeng Liu,
  • Xiaosuo Wang,
  • Leilei Zhao,
  • Chenyang Wang,
  • Xiangtong Zhang,
  • Huaibin Shen

摘要

Quantum dot light-emitting diodes (QLEDs) are emerging as a leader in next-generation display technology. In principle, the efficiency of QLEDs is highly reliant on the radiative recombination rate of injected electrons and holes in the QD emissive layer. Within a solitary light-emitting cycle, a pre-negative-charged QD bursts into a fleeting sparkle upon encountering a hole, much like a lighted piston within a roaring engine. More pistons bring higher horsepower. The challenge of achieving highly efficient QLED lies in how to increase the number of pre-negatively charged QDs. To address these limitations, we developed a ZnO@ZnMgO core-shell nanoparticle (NP)-based electron transport layer (ETL). This design synergistically combines the high conductivity of ZnO core and the low defect density of the ZnMgO shell. Measured by electron-excited transient absorption, the average electron population (<Ne>) in the emissive layer for ZnO@ZnMgO and ZnMgO-based QLEDs was 0.61 and 0.33 at 4 V, respectively, which greatly increases the carrier recombination efficiency. As a result, green QLEDs achieve a peak EQE of 30.66%, maximum luminance of 1,615,039.85 cd/m2, and a low turn-on voltage of approximately 2 V. The T95 operational lifetime exceeded 29,000 h at 1,000 cd/m2. Currently, all parameters are at the top level within the QLED region.