Triple‐Cation Engineering for Efficient and Stable Sky‐Blue Quasi‐2D Perovskite LEDs

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Abstract
Quasi‐2D metal‐halide perovskite LEDs (PeLEDs) are promising for displays but remain limited by trap‐mediated loss and short lifetimes, especially in the blue. Here, we report a triple‐cation A‐site doping strategy by co‐incorporating Rb + and guanidinium (GA + ) with Cs + to simultaneously improve efficiency and stability. Rb + contracts the lattice and extends the radiative lifetime, whereas GA + predominantly passivates surface and interfacial defects and moderates the quasi‐2D phase distribution. Together they extend photoluminescence lifetimes and suppress trap‐assisted nonradiative pathways, as confirmed by time‐resolved photoluminescence and trap analyses. We further augment the device performance by a yttrium additive and a modified hole‐injection layer. The optimized sky‐blue devices achieve an external quantum efficiency of 9.0% at 492 nm and the operating lifetime ( T 50 ) over 18 min at 100 cd m −2 . This synergy between A‐site alloying, additive engineering, and HTL modification provides a practical route toward efficient, more stable sky‐blue quasi‐2D PeLEDs.
Funding Information
  • Hong Kong University of Science and Technology (IRS22SC117)
  • Hong Kong University of Science and Technology (DG24SC01)
  • University Research Committee, University of Hong Kong (GRF#16306020)

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