Perovskite light‐emitting diodes (PeLEDs) are strong candidates for next‐generation display and lighting technologies due to their high color purity and low‐cost solution‐processed fabrication. However, PeLEDs are not superior to commercial organic light‐emitting diodes (OLEDs) in efficiency, as some key parameters affecting their efficiency, such as the charge carrier transport and light outcoupling efficiency, are usually overlooked and not well optimized. Here, ultrahigh‐efficiency green PeLEDs are reported with quantum efficiencies surpassing a milestone of 30% by regulating the charge carrier transport and near‐field light distribution to reduce electron leakage and achieve a high light outcoupling efficiency of 41.82%. Ni0.9Mg0.1Ox films are applied with a high refractive index and increased hole carrier mobility as the hole injection layer to balance the charge carrier injection and insert the polyethylene glycol layer between the hole transport layer and the perovskite emissive layer to block the electron leakage and reduce the photon loss. Therefore, with the modified structure, the state‐of‐the‐art green PeLEDs achieve a world record external quantum efficiency of 30.84% (average = 29.05 ± 0.77%) at a luminance of 6514 cd m−2. This study provides an interesting idea to construct super high‐efficiency PeLEDs by balancing the electron‐hole recombination and enhancing the light outcoupling.
Mini-LED backlights, combining color conversion materials with blue mini-LED chips, promise traditional liquid crystal displays (LCDs) with higher luminance, better contrast, and a wider color gamut. However, as color conversion materials, quantum dots (QDs) are toxic and unstable, whereas commercially available inorganic phosphors are too big in size to combine with small mini-LED chips and also have strong size-dependence of quantum efficiency (QE) and reliability. In this work, we prepare fine-grained Sr2Si5N8:Eu2+-based red phosphors with high efficiency and stability by treating commercially available phosphors with ball milling, centrifuging, and acid washing. The particle size of phosphors can be easily controlled by milling speed, and the phosphors with a size varying from 3.5 to 0.7 μm are thus obtained. The samples remain the same QE as the original ones (∼80%) even when their particle size is reduced to 3.2–3.5 μm, because they contain fewer surface suspension bond defects. More importantly, SrBaSi5N8:Eu2+ phosphors show a size-independent thermal quenching behavior and a zero thermal degradation. We demonstrate that red-emitting mini-LEDs can be fabricated by combining the SrBaSi5N8:Eu2+ red phosphor (3.5 μm in size) with blue mini-LED chips, which show a high external quantum efficiency (EQE) of above 31% and a super-high luminance of 34.3 Mnits. It indicates that fine and high efficiency phosphors can be obtained by the proposed method in this work, and they have great potentials for use in mini-LED displays.
Pure red mixed halide CsPbBr3-xIx perovskite nanocrystals (NCs) exhibit a high photoluminescence quantum yield (PLQY) and narrow full width at half maximum (FWHM), but there are phase stability issues that...
Lead halide perovskite nanocrystals (NCs) have been the star material in lighting and displays owing to their excellent photoelectrical properties, but they have not simultaneously realized high photoluminescence quantum yield (PLQY) and high stability.To solve this problem, we propose a perovskite/linear low-density polyethylene (perovskite/LLDPE) core/shell NC by the synergistic role of the pressure effect and steric effect. Green CsPbBr 3 /LLDPE core/shell NCs with near-unity PLQY and nonblinking behavior were synthesized through an in situ hot-injection process. The mechanism of the improved photoluminescence (PL) properties is the enhanced pressure effect resulting in increased radiative recombination and interaction between the ligand and perovskite crystals, as confirmed by the PL spectra and finite element calculations. Meanwhile, the NCs show high stability under ambient conditions (with a PLQY of 92.5% after 166 days) and against 365 nm UV light (maintaining 61.74% of the initial PL intensity after continuous radiation for 1000 min). This strategy also works well in the blue and red perovskite/LLDPE NCs and red InP/ZnSeS/ZnS/LLDPE NCs. Finally, white-emitting Mini-LEDs were fabricated by combining the green CsPbBr 3 /LLDPE and red CsPbBr 1.2 I 1.8 /LLDPE core/shell NCs with blue Mini-LED chips. The white-emitting Mini-LEDs exhibit super wide color gamut (∼129% of the National Television Standards Committee or 97% of the Rec. 2020 standards).
Quasi‐2D Dion‐Jacobson (DJ) perovskites are promising candidates for fabricating high‐performance blue‐emitting perovskite light‐emitting diodes (PeLEDs) because of their strong quantum/dielectric confinement and high stability. However, obtaining high‐efficiency blue PeLEDs based on DJ perovskites remains a major challenge. Herein, sky‐blue DJ perovskites are synthesized by using 1,8‐diamino‐3,6‐dioxaoctane as an organic diamine and high‐quality perovskite films are prepared by incorporating poly(vinylidene fluoride‐co‐hexafluoropropylene) (PVDF‐HFP) as an additive, aiming to improve the photoluminescence quantum yield and electron carrier mobility of the film used as an emissive layer in PeLEDs. Finally, sky‐blue PeLEDs using PVDF‐HFP‐modified DJ perovskite films are demonstrated to show a high maximum external quantum efficiency of 16.55%. A promising strategy is provided to design high‐quality perovskite films for constructing high‐performance blue PeLEDs.
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