We
present a novel composite strategy to enhance the stability
of water-sensitive CsPbBr3 quantum dots (QDs) by embedding
the QDs into the super-hydrophobic porous organic polymer frameworks
(CPB@SHFW). The CPB@SHFW composites not only preserve a high photoluminescence
quantum yield (PLQY ≈ 60%) and narrow band emission (full width
at half-maximum ≈ 16 nm) but also inherit the outstanding water-resistant
property of SHFW to protect the QDs from hydrolytic degradation. The
PLQY of the composites was maintained at 91% (PLQY ≈ 54.3%)
of the initial one (PLQY ≈ 60%) after being immersed in water
for 31 days. Even after being immersed in water for 6 months, the
CPB@SHFW composites still retain a bright green emission. In addition,
super-hydrophobic perovskite QD-polymer composites (IPQDs@SHFW) with
tunable and bright emission were prepared by using suitable halide
salts. A white light-emitting diode (WLED) device was prepared by
combining green-emitting CPB@SHFW composites and red-emitting K2SiF6:Mn4+ phosphors with a blue LED
chip. The device exhibits a high luminous efficiency of 50 lm/W and
a wide color gamut (127% of the National Television System Committee
and 95% Rec. 2020). This work provides an alternative approach to
solve the challenging stability issue of perovskite QDs; therefore,
it has a positive implication for their practical application in liquid
crystal display backlights.
The microscale composite structure strategy of embedding CsPbBr3 nanocrystals (NCs) in the microscale Cs4PbBr6 matrix (CPB113/CPB416) has successfully demonstrated its ability to resolve the fluorescence quenching of perovskite NCs in the solid agglomeration state due to the loss of quantum confinement. Unfortunately, the controllable synthesis of monodisperse nanoscale composites with bright emission in the solid state remains a great challenge. Here, we present for the first time a novel supersaturated recrystallization process to controllably synthesize monodisperse CPB113/CPB416 composite NCs with bright emission in the solid form, where CsPbBr3 NCs were uniformly embedded in the nano hexagonal Cs4PbBr6 matrix. The existence of 2-methylimidazole (MeIm) not only can control the composition rate of CsPbBr3 to Cs4PbBr6, the size and dispersity of CsPbBr3 in the composite NCs but can also help controllably obtain the monodisperse and hexagonal Cs4PbBr6 matrix. The as-prepared composite structure can effectively prevent CsPbBr3 fluorescence quenching and make the composite NCs have a high photoluminescence quantum yield (PLQY) of 83%. In addition, we obtained tunable blue to red emitting composite NCs by varying the halide salts.
Yb 3+ doped lead-free double perovskites (DPs) with near-infrared (NIR)emitting have attracted extensive attention due to their wide application prospects. Unfortunately, they still suffer from weak NIR emission due to undesirable resonance energy transfer between the sensitizers and Yb 3+ ions. Herein, a new effective NIR-emitting DP is developed by co-doping Sb 3+ and Yb 3+ into Cs 2 AgInCl 6 . Experiments and theoretical calculations reveal that induced by co-doping Sb 3+ ions, the self-trapped excitation (STE) emission intensity of Cs 2 AgInCl 6 is greatly enhanced by 240 times, and the STE emission shifts from 600 nm to 660 nm, which contributes to a larger spectral overlap between STE emission and the absorption of Yb 3+ ions. As a result, the absolute NIR photoluminescence quantum yield reaches an unprecedented 50% in lead-free DPs via high-efficiency STE sensitization (>30%). The excellent optical performance of Cs 2 AgInCl 6 : Sb, Yb with high ambient, thermal and light stability makes it suitable for application in night-vision devices. Moreover, an ingenious dual-modal optical information encryption based on the combination of visible and NIR fluorescence printing patterns utilizing Cs 2 AgInCl 6 : Sb and Cs 2 AgInCl 6 : Sb, Yb respectively is successfully demonstrated. This study provides inspiration for designing highly efficient NIR-emitting Ln 3+ -doped DPs and illustrates their great potential in versatile optoelectronic applications.
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