An HBr‐assisted slow cooling method is developed for the growth of centimeter‐sized Cs4PbBr6 crystals. The obtained crystals show strong green photoluminescence with absolute photoluminescence quantum yields up to 97%. More importantly, the evolution process and structural characterizations support that the nonstoichiometry of initial Cs4PbBr6 crystals induce the formation of nanosized CsPbBr3 nanocrystals in crystalline Cs4PbBr6 matrices. Furthermore, high efficiency and wide color gamut prototype white light‐emitting diode devices are also demonstrated by combining the highly luminescent Cs4PbBr6 crystals as green emitters and commercial K2SiF6:Mn4+ phosphor as red emitters with blue emitting GaN chips. The optimized devices generate high‐quality white light with luminous efficiency of ≈151 lm W−1 and color gamut of 90.6% Rec. 2020 at 20 mA, which is much better than that based on conventional perovskite nanocrystals. The combination of improved efficiency and better stability with comparable color quality provides an alternative choice for liquid crystal display backlights.
Perovskite quantum dots are emerging as attractive materials for photonic and optoelectronic applications. Patterning is an important step to incorporate them into display, anti‐counterfeiting, and optical chip applications. In this work, an in situ inkjet printing strategy is demonstrated for fabricating perovskite quantum dots patterns by printing perovskite precursor solutions onto a polymeric layer. Importantly, this strategy can achieve bright photoluminescence with a quantum yield up to 80% and shows broad applicability to a variety of perovskites and polymers. Moreover, the as‐fabricated perovskite quantum dots patterns are composed of a microdisks array on the surface of polymeric layer. The size of these microdisks can be varied by adjusting the printing temperature. To demonstrate the potential use in display and advanced anti‐counterfeiting applications, color pixel patterns and 2D code pattern are fabricated by varying the precursor solutions. The combination of superior photoluminescence properties, simple process, and low cost makes the in situ inkjet printing strategy very promising for patterning perovskite quantum dots toward photonic integrations.
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