Tunability of emitting colors of perovskite quantum dots (PQDs) was generally realized via composition/size modulation. Due to their bandgap absorption and ionic crystal features, the mixing of multiple PQDs inevitably suffers from reabsorption and anion-exchange effects. Herein, we address these issues with high-content Mn-doped CsPbCl PQDs that can yield blue-excitable orange Mn emission benefited from exciton-to-Mn energy transfer and Cl-to-Br anion exchange. Silica-coating was applied to improve air stability of PQDs, suppress the loss of Mn, and avoid anion-exchange between different PQDs. As a direct benefit of intense multicolor emissions from Mn-doped PQD@SiO solid phosphors, a prototype white light-emitting diode with excellent optical performance and superior light stability was constructed using green CsPbBr@SiO and orange Mn: CsPb(Cl/Br)@SiO composites as color converters, verifying their potential applications in the field of optoelectronics.
Graphitic carbon nitride (g-C 3 N 4 ) is a promising photocatalyst for solar H 2 generation, but the practical application of g-C 3 N 4 is still limited by the low separation efficiency of photogenerated charge carriers. Herein, we report the construction of ternary g-C 3 N 4 /graphene/MoS 2 two-dimensional nanojunction photocatalysts for enhanced visible light photocatalytic H 2 production from water. As demonstrated by photoluminescence and transient photocurrent studies, the intimate two-dimensional nanojuction can efficiently accelerate the charge transfer, resulting in the high photocatalytic activity. The g-C 3 N 4 /graphene/MoS 2 composite with 0.5% graphene and 1.2% MoS 2 achieves a high H 2 evolution rate of 317 μmol h −1 g −1 , and the apparent quantum yield reaches 3.4% at 420 nm. More importantly, the ternary g-C 3 N 4 /graphene/MoS 2 two-dimensional nanojunction photocatalyst exhibits much higher photocatalytic activity than the optimized Pt-loaded g-C 3 N 4 photocatalyst.
As a novel type of promising materials, metal halide perovskites are a rising star in the field of optoelectronics. On this basis, a new frontier of zero-dimensional perovskite-related Cs4PbBr6 with bright green emission and high stability has attracted an enormous amount of attention, even though its photoluminescence still requires to clarification. Herein, the controllable phase transformation between three-dimensional CsPbBr3 and zero-dimensional Cs4PbBr6 is easily achieved in a facile ligand-assisted supersaturated recrystallization synthesis procedure via tuning the amount of surfactants, and their unique optical properties are investigated and compared in detail. Both Cs4PbBr6 and CsPbBr3 produce remarkably intense green luminescence with quantum yields up to 45% and 80%, respectively; however, significantly different emitting behaviors are observed. The fluorescence lifetime of Cs4PbBr6 is much longer than that of CsPbBr3, and photo-blinking is easily detected in the Cs4PbBr6 product, proving that the zero-dimensional Cs4PbBr6 is indeed a highly luminescent perovskite-related material. Additionally, for the first time, tunable emissions over the visible-light spectral region are demonstrated to be achievable via halogen composition modulations in the Cs4PbX6 (X = Cl, Br, I) samples. Our study brings a simple method for the phase control of CsPbBr3/Cs4PbBr6 and demonstrates the intrinsic luminescence nature of the zero-dimensional perovskite-related Cs4PbX6 products.
Full-color visible emissions are particularly crucial for applications in displays and lightings. In this work, we developed a facile room-temperature ligand-assisted supersaturated recrystallization synthesis of monodisperse, cubic structure CsFAPbX (X = Cl, Br, and I or their mixtures Cl/Br and Br/I, 0 ≤ m ≤ 1) hybrid perovskite quantum dots (QDs). Impressively, cation substitution of Cs by FA was beneficial in finely tuning the band gap and in exciton recombination kinetics, improving the structural stability, and raising the absolute quantum yields up to 85%. With further assistance of anion replacement, full-spectral visible emissions in the wavelength range of 450-750 nm; narrow full width at half-maxima, and a wide color gamut, encompassing 130% of National Television System Committee television color standard, were achieved. Finally, CsFAPbX-polymer films retaining multicolor luminescence are prepared and a prototype white light-emitting diode device was constructed using green CsFAPbBr and red CsFABrI QDs as color converters, certainly suggesting their potential applications in the optoelectronics field.
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