Room-Temperature Construction of Mixed-Halide Perovskite Quantum Dots with High Photoluminescence Quantum Yield

Abstract

All-inorganic cesium lead halide perovskite quantum dots (QDs) are attractive potential materials for high-performance optoelectronics because of their high photoluminescence quantum yield (PLQY), narrow emission widths, and tunable optical band gap. Hot injection is considered as a common method and is widely used for the preparation of the QDs. However, it suffers from the problems of time consumption and high cost for the mixed-halide CsPb(XY) 3 (XY is a combination of Cl and Br or Br and I) QDs because of its cumbersome preparation of precursors with different halide proportions. Here, the mixed-halide CsPb(XY) 3 QDs were synthesized by a simple and efficient way of mixing the single-halide CsPbX 3 (CsPbX 3 ; X = Cl, Br, and I) QDs stock solutions at room temperature. By modulating the ratio of stock solutions precisely, the cubic crystal structure of mixed-halide CsPb(XY) 3 QDs are obtained undergoing anion-exchange and lattice reconstruction processes. The roomtemperature construction of QDs showed excellent properties of bright PL with the emission peaks tunable over the entire visible light spectra, a narrow full width at half-maximum , and high PLQY, which compare favorably with the QDs prepared by the conventional hot-injection method. Furthermore, backlight light-emitting diodes (LEDs) were fabricated using the mixed-halide QDs cooperated with a commercial 365 nm PL emitting InGaN chip. The QD-assisted LEDs presented the pure and bright emission, as well as the long-term stability (∼3600 h) under an average relative humidity of 60%.

Aqueous Phase Exfoliating Quasi‐2D CsPbBr3 Nanosheets with Ultrahigh Intrinsic Water Stability

“…As shown in Figure d, the visibly increasing of short‐lived lifetime ratio (τ 1 %) at 48 h evidently demonstrates the water‐assisted exfoliation process of bulk‐like CsPbBr 3 NCs. Compared with other samples, its shoret‐lived lifetime (τ 1 ) also increases significantly (Table ), which further proving the increasing of surface state because the decay lifetime of surface‐state emission is longer than trap‐state emission 19a. Moreover, this exfoliation will increase the solution concentration, so the PL intensity can keep continuous enhancement (Figure a).…”

“…These time‐resolve PL decay curves can be fitted well with a biexponential function (Equation (1))where I ( t ) is time‐dependent PL intensity. τ 1 and τ 2 denote short‐lived and long‐lived decay lifetime, which correspond to the nonradiative recombination stemming from the trap‐state and the radiative recombination of intrinsic exciton respectively . The A 1 and A 2 constants can represent the proportion of each component.…”

“…To assess the water stability of quasi‐2D CsPbBr 3 NSs, we directly dispersed the quasi‐2D CsPbBr 3 NSs into water to monitor their PL spectra at different immersion time ( Figure a). For comparison, we prepared CsPbBr 3 QDs by conventional room‐temperature supersaturated recrystallization method 19a. These conventional CsPbBr 3 QDs were dissolved in toluene and placed on the top of water and saturated CsBr salt aqueous solution (maximizing the contribution of CsBr to water stability) respectively, and corresponding temporal evolution process of PL spectra were shown in Figure b and Figure S6 in the Supporting Information.…”

Oxalic Acid Enabled Emission Enhancement and Continuous Extraction of Chloride from Cesium Lead Chloride/Bromide Perovskite Nanocrystals

“…Alternatively, there may be a lattice reconstruction occurring in response to the extraction of chloride ions during and/or after the OxA treatment process . Raman measurements (Figure b; Figure S4f, Supporting Information) further revealed the advantages of the OxA treated samples even with a lower dosage treatment, as all of them possess stronger vibrational mode ν 1 at 72 cm −1 compared with the broader and weaker peak of the pristine sample, indicating less [PbX 6 ] 4− octahedra distortion in perovskite lattices based on the relevant literature …”

One‐Step Loading on Natural Mineral Halloysite Nanotube: An Effective Way to Enhance the Stability of Perovskite CsPbX3 (X = Cl, Br, I) Quantum Dots

“…Moreover, there is no difference in the XRD patterns of the CsPbBr 3 @HNTs sample at room temperature and heating at 120 °C (Figure b), indicating its excellent heat‐resistance performance. This superior stability is also remarkably higher than those of CsPbBr 3 QDs in other carriers such as CsPbBr 3 @SiO 2 (40%), CsPbBr 3 @zeolite‐Y (50%), and CsPbBr 3 @1‐tetra‐decylphosphonic acid (TDPA) composites (59%) . Thus, the complex and assembly of CsPbBr 3 QDs on HNTs could extremely improve the thermal stability.…”