Search

Controlled nucleation and slow growth endow blue emitting CsPbX3 nanocrystals (NCs) with bright photoluminescence (PL), which is crucial needed in luminescent devices. In this paper, a low‐temperature injection synthesis method is developed to control nucleation and the growth process by decreasing the reaction rate of ions, thereby controlling the morphologies of CsPbX3 NCs in clusters, nanorods (NRs), nanoplates (NPLs), and nanocubes by adjusting precursors, ligands, and injection parameters. CsPbX3 NCs exhibit excellent PL properties such as high quantum confinement effect. The PL peak wavelengths of CsPbBr3 NPLs and NRs are at 451 and 467 nm, respectively, in which their full width at half maximum (FWHM) of PL spectra is 22 and 12 nm, while their PL efficiencies are 65 and 74%, respectively. The method is further used to create CsPbI3 and CsPbCl3. CsPbI3 NPLs and NRs reveal PL peaks at 590 and 600 nm and PL efficiencies of 56% and 60%, respectively. These NCs exhibit excellent stability against ultraviolet light irradiation. A color conversion layer for white light‐emitting diodes is fabricated using these highly bright NCs. A Commission Internationale d'Eclairage color coordinate of (0.31,0.33) is located at the white light region specified by Rec.2020 standard, and the color temperature reaches 6189 K. [ABSTRACT FROM AUTHOR]

Quantum dots (QDs), with their exceptional optical properties, have emerged as promising candidates to replace traditional phosphors in lighting and display technologies. This study delves into the integration strategies of QDs within glass and polymer matrices to engineer advanced quantum dot color converters (QDCCs) at the industrial scale for practical applications. To achieve enhancements in the photostability and thermal stability of QDCCs, we explore two distinct approaches: the dispersion of QDs in a hydrophilic glass matrix via a sol–gel process and the incorporation of QDs into a non-polar acrylate monomer to formulate QD/polymer nanocomposites. This research further investigates the optical behaviors of these composites, focusing on their light-scattering and propagation mechanisms, which are critical for optimizing light extraction efficiency in QDCCs. Additional optical film and light-scattering particles can improve color conversion efficiency by ~140%. These advancements present a significant step forward in the development of high-performance, energy-efficient, QD-based lighting and display systems. [ABSTRACT FROM AUTHOR]

A feasible method to improve the charge balance of electroluminescent (EL) quantum dot (QD) light-emitting diodes (QLEDs) fabricated in the atmosphere is first demonstrated. Sodium chloride (NaCl) is introduced to poly-(vinylcarbazole) (PVK), a conventional hole-transport layer (HTL), which exhibits enhanced hole mobility. According to the electronic current mapping of the NaCl-doped PVK film, it is proven that NaCl can locally increase the current density of PVK films. The photoluminescence quantum yield (PLQY) of QDs on a PVK:NaCl film also increases by 25.1% (∼11.3%) compared with those coated on pure PVK film. The introduction of NaCl to atmosphere-process-based EL QLEDs significantly increases the current efficiency by ∼53% and elongates the operation stability by ∼275%, compared with that with pure PVK, which is ascribed to improved hole mobility, leading to more efficient carrier recombination in the NaCl-doped QLED devices. [ABSTRACT FROM AUTHOR]

Spinodal decomposition-based micro phase separation was found in a hybrid poly(9,9-dioctylfluorene-alt-N-(4-sec-butylphenyl)-diphenylamine) (TFB) and polyvinylcarbazole (PVK) system, which is used as a hole transporting layer (HTL) in atmosphere-based quantum dot (QD) light-emitting diodes (QLEDs). The micro phase separation could occur in some TFB–PVK hybrid films, leading to unexpected leakage current and poor carrier transport for the devices. A phase diagram based on the thermodynamic Flory–Huggins solution theory was established to clarify that the phase separation is based on spinodal decomposition, which is a rapid and spontaneous segregation of a single thermodynamic phase into two more stable phases without nucleation. This model clearly illustrates the hybrid TFB–PVK HTL system, showing that a hybrid polymer HTL without phase separation could significantly improve the device properties for atmosphere-based QLEDs on a glass substrate, e.g., decreased turn-on voltage by ∼47% (∼3.1 V) and increased brightness by ∼37% (∼276 000 cd m−2). Flexible atmosphere-based QLEDs with a hybrid HTL on polyimide substrates show similar results, i.e., decreased turn-on voltage by ∼30% and increased brightness by ∼133% (∼72 000 cd m−2). [ABSTRACT FROM AUTHOR]

Because of their inherent ionic properties, inorganic cesium halide lead perovskite nanocrystals (NCs) are normally unstable in light and heat environments as well as polar solvents, which seriously limit their practical application. In this paper, AlO(OH) nanosheets were assembled into hollow mesoporous spheres to encapsulate CsPbX3 NCs for increasing stability according to the powerful adsorption of AlO(OH) on Pb ions. The hollow AlO(OH) assemblies were created via hydrothermal synthesis. The in situ growth of CsPbX3 NCs in AlO(OH) assemblies was then finished in dimethylformamide solutions. After encapsulation, the stability of the NCs was greatly improved and the exchange reaction of halogen ions was effectively prevented. The NCs in the assemblies exhibited high PL quantum yields (PLQYs). Namely, blue-, green-, and red-emitting CsPbX3 (X = Cl, Br, and I)@AlO(OH) composites were fabricated. The composites were further mixed with polystyrene (PS) to prepare a flexible photoluminescent (PL) film with excellent bendable and foldable properties. The initial PLQYs of blue-, green-, and red-emitting CsPbX3@AlO(OH) composites were found to be 48.2, 96.4, and 43.7%, respectively. The films revealed high stability against water because of the excellent hydrophobic properties of PS. These emitting films were made into bands of various shapes, in which their well-flexible nature endowed the films with important applications. [ABSTRACT FROM AUTHOR]

See‐through double‐side‐emitting electroluminescent quantum‐dot light‐emitting‐diodes (QLEDs) with highly transparent tri‐layer MoO3/Ag:Cu/MoO3 electrode is demonstrated in this study. The tri‐layer MoO3/Ag: Cu/MoO3 electrode is prepared by a thermal co‐evaporation process, in which MoO3 is utilized as both a seed layer and a capping layer. This tri‐layer structure improves the transmittance as high as ≈88% and ≈86% for pure Ag and Ag:Cu at 550 nm, respectively. It is also found that minor Cu doping significantly improves the thermal stability and sheet resistance of Ag film. With the see‐through tri‐layer film as a device cathode, transparent double‐side‐emitting green QLED exhibits remarkable high brightness of 225, 500 cd m−2, the current efficiency of 58.68 cd A−1, the external quantum yield of 16.70%, and transmittance of 77% at 550 nm without any additional anti‐reflection coating. [ABSTRACT FROM AUTHOR]

Lead-halide perovskite nanocrystals (NCs), such as red-emitting CsPbI3, have gained significant attention due to their promising applications such as display backlights, light-emitting devices, and lasers. However, it is still a great challenge to stabilize CsPbI3 NCs and further tune and optimize their luminescence properties. In this study, effective Zn-derived ligand engineering was successfully conducted to create highly stable and bright CsPbI3 NCs for LEDs. The phase stability of CsPbI3 NCs at room temperature was improved by Zn ion-derived 1-dodecanethiol (DDT) ligand engineering, in which the ratios of Zn/DDT play an important role. Under optimized conditions, the as-treated CsPbI3 NCs were well dispersed and revealed uniform size distribution and a high photoluminescence (PL) quantum yield of 95.4%. In addition, the treated CsPbI3 NCs retained the initial PL efficiency after being stored at room temperature for more than 100 days. No phase change occurred for the NCs under UV light irradiation and thermal cycling conditions. Finally, these CsPbI3 NCs were used for white light-emitting diodes, which had advantages in a wide color gamut and good stability. [ABSTRACT FROM AUTHOR]