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A facile and reproducible method for scalable synthesis of high‐quality core/shell quantum dots (QDs) is a prerequisite to facilitate their versatile applications. Herein, a seed‐mediated heat‐up approach is developed for the preparation of high‐quality core/shell QDs with variable shell composition and continuously tunable shell thickness by selection of conventional salts as the precursors. The method is very simple and highly reproducible and, therefore, can be easily scaled up to get gram‐level product. The as‐obtained CdSe/CdS and CdSe/ZnCdS core/shell QDs exhibit intriguing optical properties, that is a narrow photoluminescence (PL) emission peak and near‐unity PL quantum yield. Importantly, the CdSe/ZnCdS core/shell QDs with a size of 11.4 nm exhibit obviously suppressed blinking behavior, and the fraction of nonblinking QDs (defined by an on‐time fraction ≥ 0.95) can reach as high as 96.0% on the measurement of more than 200 QDs. Moreover, quantum‐dot light‐emitting diodes (QLEDs) based on CdSe/ZnCdS core/shell QDs show a peak external quantum efficiency of 14.8% and low efficiency roll‐off at luminance ranging from 1000 to 25 000 cd·m−2. It is anticipated that the presented work will pave a novel way for the large‐scale production of high‐quality QDs and further boost their applications in light‐emitting diodes, lasing, and biological imaging. [ABSTRACT FROM AUTHOR]

Since the layer erosion often happens during the solution-processable optoelectronic devices, and thus the efficiency of inkjet-printed quantum dot light emitting diodes (QLEDs) lags behind those of spin-coated counterparts severely. Indeed, the pursuit of high-performance inkjet-printed QLEDs is fundamentally challenging. Herein, a binary QDs ink based on cyclohexylbenzene (CHB) and indane was developed with red CdZnSe/ZnS core/shell structure without using any other additives for inkjet printing. Three common hole transport materials (HTMs), poly (9-vinlycarbazole) (PVK), poly[(9,9'-dioctylfluorenyl-2,7- diyl)-co-(4,4'-(N-(4-sec-butyl))diphenylamine)] (TFB) and poly (N, N′-bis (4-butylphenyl-N, N′-bis (phenyl) benzidine) (Poly-TPD), were invoked as the underlying layer to print QDs emissive layer, and their surface wettability and solvent resistance were systematically investigated. Among them, PVK exhibited excellent surface wettability and solvent resistance, accordingly, the PVK-based printed red QLEDs exhibited the current efficiency of 28.8 cd A−1 and the maximum external quantum efficiency (EQE) over 17.0%, which was comparable to the spin-coated QLEDs (19.8%). These results demonstrate the fabrication of efficient inkjet-printed QLED devices, which will be meaningful for printed QLEDs displays. Image 1 • 17.0% external quantum efficiency in red QLEDs was achieved by pursuing the ideal inkjet-printed film and interface. • Red quantum dot light-emitting devices (QLEDs) are fabricated by inkjet printing with more optimized QDs ink system. • The key factor of layer erosion influences the performance of inkjet-printed QLEDs. • These impressive results pave the way for future applications in printed QLEDs displays. [ABSTRACT FROM AUTHOR]

As a newly developed fluorescent material, carbon dots (CDs) have exhibited promising potentials in bioimaging and light-emitting diodes (LEDs); however, the luminescence origins are still ambiguous. Herein, we propose the surface states associated with carboxyl and carbonyl functional groups for radiative transitions in the green waveband originating from CDs according to comprehensive analyses on the spectra, interior and surface structures, and the correlations between them. The ESR signals under the dark and light conditions indicate the more contribution of carboxyl groups, and the emission change after reduction or oxidation also confirms our conclusions. A schematic of the luminescence mechanism is drawn, and the excitation-dependent behavior is recommended to be attributed to the respective dominating or the so-called competition of different transition modes under different excitations. Finally, a luminescent elastomer is prepared with the high endurance of stretch and twist. In addition, TiO2 nanowire arrays decorated with CDs exhibit an enhanced photocurrent response to visible light, indicating potential applications in photovoltaic conversion devices. [ABSTRACT FROM AUTHOR]

• This rapid post-treatment can enhance device performance in several seconds. • The device performance of the QLEDs was enhanced after IPL sintering. • After IPL sintering, the QLEDs could achieve higher efficiency at lower luminance. In this work, a rapid and innovative strategy, intense pulsed light (IPL) sintering process was incorporated to enhance the as-formed devices efficiency. After the IPL sintering on the cathode side, the maximum current efficiency was enhanced from 43.9 to 50.5 cd/A. And the EQE showed a 2.7- and a 1.9-fold improvement at 100 cd/m2 and 1000 cd/m2, respectively. The improved performance of QLED with the IPL sistering benefited from the balance between electrons and holes from the existence of insulation AlO X at the Al/ZnMgO interface. [ABSTRACT FROM AUTHOR]

Understanding the subtle structure–property relationships of quantum dots (QDs) is essential for targeted modulation of optoelectronic properties, and the influences of surface defects of inorganic halide perovskite (HP) QDs are still not very clear. Here, the negative exciton trapping effects of surface halide vacancies (VX) on the photoluminescence quantum yield QY (PLQY) of HPQDs are determined by a detailed analysis of the optical parameters, exciton dynamics, and surface chemical states. Based on the fact that VX contribute greatly to nonradiative recombination processes, versatile in situ and postpassivation strategies are developed by constructing intact Pb–X octahedrons. High QYs for standard red CsPbBr1I2 (85%), green CsPbBr3 (96%), and blue CsPbBr1.3Cl1.7 (92%) emissions are achieved. The superiorities of the reduced VX are further demonstrated by high external quantum efficiency of 0.8% and a stable emission wavelength of the blue light‐emitting diodes. This study deepens the understanding of HPQDs and demonstrates the potential for the artificial control of the optical properties of HPQDs. [ABSTRACT FROM AUTHOR]

A hydrogen-bonded amine-group doping strategy is proposed for effectively suppressing color-shift of blue PeLEDs. The theoretical and experimental results demonstrated that the N−H⋯X interaction between −NH 2 dopants and Pb−X lattices can increase the potential barriers of halide ion migration and hence stabilize the emitting wavelength even at high voltage loads, making the strategy attractive for developing color-stable perovskite optoelectronic devices for lighting and display applications. [Display omitted] Voltage loading-induced change in the electroluminescence (EL) wavelength of mixed halide perovskite light-emitting diodes (PeLEDs), so-called color-shift, has become an inevitable phenomenon, which is seriously unfavorable to their applications in lighting and display. Here, we achieve color-stable blue PeLEDs via a hydrogen-bonded amine-group doping strategy. Selecting guanidine (GA) or formamidinium (FA) as amine-group (−NH 2) doping source for CsPbBr x Cl 3− x quantum dots (QDs), experimental and theoretical results reveal that the strong N−H⋯X (X = Br/Cl) bonding can be produced between −NH 2 dopants and Pb−X lattices, thereby increasing the migration barrier of halide anions. Resultantly, color-stable sky-blue devices were realized with emission peaks fixed at 490.5 (GA) and 492.5 (FA) nm without any obvious shift as the voltage increases, in sharp contrast devices without N−H⋯X producing a 15 nm red-shift from 487 to 502 nm. Not only that, maximum external quantum efficiency is improved to 3.02% and 4.14% from the initial 1.3%. This finding offers a convenient boulevard to achieve color-stable PeLEDs with high efficiency. [ABSTRACT FROM AUTHOR]

A bidentate oxalate ion ligand-passivated strategy was proposed to improve water-resistance stability and electrical properties of CsPb(Br/Cl) 3 QDs, Profiting from the strong bonding features of oxalate ion, the QD-based light emitting diodes (QLEDs) exhibits a 5 fold enhancement in EQE, and 7-fold enhancement in stability after passivation compared to pristine QLED. This passivated strategy would provide a new idea for realizing high-performance QLEDs and QD-based optoelectronic devices. [Display omitted] • A ligand strategy for improving the waterproofing of CsPb(Br/Cl) 3 QDs was proposed. • The obtained CsPb(Br/Cl) 3 QDs can be used in electroluminescent QLED. • The efficiency and stability of fabricated QLED are simultaneously improved. Mixed halide CsPb(Br/Cl) 3 quantum dots (QDs) exhibit fine tunable blue light and narrow photoluminescence (PL) full-width at half-maximum (FWHM), which has attracted significant attention as a promising candidate to realize a new generation of blue light technology. However, the introduction of Cl− makes it very easy to be eroded by water in the environment, which will lead to deep-level defects and degrade the luminescence and stability of QDs. Here, we propose to introduce tetra- n -octylammonium oxalate (TOAOxa) to improve the water-resistance stability and exciton recombination of CsPb(Br/Cl) 3 QDs and QD-based light-emitting diodes (QLEDs). The oxalate ion (Oxa2−) of TOAOxa could form strong interaction with undercoordinated Pb2+ on CsPb(Br/Cl) 3 QD surface, which was confirmed by FTIR and XPS analysis. Oxa2− passivated QDs (Oxa-QDs) exhibited improved photoluminescence quantum yield (PLQY) and enhanced water-resistance stability compared to pristine QDs. For example, after soaking in water–acetone co-solvent for 1 h, Oxa-QDs can maintain the initial cubic morphology and 43.9% of initial PL intensity, while the morphology and luminescence of pristine QDs are almost damaged. Based on the above concept, the Oxa-QD-based QLED presented a maximum external quantum efficiency (EQE) of 4.0%, and operational lifetime (T 50) of 84 s, which was a 5-fold enhancement in EQE, and 7-fold enhancement in stability compared to pristine QLED, respectively. Besides, the Oxa-QD-based QLED exhibits better stability in high-humidity air. To sum up, the Oxa2− passivation strategy has significantly improved the efficiency and water-resistant stability of QDs and devices and would rapidly promote the development of blue-emitting QDs. [ABSTRACT FROM AUTHOR]

• The reaction yield of DBSA-QDs is 68 %, which is close to the theoretical limit. • The DBSA capped PQDs exhibit suppressed growth under various conditions. • An ion migration suppression mechanism was proposed. • The blue DBSA-QDs exhibit a steady spectrum under UV light and bias. Surface ligands play important roles in synthesis, surface passivation, colloidal stability, and modulation of optoelectronic properties for quantum dots (QDs). It is well known that conventional ligands exhibit weak binding on the surface of perovskite QDs (PQDs), resulting in uncontrolled growth and unsatisfied stability during purification and operation. This impedes the device performance progress and practical applications severely. Stronger ligands anchoring on PQDs tightly and passivating surface defects efficiently have been reported to solve the problems. Herein, we choose a representative strong ligand, dodecylbenzene sulfonic acid (DBSA), to investigate its influence on PQD growth, stability under high-temperature with various solvents and additives, and the possibility of core–shell structure construction. Interestingly, the DBSA capped PQDs exhibit abnormally ripening under above conditions. Besides, a new mechanism for ion migration suppression is proposed based on internal lattice relaxation and inter-particle migration pathway elimination. Although DBSA-PQDs can be purified several times and maintain a high quantum yield, the corresponding light-emitting diodes show poor external quantum efficiency, which might be assigned to the unbalanced colloidal stability and film conductivity. This work indicates that strong ligands provide wider space for PQD modulation and the balance between stability and device performance should also be considered. [ABSTRACT FROM AUTHOR]