High Quantum Efficiency Research Articles

Effect of band structure on the photocatalytic performance of CsPbBr3/UiO-66 composites

Photocatalytic technology driven by sunlight is rapidly developing in response to energy shortage and environmental pollution. ABX3 perovskite materials have gained widespread attention in photocatalysis due to their narrow band gap, high quantum efficiency, and high carrier mobility. The energy band structure plays a critical role in carrier generation, separation and redox processes in photocatalytic reactions. In this paper, we modulated the energy band structures of CsPbBr3 and UiO-66 by changing the reaction parameters, and prepared CsPbBr3/UiO-66 composites with different energy band structures to investigate photocatalytic activities. Our results showed that the degradation rate of (Methyl Orange) MO by CsPbBr3/UiO-66 was significantly enhanced. The change in the CsPbBr3 energy band structure did not significantly affect the photocatalytic activity of the composites. This work provides a new opportunity to improve the photocatalytic performance of perovskite-based composites using the energy band structure regulation strategy. Our findings may contribute to the design and development of highly efficient and stable perovskite-based photocatalysts for environmental remediation and energy conversion.

Graphene Intermediate Layer for Robust and Spectrum-Extended Cu Photocathode Activated with Cs and O.

Developing an effective method to stably enhance the quantum efficiency (QE) and extend the photoemission threshold of Cu photocathodes beyond the ultraviolet region could benefit the photoinjector for ultrafast electron source applications. The implementation of a 2D material protective layer is considered a promising approach to extending the operating lifetime of photocathodes. We propose that graphene can serve as an intermediate layer at the interface between photocathode material and low-work-function coating. The role of oxygen in the Cs/O activation process on the Cu surface is altered by the graphene interlayer. Besides, the few-layer graphene (FLG) surface could be more likely to induce the formation of Cs2O. Thus, the graphene-Cu composite photocathode can achieve an ultralow surface work function of down to 0.878 eV through Cs/O activation. The photoemission performance of the composite cathode with a FLG interlayer is significantly enhanced. The photocathode has an extended spectral response to the near-infrared region and a higher QE. At 350 nm, its QE is more than twice that of the cesiated bare Cu, reaching 0.247%. After degradation, the graphene-Cu cathode can be fully restored by reactivation, with remarkably enhanced stability. In addition, the composite cathode can be operated reliably under a poor vacuum pressure of over 4 × 10-6 Pa. This study validates a new method for incorporating 2D materials into photocathodes, offering novel approaches to explore robust and spectrum-extended photocathodes.

Engineering of g-C3N4 for Photocatalytic Hydrogen Production: A Review.

Graphitic carbon nitride (g-C3N4)-based photocatalysts have garnered significant interest as a promising photocatalyst for hydrogen generation under visible light, to address energy and environmental challenges owing to their favorable electronic structure, affordability, and stability. In spite of that, issues such as high charge carrier recombination rates and low quantum efficiency impede its broader application. To overcome these limitations, structural and morphological modification of the g-C3N4-based photocatalysts is a novel frontline to improve the photocatalytic performance. Therefore, we briefly summarize the current preparation methods of g-C3N4. Importantly, this review highlights recent advancements in crafting high-performance g-C3N4-based photocatalysts, focusing on strategies like elemental doping, nanostructure design, bandgap engineering, and heterostructure construction. Notably, sophisticated doping techniques have propelled hydrogen production rates to a 104-fold increase. Ingenious nanostructure designs have expanded the surface area by a factor of 26, concurrently extending the fluorescence lifetime of charge carriers by 50%. Moreover, the strategic assembly of heterojunctions has not only elevated charge carrier separation efficiency but also preserved formidable redox properties, culminating in a dramatic hundredfold surge in hydrogen generation performance. This work provides a reliable and brief overview of the controlled modification engineering of g-C3N4-based photocatalyst systems, paving the way for more efficient hydrogen production.

Isomer engineering of triptycene-fused multi-resonance TADF emitters: Implications for controlling blue electroluminescence performance

Concurrently achieving high efficiency, narrowband emission, and low efficiency roll-off remains a challenging task for realizing stable blue organic light-emitting diodes (OLEDs) with high color purity. To tackle this issue, herein, two isomeric pairs of B,N-doped multi-resonance thermally activated delayed fluorescence (MR-TADF) emitters, namely, 2,3-Tp-BuDABNA-R and 3,4-Tp-BuDABNA-R (R=H, 3,5-Xyl), featuring triptycene (Tp) moieties fused into the 2,3- and 3,4-positions of the B,N core, respectively, are presented. Both isomeric forms exhibit blue emissions with near-unity photoluminescence (PL) quantum yields in their doped host films. Notably, the 3,4-Tp-fused emitter shows 6-fold faster reverse intersystem crossing (RISC) compared to the 2,3-Tp-fused emitter, albeit with PL spectral broadening. Along with a smaller activation energy of RISC, the stronger spin–orbit coupling between the singlet (S1) and triplet (T2) excited states of the 3,4-Tp-fused emitter is suggested to facilitate the RISC process. Furthermore, a high-frequency vibration in the Tp-fused benzene ring, accompanied by a large reorganization energy, is found to mainly contribute to the spectral broadening of the 3,4-Tp-fused emitter. Blue TADF-OLEDs based on each isomeric emitter similarly achieve a high maximum external quantum efficiency of ∼ 26%. Remarkably, the devices with the 3,4-isomer exhibit significantly reduced efficiency roll-offs compared to the 2,3-isomer, demonstrating that isomer engineering of MR emitters can have a distinct impact on controlling device performance.

Design and optimization of (FA)2BiCuI6-based double perovskite solar cells using kesterite CBTS as hole transport layer for high power conversion and quantum efficiency

This work introduces the design of a novel architecture for double perovskite solar cells (DPSCs) utilizing (FA)2BiCuI6, known for its enhanced stability relative to single perovskite materials for production of efficient, ultra-thin solar cells. The proposed architecture features a unique device configuration of ITO/WO3/(FA)2BiCuI6/Cu2BaSnS4/W, incorporating a Kesterite type Cu-based quaternary chalcogenide material, Cu2BaSnS4 known as CBTS, is used as hole transport layer (HTL) with a bandgap of 1.9 eV, WO3 as the electron transport layer (ETL) with a 2.6 eV bandgap, and (FA)2BiCuI6 as the absorber layer with a 1.55 eV bandgap. The study provides an in-depth theoretical analysis of the energy band structure, defects, and quantum efficiency of the DPSC, highlighting the device’s post-optimization photovoltaic parameters. Remarkably, the optimized DPSC demonstrated superior performance with a PCE of 24.63%, Voc of 1.16 V, Jsc of 25.67 mA cm−2, and FF of 82.87%. The research also explores the effects of various factors on photovoltaic performance, including temperature, interface defect, and generation and recombination rates, as well as work function of back contact materials. The results underscore the exceptional potential of (FA)2BiCuI6, especially when combined with the HTL CBTS, in significantly reducing sheet resistance and enhancing the overall performance of solar cells. The design is validated using the SCAPS-1D simulation software tool.

Design and synthesis of efficient red space-confined thermally activated delayed fluorescence emitter

A novel red thermally activated delayed fluorescence (TADF) emitter, 2-(4,4″-bis(diphenylamino)-[1,1':3′,1″-terphenyl]-4′-yl) quinoxaline-6,7-dicarbonitrile (QCN-2TPA), was developed by incorporating two trianiline units into the ortho- and para-positions of the quinoxalin-6,7-dinitrile core. The adjacent trianiline unit and quinoxalin-6,7-dinitrile core interact spatially for through-space charge transfer, while the quinoxalin-6,7-dinitrile core and the para-positioned trianiline unit enable through-bond charge transfer. QCN-2TPA demonstrated high photoluminescence quantum efficiency and a small ΔEST. Organic light-emitting diodes using QCN-2TPA as the emitter achieved a maximum external quantum efficiency of 21.4 % with red emission peaking at 596 nm.

Synthesis of uniform sized ZnS quantum dots using hydrodynamic cavitation and their characterization

As representative non-toxic cadmium-free quantum dots (QDs), ZnS QDs with high quantum efficiency, super stability and excellent biocompatibility had attracted wide attention in the fields of photocatalysis, solar cells and biomedicine. In this study, hydrodynamic cavitation (HC) technology was applied to the preparation of ZnS QDs. By adjusting HC device parameters, water soluble ZnS QDs with small particle size, narrow particle size distribution range, high absorbance, high luminous efficiency and high quantum yield were prepared. The morphology, size distribution, element composition and optical properties of ZnS QDs were studied by various characterization methods. ZnS QDs with average particle size of 1.48 nm, fluorescence quantum yield of 34.07% and Stokes shift of 112 nm were obtained. In addition, the mechanism of preparation of ZnS QDs by using HC method was also studied. It is hoped that this HC technology can provide a new idea for large-scale preparation of ZnS QDs with excellent properties.

(Invited) Silicon Nanocrystals and Electrum Nanoclusters with High Quantum Yield for Light Converting Applications

While QDs are typically made of semiconductors, metals at low dimensions also turn to discrete electronic structure. The characteristic transition size from bulk to nanodot is lower, because Fermi level position is at the band middle, while discretization of levels starts from the band edge. Therefore, only for sizes of a metal entity ~ 1 nm a QD-like behavior manifests.Here we show that metal nanoclusters Au16Ag7 of an electrum alloy (gold-silver) with adamantanethiolate ligands possess PL quantum yield of ~ 70% in a thiol-ene polymer matrix [1]. PL is in NIR range with a large Stokes shift. Due to parity-forbidden transition the PL lifetime is in microseconds. These characteristics are similar to silicon QDs, where optical transition is also partly forbidden. Luminescence from Si QDs (5-10 nm size) may also feature high quantum efficiency when a defect-free core with good surface passivation is prepared. We have demonstrated a new synthesis method, which can reduce precursor cost by an order of magnitude from the established HSQ-based technique [2]. Si QDs prepared in this way have near-unity internal and > 50% external (quantum yield) efficiency with a large Stokes shift. In both nanomaterials the re-absorption is suppressed, which is of value for several applications.One such application is a semi-transparent photovoltaics for glazing in building-integration. It is based on a luminescent solar concentrator concept, where high efficiency and a large Stokes shift are necessary requirements for nanophosphors. In this configuration absorbed solar light is re-emitted and a large fraction of it is guided by total internal reflection to the edges for collection by standard solar cells. As a proof-of-concept we fabricated 20x20 cm2 prototypes, where Si QD-doped polymer layer is sandwiched between glass plates in a triplex geometry. Such “solar windows” feature high transparency (>80%), low haze (<3%), high color rendering index (~ 88) and, at the same time, deliver up to 0.6 W of electrical peak power under one sun [3]. Original measurement techniques were developed to characterize large-area devices [4,5].

(Keynote) Light Driven H2 Generation in Pt-Tipped CdS Nanorods: Dependence on the Pt Size and CdS Rod Length

Colloidal quantum confined semiconductor-metal nano-heterostructures are a promising class of photocatalysts for solar energy conversion. In these photocatalysts, the semiconductor domain serves as the light absorber and the metal as the catalyst. Such photocatalysts combine the superior light absorption and charge transport properties of the semiconductor with the superior catalytic activity and selectivity of the metal. Furthermore, both domains can be independently tuned to enhance the photocatalytic performance of the heterostructure. Among various semiconductor/metal heterostructures, metal-tipped colloidal semiconductor nanorods have attracted extensive interest because they have been reported to have high quantum efficiencies of light driven H2 generation and their morphology can be systematically tuned. The overall light driven H2 generation process involves multiple elementary charge separation and recombination steps in the semiconductor and across the semiconductor/metal interface as well as proton-coupled electron transfer reactions at the catalytic center. The change of the semiconductor or metal domains can often have effects on multiple competing processes involved in the overall reaction. As a result of these complexities, the mechanisms for the morphological dependence of the observed H2 generation efficiencies are not fully understood, hindering the rational design of these photocatalysts. In this talk, we use Pt tipped CdS nanorods (CdS-Pt) as a model system to examine the effect of Pt size and CdS rod length on their light driven H2 generation efficiency. We show that increasing the Pt particle size increases the overall H2 generation quantum efficiency through both increasing the rate of electron transfer from the CdS to Pt and enhancing the efficiency of water/proton reduction; H2 generation efficiency increases at longer CdS rod length by suppression of charge recombination across the Pt/CdS interface. Furthermore, because of rapid trapping of valence band holes, multi-exciton states in CdS nanorods can be long lived, enabling efficient multi-electron transfer to the Pt. Our work demonstrates that through systematic in situ study of elementary processes involved in the overall H2 generation, it is possible to rationally design and improve semiconductor-metal hybrid photocatalysts.

Efficient Deep-Blue Light-Emitting Diodes Through Decoupling of Colloidal Perovskite Quantum Dots.

Metal halide perovskite light-emitting diodes (PeLEDs) have exceptional color purity but designs that emit deep-blue color with high efficiency have not been fully achieved and become more difficult in the thin film of confined perovskite colloidal quantum dots (PeQDs) due to particle interaction. Here it is demonstrated that electronic coupling and energy transfer in PeQDs induce redshift in the emission by PeQD film, and consequently hinder deep-blue emission. To achieve deep-blue emission by avoiding electronic coupling and energy transfer, a QD-in-organic solid solution is introduced to physically separate the QDs in the film. This physical separation of QDs reduces the interaction between them yielding a blueshift of ≈7nm in the emission spectrum. Moreover, using a hole-transporting organic molecule with a deep-lying highest occupied molecular orbital (≈6.0eV) as the organic matrix, the formation of exciplex emission is suppressed. As a result, an unprecedently high maximum external quantum efficiency of 6.2% at 462nm from QD-in-organic solid solution film in PeLEDs is achieved, which satisfies the deep-blue color coordinates of CIEy <0.06. This work suggests an important material strategy to deepen blue emission without reducing the particle size to <≈4nm.

Reverse Intersystem Crossing Boosting Sensitizer for Ultra-High Efficiency Blue Organic Light-Emitting Diode.

In designing thermally activated delayed fluorescence (TADF) emitters, a high reverse intersystem crossing (RISC) rate with a high photoluminescence quantum yield is essential. Herein, two blue TADF molecules, 2',5'-di(9H-carbazol-9-yl)-3',6'-bis(3,6-ditert-butyl-9H-carbazol-9-yl)-[1,1':4',1″-terphenyl]-4,4″-dicarbonitrile (CzTCzPhBN) and 2',5'-bis(3,6-ditert-butyl-9H-carbazol-9-yl)-3',6'-bis(3,6-diphenyl-9H-carbazol-9-yl)-[1,1':4',1″-terphenyl]-4,4″-dicarbonitrile (PhCzTCzPhBN) with a high RISC rate, were developed through donor engineering. CzTCzPhBN and PhCzTCzPhBN showed a high RISC rate of 4.00 × 105 and 16.62 × 105 s-1, respectively, with a high photoluminescence quantum yield of 80.1 and 84.9%, which resulted in high external quantum efficiency of 27.0 and 27.8% with color coordinates (0.148, 0.170) and (0.150, 0.230) in blue TADF organic light-emitting diodes, respectively. The high RISC rate and device efficiency inspired two TADF molecules to be used as sensitizers in hyperfluorescence devices. The hyperfluorescence devices showed ultra-high external quantum efficiency of 30.7 and 36.4% with color coordinates (0.125, 0.164) and (0.127, 0.193), respectively.

Regulating the Oxygen Vacancy on Bi2MoO6/Co3O4 Core‐Shell Nanocage Enables Highly Selective CO2 Photoreduction to CH4

AbstractPhotocatalytic CO2 reduction reaction (CO2RR) into high‐value‐added fuels has received significant attention, yet multiple electron and proton processes involved in CO2RR result in low selectivity. Herein, a strategy involving oxygen vacancies (Ovs)‐enriched Bi2MoO6 coated on ZIF‐67‐derived Co3O4 to construct well‐defined core‐shell nanocage is developed, which drives effective CO2 photoconversion to CH4 with nearly 100% selectivity and high apparent quantum efficiency of 2.5% at 420 nm in pure water under simulated irradiation. Theoretical calculations and experiments exhibit that the potential difference stemming from the built‐in electric field provides guarantee for CO2 reduction occurring on Bi2MoO6 and H2O oxidation set in Co3O4. Numerous exposed Bi2MoO6 with Ovs formed in Bi─O bond by ethylene glycol mediated approach promotes the CO2 adsorption and charge separation efficiency, which can optimize the reaction kinetics and thermodynamics, facilitating the hydrogenation of key intermediate *CO to generate CH4. This work provides a new strategy for controlled oxygen vacancy generation on photocatalysts to achieve high‐performance CO2 methanation.

Leveraging the dynamics of microalgal CO2 capture to estimate the maximum inherent photosynthetic potential

AbstractBACKGROUNDNatural photosynthesis, utilizing intelligent molecular machinery to harness sunlight, stands as the benchmark for efficient energy generation. Despite its high quantum efficiency compared to synthetic methods, challenges persist due to dynamic nutritional and light requirements in plant, microalgae, and cyanobacteria‐driven processes. Reported microalgae CO2 uptake rates rely on biomass dry cell weight measurement after certain incubation period and systematic study of required CO2 concentrations for optimal photobioreactor operation remaining unexplored. This research is thus aimed at evaluating the critical dissolved CO2 (Ccrit ∙ CO2) concentration and specific CO2 uptake rates (SCUR) of Chlorella minutissima (CM) culture in the presence of surplus light and other nutrients by online monitoring and measuring the dynamic CO2 uptake rates which will help in maintaining the optimal rate of CO2 delivery for continuous cultivation of microalgae while minimizing the escape of CO2.RESULTSDissolved Ccrit ∙ CO2 was determined to be in the range of 16–20 mg/L, and the maximum SCUR in BBM (Bold Basal Medium) was found to be 0.73 mg CO2 (mg dcw ∙ h)−1. Interestingly, this SCUR value is nearly three times greater than that of the most efficient in vitro artificial photosynthetic novel pathway reported so far.CONCLUSIONFrom the calculated SCUR values, it may be noted that 9.6 g of biomass can be obtained from 1 g of microalgal inoculum in a day, thereby setting a benchmark for the scientists working in the areas of bioprocess engineering, synthetic biology, and metabolic engineering to comply. © 2024 Society of Chemical Industry (SCI).

A novel fluoroapatite-type phosphor Ca2Y8(BO4)2(SiO4)4F2:Eu3+ with high quantum efficiency and good thermal stability for multimodal applications☆

A novel Eu3+ doped fluorapatite red phosphor Ca2Y8(BO4)2(SiO4)4F2:Eu3+ with pure phase was synthesized in this study. Density functional theory (DFT) calculation and diffuse reflection spectrum analysis reveal its potential as a matrix for phosphors excited by ultraviolet light. Eu3+ has a 7F0→5L6 transition at 394 nm, and the prepared phosphor exhibits a high emission intensity at 614 nm, which may be attributed to the 5D0-7F2 energy transition at the lower symmetry site of Eu3+. The optimal doping concentration of the phosphor is determined to be 11 mol%, with concentration quenching attributed to the exchange interaction mechanism. The overall color purity of the phosphor is up to 99.88%, with an internal quantum efficiency as high as 91.15%. Notably, Ca2Y8(BO4)2(SiO4)4F2:11 mol%Eu3+ (CYBSF:11 mol%Eu3+) phosphors exhibit good thermal stability, with a thermal quenching temperature (T1/2) of 552 K and the intensity of emission at 423 K still at 88.89% of that at 298 K. The activation energy of the phosphor is up to 0.30287 eV. Its comprehensive luminescence performance surpasses that of commercial red phosphor, making it suitable for near ultraviolet excited warm white light emitting diode (NUV-WLED) with a high color rendering index (Ra = 82) and a correlation color temperature (CCT) of 4339 K. Moreover, the phosphor achieves latent fingerprint visualization and anti-counterfeiting ink on different material surfaces: glass, aluminum foil, plastic and paper. Overall, the fluorapatite CYBSF:11 mol%Eu3+ phosphor holds great potential for multimodal applications due to its high quantum efficiency and good thermal stability.

Garnet-type cyan-green-emitting SrLu2Ga1.5Al2.5SiO12:Ce3+ phosphor with high quantum efficiency, thermal stability, and water resistance for blue-excited WLEDs

Nowadays, high-quality phosphor-converted white light-emitting diodes (pc-WLEDs) ought to include cyan-emitting phosphors allowing for full-spectrum light similar to sunlight. Herein, we report a garnet-structured Ce3+-doped SrLu2Ga1.5Al2.5SiO12 (SLGASO) phosphor that significantly compensates for the absence of cyan light, known as the “cyan cavity”. The SLGASO host crystallizes into a cubic structure with the space group. The cell parameters were determined using Rietveld refinement. Under 430 nm blue excitation, SLGASO:Ce3+ emits intense cyan-green light in the 450‒700 nm wavelength range. The representative SLGASO:0.07Ce3+ phosphor has an internal quantum efficiency (IQE) of 95.4% and excellent thermal stability, remaining 92.7% of its initial emission intensity at 152 °C. After 155 d of immersion in water, the luminous intensity of SLGASO:0.07Ce3+ remains constant, confirming its waterproofness. Furthermore, a pc-WLED device with luminous efficiency (LE) of 101.58 lm/W, color rendering index (Ra) of 91, correlated color temperature (CCT) of 4536 K, and Commission Internationale de L’Eclairage (CIE) chromaticity coordinates of (0.3555, 0.3390) was fabricated by combining as-prepared cyan-green-emitting SLGASO:0.07Ce3+, yellow-emitting Y3Al5O12:Ce3+ (YAG:Ce3+), and red-emitting (Ca,Sr)AlSiN3:Eu2+ phosphors, as well as a 450 nm blue chip. These findings indicate that SLGASO:0.07Ce3+ phosphor can bridge the cyan gap and improve the performance of as-fabricated full-visible-spectrum WLEDs.

Rational Design of Fluorophores Using MO Theory: Our Journey from BODIPYs to BOIMPYs

This short review demonstrates how MO-theoretical considerations can support the tailor-made design of new dye scaffolds, specifically the recently introduced BOIMPY class of fluorophores. Starting with historical and structural foundations, the influence of canonical streptocyanines on the electronic features of diarylmethenes and rhodamines is examined and the BODIPY scaffold is introduced as the primary structural inspiration for our work. The attachment of five-membered ring heterocycles at the meso position of the BODIPY core enables a relaxation into a co-planar and twofold chelating triarylmethene system. After introduction of two electron-withdrawing BF2 units, efficient rigidity is achieved since hindered rotation prevents non-radiative dissipation of energy via excited state relaxation. Hence, a lowered LUMO level allows the combination of a large red shift with high quantum efficiencies. The synthetic approach to BOIMPYs is straightforward and analogous to BODIPY syntheses starting from benzimidazole or tetrazole carbaldehydes. Cyclic voltammetric measurements prove that BOIMPYs are able to easily accept two electrons and might act as efficient photoredox catalysts.

A novel high-efficient NIR emitting phosphor Ca2YAl3Ge2O12:Cr3+ enabled by chemical unit co-substitution

Near-infrared phosphor-converted light-emitting diodes (NIR pc-LEDs) demonstrate a great prospect for applications in the field of bioimaging, modern agriculture, and nondestructive examination. Developing NIR emitting phosphor with high quantum efficiency (QE) and thermal stability is a significant issue. Herein, a novel highly efficient NIR-emitting phosphor Ca2YAl2.95Ge2O12:0.05Cr3+ is reported. Through chemical unit co-substitution of [Ca2+ + Ge4+] by [Al3+ + Y3+] in Ca3Al1.95Ge3O12:0.05Cr3+, when one-third of the Ca2+/Ge4+ sites were replaced by Y3+/Al3+, the internal and external QEs are 84.1 % and 38.6 %, respectively. Its emission peak was red-shifted to 780 nm compared with that of Ca3Al1.95Ge3O12:0.05Cr3+, which is in favor of matching with the absorption band of phytochrome PFR (600–800 nm). The Ca2YAl2.95Ge2O12:0.05Cr3+ phosphor shows high heat stability and its photoluminescence (PL) intensity at 423 K remains 80.38 % of that at 300 K. The photoelectronic conversion efficiency of the NIR pc-LED device fabricated by Ca2YAl2.95Ge2O12:0.05Cr3+ phosphor and 450 nm blue chip can reach 15.88 % at 180.5 mA drive current. All the results indicate that Ca2YAl2.95Ge2O12:0.05Cr3+ phosphor has excellent application potential in night vision and plant lighting.

Stable and efficient all-inorganic quantum dot light-emitting diodes based on a double-layer electron transport layer

Abstract The most advanced quantum light-emitting diodes (QLEDs) have achieved almost unity external quantum efficiency (EQE) due to organic materials for high transport efficiency, but organic materials are less stable and can lead to irreversible degradation of the devices. The use of stable inorganic hole-transporting layers (HTLs), such as NiOx, becomes a promising alternative. ZnO is a common electron-transporting material in QLEDs, which possesses high mobility and tunable conductivity properties, but ZnO-based QLEDs devices undergo loss of efficiency due to exciton bursting, poor shelf stability, and pronounced positive aging effects. SnO2, as a common electron-transporting material, has better stability than ZnO. In this work, the SnO2/ZnO dual electron transport layer strategy is adopted, which can reduce the non-radiative burst and aging behavior, and at the same time, the electron transport is regulated by adjusting the film thickness. Inorganic QLEDs with high external quantum efficiency (9.5%) as well as high operational stability have been fully realized. This strategy provides effective ideas for future high-performance display devices.

Near-Complete Suppression of NIR-II Luminescence Quenching in Halide Double Perovskites for Surface Functionalization Through Facet Engineering.

Lanthanide-based NIR-II-emitting materials (1000-1700nm) show promise for optoelectronic devices, phototherapy, and bioimaging. However, one major bottleneck to prevent their widespread use lies in low quantum efficiencies, which are significantly constrained by various quenching effects. Here, a highly oriented (222) facet is achieved via facet engineering for Cs2NaErCl6 double perovskites, enabling near-complete suppression of NIR-II luminescence quenching. The optimally (222)-oriented Cs2Ag0.10Na0.90ErCl6 microcrystals emit Er3+ 1540nm light with unprecedented high quantum efficiencies of 90±6% under 379nm UV excitation (ultralarge Stokes shift >1000nm), and a record near-unity quantum yield of 98.6% is also obtained for (222)-based Cs2NaYb0.40Er0.60Cl6 microcrystallites under 980nm excitation. With combined experimental and theoretical studies, the underlying mechanism of facet-dependent Er3+ 1540nm emissions is revealed, which can contribute to surface asymmetry-induced breakdown of parity-forbidden transition and suppression of undesired non-radiative processes. Further, the role of surface quenching is reexamined by molecular dynamics based on two facets, highlighting the drastic two-phonon coupling effect of a hydroxyl group to 4I13/2 level of Er3+. Surface-functionalized facets will provide new insights for tunable luminescence in double perovskites, and open up a new avenue for developing highly efficient NIR-II emitters toward broad applications.

Synthesis of layered scheelite SrLa2(MoO4)4: Eu3+ red phosphors with high quenching concentration and superior quantum efficiency for improving plant photosynthesis

Plant growth light-emitting diodes (LEDs) are gaining more interest in indoor agriculture because they can provide light spectra that better suit the growth needs of crops. Nevertheless, the big challenge of developing red phosphors that exhibit both exceptional thermal stability and high quantum efficiency remains a daunting undertaking. In this work, Eu3+ activated SrLa2(MoO4)4 red phosphors with layered scheelite structure have been successfully developed. When excited with light of 394 nm, these novel phosphors show the strongest emission at 615 nm. Particularly, the addition of NH4Cl flux significantly increased the quantum efficiency of SrLa2(MoO4)4: Eu3+, reaching an impressive 94.5%. In addition, even at a high temperature of 150 °C, the luminescence intensity remained at a remarkable 65.3% in comparison with the room temperature (RT) emission intensity. A red LED device with a photoelectric conversion efficiency of 5.4% and an output power of 35.9 mW at a drive current of 200 mA was prepared by using this red phosphor. Plant photosynthesis study demonstrated that the lotus leaves exposed to red LED lighting for a few weeks had a larger average diameter than those exposed to natural sunlight, which shows that the SrLa2(MoO4)4: Eu3+ phosphor efficiently converts the light provided by LEDs into red light beneficial for plant growth.