Wide Full Width Research Articles

One-step solvothermal synthesis of nitrogen-doped carbon dots with efficient red emission from conjugated perylene for multiple applications

Despite its significance for applications related to plant growth, the development of carbon dots (CDs) with bright red emissions still faces multiple obstacles. Herein, red emission hydrophobic carbon dots (RH-CDs) featuring one emission peak centered at 594 nm and a shoulder emission peak at 630 nm with a quantum yield of 34 % and a wide full width at half maximum (FWHM) of 100 nm (580 nm–680 nm) were synthesized by adopting large conjugated perylene anhydride and aromatic amine precursors under solvothermal conditions. Density functional theory calculations support the method of using larger conjugated systems and higher graphite N doping to increase red emissions from CDs. With a post-surface functionalization strategy, polyvinylpyrrolidone (PVP)-modified RH-CDs (QY = 12 %) were utilized as an anti-counterfeiting ink for information printing. Moreover, both blue-red light-emitting diodes (LEDs) and light conversion poly (methyl methacrylate) (PMMA)-CDs film were fabricated with emission spectra that are consistent with the absorption spectra of plants, suggesting that the prepared RH-CDs may have widespread application potential as a stable fluorescent material in plant growth.

Morphological insights into uncompetitive fluorescence of coal-based carbon dots and strategies for improvement

The findings of the research indicate that coal-derived carbon dots (CDs), produced through top-down methods, exist as a blend of graphene quantum dots (GQDs), carbon quantum dots (CQDs), and carbon nanodots (CNDs). Within this mixture, numerous individual particles are dispersed, each containing multiple sp2-carbon domains, suggesting the presence of multiple fluorescent centers of varying sizes. These fluorescent centers scatter photon energy, leading to a wide full width at half maximum (FWHM >80 nm). To tackle this issue, the study significantly improves the fluorescence efficiency of coal-based CDs by employing a nitrogen-doping approach. Additionally, these nitrogen-doped CDs are combined with polyvinyl alcohol (PVA) to formulate secure inks exhibiting solid-state fluorescence and room-temperature phosphorescence (RTP) properties, showcasing their potential for anti-counterfeiting applications in safeguarding important documents and artworks.

P‐139: Effect of Surface Ligands on Device Performance for Infrared Light‐Emitting Diodes†

Infrared (IR) emitted Quantum Dots (QDs) are fascinating materials with the unique feature of energy levels engineering based on ligand exchange. In this work, the ligand of QDs is modified to form the charge transport layer of IR light‐emitting diodes (LEDs). The corresponding IRLEDs fabricated with all QDs materials can obtain electroluminescence (EL) peak of 1200 nm, including the wide full width at half maximum (FWHM), and an EQE of 4.5%.

Achieving broadband NIR-I to NIR-II emission in layer-structured Mg4Nb2O9:Cr3+,Yb3+ phosphor for multifunctional applications

Broadband near-infrared (NIR) phosphor-converted light-emitting diodes (pc-LEDs) have garnered unprecedented attention in photonic, optoelectronic and biological applications. Here, an efficient broadband NIR phosphor Mg4Nb2O9:Cr3+ was achieved. Excited by 455 nm blue light, the Mg4Nb2O9:Cr3+ phosphor exhibited a maximum peak at 863 nm with a relatively wide full width at half maximum (FWHM) of approximately 178 nm and the internal quantum efficiency (IQE) was measured to be 94 %. The observed broadband emission in the NIR range can be attributed to two distinct Cr3+ centers within the Mg4Nb2O9 structure, namely Mg2+ and Mg2+-Mg2+ dimer, which was confirmed through luminescence, decay kinetic analysis and density function theory (DFT) calculations. To further broaden the NIR emission, Yb3+ was co-doped with Cr3+ in Mg4Nb2O9. Benefited from the efficient energy transfer from Cr3+ to Yb3+, the codoped Mg4Nb2O9:Cr3+, Yb3+ shows a bandwidth of 223 nm and IQE of 86.4 %. The pc NIR-LED device incorporating this phosphor achieved a NIR output power of 131.6 mW at input current of 400 mA, with a photoelectric conversion efficiency of 44.2 %. Finally, the constructed NIR-LED demonstrated multifunctional applications in non-destructive detection and information encryption.

A Double Perovskite Single Crystal CsCuAgI3.

Eco-friendly halide double perovskites are attracting significant attention as potential substitutes for traditional lead-based halide perovskites. However, their typically wide or indirect band gap limits further technological advancement. This study presents a new, eco-friendly, all-inorganic millimeter-scale CsCuAgI3 single crystal (SC). The crystal exhibits a direct band gap of 2.02 eV at the G-point, markedly superior to that of traditional double perovskites. The absorption and photoluminescence spectra further corroborate its band gap attributes. Owing to the B-site Cu-Ag disorder, the crystal possesses a higher Urbach energy (119 meV), indicative of structural disorder. CsCuAgI3 exhibits a wide Stokes shift of 230 nm, a wide full width at half-maximum (fwhm) of 152 nm, a long fluorescence lifetime of 7.29 μs, and excellent stability. In addition, a photoelectric detection prototype was prepared using a CsCuAgI3 single crystal. Using a 375 nm laser as the excitation source, the device showed a very sensitive photoelectric response, clocking in at (0.37/0.21) seconds. This work offers new insights into developing novel lead-free double perovskite single crystals and exploring their potential applications.

Spatial and temporal evolution of electromagnetic pulses from solid target irradiated with multi-hundred-terawatt laser pulse inside target chamber

Giant electromagnetic pulses (EMPs) induced by high-power laser irradiating solid targets interfere with various experimental diagnoses and even damage equipment, so unveiling the evolution of EMPs inside the laser chamber is crucial for designing effective EMP shielding. In this work, the transmission characteristics of EMPs as a function of distances from the target chamber center (TCC) are studied using B-dot probes. The mean EMP amplitude generated by picosecond laser-target interaction reaches 561 kV m−1, 357 kV m−1, 395 kV m−1, and 341 kV m−1 at 0.32 m, 0.53 m, 0.76 m, and 1 m from TCC, which decreases dramatically from 0.32 m to 0.53 m. However, it shows a fluctuation from 0.53 m to 1 m. The temporal features of EMPs indicate that time-domain EMP signals near the target chamber wall have a wider full width at half maximum compared to that close to TCC, mainly due to the echo oscillation of electromagnetic waves inside the target chamber based on simulation and experimentation. The conclusions of this study will provide a new approach to mitigate strong electromagnetic pulses by decreasing the echo oscillation of electromagnetic waves inside the target chamber during laser coupling with targets.

Design of bandwidth-enhanced polarization controlled frequency selective surface based microwave absorber

Abstract A design of a microwave absorber based on frequency selective surface resonating in X-band having ultrathin thickness, polarization controlled behavior, and increased absorption bandwidth has been reported. The reported absorber having its unit cell embodied of multiple resonating structures which includes conventional square, circular, and butterfly shaped resonators resulting in three absorption apexes at 9.44, 10.00, and 10.53 GHz (all in X band) with 99.9%, 99%, and 95.1% of absorptivity obtained at the frequencies of resonances. It demonstrates a wide full width at half maximum having 1.48 GHz as bandwidth, at the expense of using an ultrathin substrate of 0.0096 λ0, where λ0 is the wavelength with respect to lowest resonating frequency, i.e. 9.44 GHz. The unit cell is fourfold symmetric exhibiting independence about the absorber’s polarity, as well as, it behaves stable over the outspread angle up to 45 degrees for both transverse magnetic and transverse electric polarized wave under sloped incident angle. The absorption behavior has been demonstrated by plotting the distribution of surface-currents and electric fields at the frequencies of resonance. The fabricated prototype of the presented design is tested at X-band and the obtained results concur with the simulated results.

Broadband near-infrared luminescence in the novel Li3Cs2Sr2B3P6O24:Cr3+ phosphor for NIR pc-LED

Broadband phosphors materials with near-infrared emission have recently gained significant attention for their applications in bio-medication and bio-imaging, phototherapy, night vision, non-destructive diagnostic solution, and quality/risk control of food. This study introduces a novel phosphor material with a broad NIR emission spanning 700–1100 nm. Under 450 nm excitation, this material features a wide full width at half maximum (FWHM) of 170 nm. This broad-spectrum emission results from Cr3+ ion occupancy at Sr2+ sites. A promising quantum yield (PLQY) of 34.7 % was measured. The emission intensity at 423 K maintains 31.3 % of that at 298 K, which needs to be improved. Moreover, successful fabrication of packaged near-infrared phosphor-converted LEDs (pc-LEDs) displaying a broad emission centered on 890 nm further underscores the exceptional potential of Li3Cs2Sr2B3P6O24:Cr3+ phosphors in the realm of broadband NIR pc-LED applications.

All-dielectric metasurface refractive index sensor with high figure of merit based on quasi-bound states in the continuum

All-Dielectric metasurfaces are widely used in the field of sense due to their small size, freedom of design, and low radiation loss. However, the optical sensor still has the problem of wide full width at half maximum (FWHM), which leads to a low figure of merit (FOM). In order to solve this problem, an all-dielectric metasurface based on quasi-bound states in the continuum (q-BIC) was proposed for refractive index sensing. The sensor structure consisted of a prism/metasurface/analyte, where the metasurface was composed of periodically arranged subwavelength asymmetric silicon gratings. The asymmetry of the structure led to the coupling of the tangential and radiative field components in the superficial layer at the resonance position, which formed a q-BIC resonance peak with a narrow FWHM in the reflection spectrum. We explained the causes of the q-BIC resonance peak generation by finite element analysis, and analyzed the factors affecting the FWHM, and also simulated the machining errors. The results showed that by reducing the asymmetry of the sensor, it could have a high FOM, with a FOM of 1.35 × 107 RIU−1. In addition, simulated machining errors within ±5 nm showed that small machining errors did not lead to the disappearance of q-BIC, which proved that the sensor had good robustness. These findings had provided ideas for the accurate detection of trace substances.

Mode-Coupling Generation Using ITO Nanodisk Arrays with Au Substrate Enabling Narrow-Band Biosensing.

Plasmonic metal nanostructures have promising applications in biosensing due to their ability to facilitate light-matter interaction. However, the damping of noble metal leads to a wide full width at half maximum (FWHM) spectrum which restricts sensing capabilities. Herein, we present a novel non-full-metal nanostructure sensor, namely indium tin oxide (ITO)-Au nanodisk arrays consisting of periodic arrays of ITO nanodisk arrays and a continuous gold substrate. A narrow-band spectral feature under normal incidence emerges in the visible region, corresponding to the mode-coupling of surface plasmon modes, which are excited by lattice resonance at metal interfaces with magnetic resonance mode. The FWHM of our proposed nanostructure is barely 14 nm, which is one fifth of that of full-metal nanodisk arrays, and effectively improves the sensing performance. Furthermore, the thickness variation of nanodisks hardly affects the sensing performance of this ITO-based nanostructure, ensuring excellent tolerance during preparation. We fabricate the sensor ship using template transfer and vacuum deposition techniques to achieve large-area and low-cost nanostructure preparation. The sensing performance is used to detect immunoglobulin G (IgG) protein molecules, promoting the widespread application of plasmonic nanostructures in label-free biomedical studies and point-of-care diagnostics. The introduction of dielectric materials effectively reduces FWHM, but sacrifices sensitivity. Therefore, utilizing structural configurations or introducing other materials to generate mode-coupling and hybridization is an effective way to provide local field enhancement and effective regulation.

P‐69: Ligand Treatment on Quantum Dots to Obtain Highly Stable Infrared Light‐Emitting Diode

Quantum dots (QDs) are chemically produced materials with a variety of interesting features that can be employed in various applications ranging from light‐emitting diodes (LEDs) to sensors. In this work, we report an infrared QDs‐based LED (IRLED), in which the QDs are treated with ligands and formed a smooth emissive layer of the device. The ligand treatment steps ensure the quality and morphology of the QDs emissive layer. During three weeks, the fabricated IRLED device achieved an equable current, steady electroluminescence (EL) peak of 1197 nm, a wide full width at half maximum (FWHM) of 226 nm, and a high EQE of 9%.

Substrate Dependence of CdSe/ZnS Quantum-Dot Light-Emitting Diodes: A Comparative Study between Rigid Glass and Flexible Plastic Substrates.

The purpose of this study was to investigate the effect of substrate characteristics on the performance of quantum-dot light-emitting diodes (QLEDs) with the aim of developing high-performance flexible QLEDs. Specifically, we compared QLEDs made with a flexible polyethylene naphthalate (PEN) substrate to those made with a rigid glass substrate, using the same materials and structure except for the substrates. Our findings indicate that the PEN QLED had a 3.3 nm wider full width at half maximum and a 6 nm redshifted spectrum in comparison to the glass QLED. Additionally, the PEN QLED exhibited a 6% higher current efficiency, a flatter current efficiency curve, and a 2.25-V lower turn-on voltage, indicating superior overall characteristics. We attribute the spectral difference to the optical properties of the PEN substrate, such as light transmittance and refractive index. Our study also revealed that the electro-optical properties of the QLEDs were consistent with the electron-only device and transient electroluminescence results, which suggests that the improved charge injection properties of the PEN QLED were responsible. Overall, our study provides valuable insights into the relationship between substrate characteristics and QLED performance, which can be used to develop high-performance QLEDs.

Sequential Vacuum Evaporated Copper Metal Halides for Scalable, Flexible, and Dynamic X‐Ray Detection

AbstractCopper metal halides have emerged as a strong contender in the scintillator field due to the self‐trapped excitons (STEs) mechanism. However, their development has been hindered by the preparation process. Single crystals have long growth cycles and cannot achieve large areas and flexibility. Quantum dots have a low yield and can easily cause chemical pollution, and the thickness of films prepared by the spin coating cannot be controlled. To address these challenges, a new method for preparing Cs3Cu2Cl5 using sequential vacuum evaporation is developed. This allows successful preparation of large‐area (≈100 cm2) and flexible films. The STEs mechanism of Cs3Cu2Cl5 gives it unique properties such as a large Stokes shift that reduces self‐absorption effects, and a wide full width at half‐maximum that improves coupling with photodiodes. Therefore, Cs3Cu2Cl5 is applied to X‐ray imaging with a light yield of ≈30 000 photons MeV−1, a spatial resolution of over 10 lp mm−1, and a low detection limit below 0.8 µGyair s−1. In addition, the flexible Cs3Cu2Cl5 film enables effective dynamic imaging and clear imaging on non‐planar objects. It also exhibits good resistance to harsh environments, maintaining good imaging performance after 150 days. It is believed that sequential vacuum evaporation provides an important idea for preparing scintillators.

Dopant and compositional modulation triggered long-wavelength ultra-broadband and tunable NIR emission in MgO: Cr3+ phosphor for NIR spectroscopy applications

Efficient ultra-broadband near-infrared (NIR) phosphors with long-wavelength ( λ max > 850 nm) and wide full width at half-maximum (FWHM, >200 nm) have sparked tremendous interest, demonstrating their immense potential in NIR spectroscopy technology. Nevertheless, the development of NIR spectroscopy technology suffers from the restricted capability to efficiently emit the ultra-broadband NIR light. Herein, the synergetic enhancement strategy of heterogeneous substitution and compositional modulation was applied to create a novel Cr 3+ doped long-wavelength ultra-broadband MgO: Cr 3+ , Ga 3+ phosphor, which exhibited a long-wavelength ultra-broadband NIR emission ( λ max = 850 nm) covering the range of 650–1300 nm on the electromagnetic spectrum with the FWHM of more than 200 nm under the excitation of 468 nm light. Furthermore, the tunable NIR emission from 818 nm to 862 nm with an optimized quantum efficiency of 30% was accomplished by the Ga 3+ ions substitution and Cr 3+ ions modulation. The phosphor exhibited remarkable thermal stability up to 100 °C, remaining 83% of the integrated emission intensity at room temperature. A prototype of the NIR phosphor-converted LED (pc-LED) demonstrated that the novel MgO: Cr 3+ , Ga 3+ phosphor possessed a relatively strong NIR output power (15.05 mW at 100 mA driven current) with a photoelectric conversion efficiency of 5.53%, which is impressive compared with other Cr 3+ -doped long-wavelength ultra-broadband phosphors. This work not only proposes a novel long-wavelength ultra-broadband NIR phosphors with industrialization and great application prospect in night vision but highlights a synergetic enhancement strategy to effectively boost the performance of long-wavelength ultra-broadband NIR pc-LED light sources.

A High-FOM surface plasmon resonance sensor based on MMF-TUMMF-MMF structure of optical fiber

The figure of merit (FOM) of conventional surface plasmon resonance (SPR) sensors is low due to the low sensitivity and wide full width at half maxima (FWHM) caused by many low-intensity high-order cladding modes. To address this problem, this paper proposes a SPR sensor based on U-shaped tapered arm cascade of multimode fiber (TUMMF). The U-shaped macro-bend increases the intensity of the light field leaking into the cladding, and the tapered area makes the number of higher-order modes smaller to achieve high sensitivity and narrow FWMH sensing performance. Through simulation and experimental verification, the sensitivity of the sensor is proportional to the fiber curvature and taper ratio, and the FWMH is inversely proportional. Therefore, the parameters of the sensor are optimized by integrating the FOM and the mechanical strength of the sensor. The optimized sensor parameters are 3 mm bending diameter, 0.85 taper ratio, and 152 nm gold film thickness. The sensor was tested in the refractive index (RI) sensing range of 1.3324–1.3731 and showed a sensitivity of 4816.092 nm/RIU and a FWMH of 97.54 nm. The FOM of the proposed sensor is 49.37 /RIU, which is 3.18 times higher than that of the U-shaped multimode fiber SPR sensor. The probe has the advantages of simple fabrication, high environmental stability and easy modification, and has a wide range of applications in bioenvironmental and other fields.

Te4+-doped Cs2InCl5·H2O single crystals for remote optical thermometry

Zero-dimensional metal halide perovskites have captured intense research interest owing to their unique optoelectronic properties. Particularly, metal halides with the ns2 electronic configuration are of great interest owing to the high-temperature sensitivity of their photoluminescence, which could be applied to remote optical thermometry (ROT). Herein, all-inorganic and lead-free halide perovskite Te4+-doped Cs2InCl5·H2O single crystals (SCs) were prepared through the hydrothermal method and showed a strong temperature dependence of photoluminescence lifetime. Upon Te4+ doping, the nonemissive Cs2InCl5·H2O SC exhibits a bright orange emission at 660 nm with a wide full width at half maximum of 180 nm. The strong phonon-exciton coupling promotes the formation of self-trapped excitons in the soft lattice of the zero-dimensional Te4+-doped Cs2InCl5·H2O SC. The Te4+ ions with the 5s2 electronic configuration endow the Te4+-doped Cs2InCl5·H2O SC with a strong temperature-dependent photoluminescence lifetime. This SC reaches a maximum specific sensitivity of 0.062K−1 at 320 K, thereby showing the potential advantages of indium-based metal halide perovskites in ROT applications.

Industrial mass production of novel mixed-halide Cs3Cu2Cl5-xIx and Cs5Cu3Cl8-xIx compounds with greatly enhanced stability and luminescent efficiency by compositional engineering

• The compositional engineering of novel mixed-halide for the first time was explored. • Mixed-halide compound shows dramatic improved stability and efficiency. • The controllable phase transformation from Cs 3 Cu 2 I 5 to CsCu 2 I 3 was discovered. • White light is obtained by combining mixed-halide compound with CsCu 2 I 3 powders. • WLED with high CRI is achieved by combining Cs 5 Cu 3 Cl 7 I MHPPs and CsCu 2 I 3 powders. Copper(I) halides have recently attracted increasing attention in a variety of photonics applications, owing to their highly luminescent efficiency, nontoxicity, and low-dimensional electronic structure. Moreover, combining compositional engineering and mass production of new materials may further enrich the research and application of functional materials. Herein, we controllably synthesized two series of novel mixed-halide Cs 3 Cu 2 Cl 5-x I x and Cs 5 Cu 3 Cl 8-x I x powders via the compositional engineering for the first time. The crystal structures are identified with Rietveld refinement and density functional theory calculations. The mixed-halide compound exhibits relatively wide full width of half-maximum (~70 nm), adjustable bandgap (from 449 nm to 486 nm), larger Stokes shifts (~200 nm), and dramatic improved stability with high efficiency (photoluminescence quantum yield at least 90.61%), which present a scalable strategy for mass production for practical applications. In addition, the controllable phase transformation from blue-emitting Cs 3 Cu 2 I 5 to yellow-emitting CsCu 2 I 3 was confirmed. Most notably, the white light is obtained by combining novel Cs 3 Cu 2 Cl 5-x I x /Cs 5 Cu 3 Cl 8-x I x with yellow-emitting CsCu 2 I 3 powders. Based on this, we firstly introduce the blue-emitting Cs 5 Cu 3 Cl 7 I powders in white LED fabrication by combining ultraviolet chip and as-prepared yellow-emitting CsCu 2 I 3 powders, to generate high-quality and stability white light with CIE coordinates of (0.335, 0.398) and colour rendering index value of 77.8. For comparison, red-emitting CaAlSiN 3 :Eu 2+ phosphors are also introduced for LED package to substitute CsCu 2 I 3 powders, which exhibit the high colour rendering index of 89.2. This work not only develops new mixed-halide compounds with high stability and performance, but also provides the unique strategy for promoting industrialization process of LED backlights.

White light-emitting diodes based on quaternary Ag–In-Ga-S quantum dots and their influences on melatonin suppression index

Light sources have effect on the circadian rhythms so as to the health of human. Therefore, both visual and non-visual effects should be considered when designing and fabricating light sources. Quantum dot (QD) materials have been extensively used as color converters to fabricate white light-emitting diodes (LEDs). However, most of the work on the photoluminescent QD-based LEDs (QLEDs) are focused on the improvement of visual performances. Here, quaternary Ag–In-Ga-S (AIGS)/ZnS QDs are synthesized for the application of white QLEDs taking both visual and non-visual performances into consideration. Theoretical calculation is carried out and the results show that QLEDs based on the combination of red emission QDs and green emission ones can exhibit a high color rendering index (CRI) of 90.8 and a color correlated temperature (CCT) of 5669 K, a melatonin suppression index (MSI) of 0.788. Furthermore, the combination of red 670 nm emission and green 550 nm AIGS/ZnS QDs are integrated with a blue-emission chip to fabricate QLEDs. The as fabricated devices exhibit a maximum CRI of 90.33, a CCT of 5947 K and an MSI of 0.7866, which are all consistent with the simulation results. These experimental results are comparable to those of some commercial white light sources. We discuss non-visual effects of QLEDs for the first time, and our research results show that AIGS/ZnS QDs, which are free-of heavy metal elements and have wide full-width of half maximums (FWHMs), are suitable for the fabrication white light sources with highly visual performances and tunable MSI values, which have many potential applications in the field of healthy lighting and environmentally friendly light sources.

Liquid/solution-based microfluidic quantum dots light-emitting diodes for high-colour-purity light emission

Organic light-emitting diodes (OLEDs) using a liquid organic semiconductor (LOS) are expected to provide extremely flexible displays. Recently, microfluidic OLEDs were developed to integrate and control a LOS in a device combined with microfluidic technology. However, LOS-based OLEDs show poor-colour-purity light emissions owing to their wide full width at half maximum (FWHM). Here we report liquid/solution-based microfluidic quantum dots light-emitting diodes (QLEDs) for high-colour-purity light emission. Microfluidic QLEDs contain liquid materials of LOS for a backlight and QDs solutions as luminophores. The microfluidic QLED exhibits red, green, and blue light emissions and achieves the highest light colour purity ever reported among LOS-based devices for green and red lights with narrow FWHMs of 26.2 nm and 25.0 nm, respectively. Additionally, the effect of the channel depth for the luminophore on the peak wavelength and FWHM is revealed. The developed device extends the capabilities of flexible microfluidic OLEDs-based and QDs-based displays.

The optical properties of a visible light filter integrated on the silicon substrate

There have been many investigations performed for color filtering based on surface plasmon resonances in recent years. However, research results on color filters integrated on the silicon-based photodetectors are infrequently reported. At present, problems including low light transmission, wide full width at half maximum (FWHM), and poor color tunability exist in the light filters integrated on the silicon-based photodetectors. We propose and numerically demonstrate a light filter with the periodic nanostructure and dielectric multi-layers integrated on the silicon substrate. Continuously tunable transmission visible spectra (400∼760 nm) are applied for the proposed filters. Hybrid resonant modes including plasmonic resonances and waveguide modes result in the extraordinary light transmission in the proposed filters. The simulations indicate that the integrated filter has more than 75% transmission and less than 25 nm full width at half maximum (FWHM) of the transmission curve for the destined wavelength. The proposed filter provides a solution for the combination of color filters with the silicon-based photosensors like CMOS photodiodes.