Commercial Blue Light-emitting Diode Research Articles

Efficient All‐Perovskite White Light‐Emitting Diodes Made of In Situ Grown Perovskite‐Mesoporous Silica Nanocomposites

AbstractMetal halide perovskite quantum dots (QDs) have emerged as potential materials for high brightness, wide color gamut, and cost‐effective backlight emission due to their high photoluminescence quantum yields, narrow emission linewidths, and tunable bandgaps. Herein, CsPbX3/SBA‐15 nanocomposites are prepared with outstanding optical properties and high stability through an in situ growth strategy using mesoporous silica particles. According to finite‐difference time‐domain simulations, the mesoporous structure provides a strong waveguide effect on perovskite QDs and the uniform dispersion suppresses reabsorption losses, improving the overall photoconversion efficiency of perovskite QDs. The as‐fabricated perovskite monochromatic light‐emitting diode (LED) has a maximum luminous efficiency of 183 lm W−1, which is the highest for monochromatic perovskite LEDs reported to date. A further benefit of this work is that the white devices, which combine the green and red perovskite nanocomposites with commercial blue LED, exhibit a high luminous efficiency of 116 lm W−1 and a wide color gamut (125% for NTSC and 94% for Rec. 2020) with coordinates of (0.33,0.31).

Full-Spectrum White Light-Emitting Diodes Enabled by an Efficient Broadband Green-Emitting CaY2ZrScAl3O12:Ce3+ Garnet Phosphor.

Phosphor-containing white light-emitting diodes (LEDs) with low color-correlated temperatures (CCTs) and high color rendering indexes (CRIs) are highly desirable for energy-efficient and environmentally friendly solid-state light sources. Here, we report a new and efficient blue light-excited, green-emitting Ce3+-activated CaY2ZrScAl3O12 phosphor, which underpins the fabrication of high-color quality and full-visible-spectrum warm-white LED devices with ultrahigh CRI values (Ra > 96 and R9 > 96). A family of CaY2ZrScAl3O12:Ce3+ phosphors with different Ce3+ dopant concentrations were prepared by high-temperature solid-state synthesis. X-ray diffraction and corresponding Rietveld refinement reveal a garnet structure with an Ia3̅d space group and crystallographic parameters a = b = c = 12.39645(8) Å, α = β = γ = 90°, and V = 1904.99(4) Å3. Luminescence properties were studied in detail as a function of Ce3+ with the optimal concentration 1% mol. Impressively, CaY2ZrScAl3O12:1%Ce3+ exhibits a broad excitation band from 370 to 500 nm, peaking at ∼421 nm, which is well matched with emission from commercial blue LED chips. Under 421 nm excitation, the CaY2ZrScAl3O12:1%Ce3+ phosphor produces dazzling green light in a wide emission band from 435 to 750 nm (emission peak: 514 nm; full width at half-maximum: 113 nm), with a high internal quantum efficiency of 63.1% and good resistance to thermal quenching (activation energy of 0.28 eV). A white LED device combining a 450 nm blue LED chip with CaY2ZrScAl3O12:1%Ce3+ green phosphor and commercial CaAlSiN3:Eu2+ red phosphor as color converters demonstrates bright warm-white light with excellent CIE color coordinates of (0.3938, 0.3819), low CCT of 3696 K, high CRI (Ra = 96.9, R9 = 98.2), and high luminous efficacy of 45.04 lm W-1 under a 20 mA driving current. New green phosphors enable the design and implementation of efficient luminescent materials for healthy solid-state lighting.

蓝光LED可激发的稀土掺杂SrS近红外二区纳米荧光 探针及温度传感

Lanthanide (Ln3+)-doped near infrared (NIR)-II luminescent nanoprobes have shown great promise in many technological fields, but are currently limited by the low absorption efficiency of Ln3+ due to the forbidden 4f→4f transition. Herein, we report a novel NIR-II luminescent nanoprobe based on efficient energy transfer from Ce3+ to Er3+ and Nd3+ in sub-10 nm SrS nanocrystals (NCs), which are excitable by using a commercial blue light-emitting diode (LED). Through sensitization by the allowed 4f→5d transition of Ce3+, the NCs exhibit strong NIR-II luminescence from Er3+ and Nd3+ with quantum yields of 2.9% and 2.3%, respectively. Furthermore, by utilizing the intense NIR-II luminescence of Er3+ from the thermally coupled Stark sublevels of 4I13/2, we demonstrate the application of SrS:Ce3+/Er3+ NCs as blue-LED-excitable NIR-II luminescent nanoprobes for ratiometric thermal sensing. These findings reveal the unique advantages of SrS:Ln3+ NCs in NIR-II luminescence, which may open up a new avenue for exploring novel and versatile luminescent nanoprobes based on Ln3+-doped sulphide NCs.

Experimental Demonstration of High-Sensitivity Underwater Optical Wireless Communication Based on Photocounting Receiver

In this paper, we propose a high-sensitivity long-reach underwater optical wireless communication (UOWC) system with an Mbps-scale data rate. Using a commercial blue light-emitting diode (LED) source, a photon counting receiver, and return-to-zero on–off keying modulation, a receiver sensitivity of −70 dBm at 7% FEC limit is successfully achieved for a 5 Mbps intensity modulation direct detection UOWC system over 10 m underwater channel. For 1 Mbps and 2 Mbps data rates, the receiver sensitivity is enhanced to −76 dBm and −74 dBm, respectively. We further investigate the system performance under different water conditions: first type of seawater (c = 0.056 m−1), second type (c = 0.151 m−1), and third type (c = 0.398 m−1). The maximum distance of the 2 Mbps signal can be extended up to 100 m in the first type of seawater.

Superoxide Ion and Singlet Oxygen Photogenerated by Metalloporphyrin-Based Metal-Organic Frameworks for Highly Efficient and Selective Photooxidation of a Sulfur Mustard Simulant.

The exploration of highly efficient materials for the degradation of chemical warfare agents has been a longstanding task for preventing human exposure. Herein, we report a series of metal-organic frameworks (MOFs) M-TCPP-La based on metallo-tetra(4-carboxyphenyl)porphyrin and LaIII, which were applied to selectively oxidize 2-chloroethyl ethyl sulfide (CEES, a sulfur mustard simulant) as heterogeneous photocatalysts. After irradiation from a commercial blue light-emitting diode (LED), both superoxide ion and singlet oxygen were generated by M-TCPP-La and involved in selective oxidization of CEES to 2-chloroethyl ethyl sulfoxide (CEESO). Notably, a very short half lifetime (2.5 min) was achieved using Fe-TCPP-La as the photocatalyst. In comparison to currently utilizing singlet oxygen and hydrogen peroxide as oxidizing agents, this work employing both singlet oxygen and superoxide ion represents a new and effective strategy of detoxification of mustard gas.

Multifunctional Pr3+ single doped CaLaMgTaO6: Crystal structure, thermal behavior and applications

This paper, for the first time, presents a comprehensive study of the structure, thermal stability and photoluminescence properties of CaLaMgTaO6:Pr3+ phosphors for LED applications. Pr3+ ions exhibits two clusters of dominant emissions peaked at 495 nm (3P0→3H4) and 657 nm (3P0→3F2) from double perovskite-structure CaLaMgTaO6 compounds. Meanwhile, the samples cover the emission wavelength of commercial blue light-emitting diode (LED) chips with high internal quantum efficiency (IQE) of 30.25% upon 450 nm excitation. The mechanism of thermal quenching for this phosphor was investigated and the corresponding activation energy ΔE was determined to be 0.23 eV. The fabricated Pr3+ single doped CaLaMgTaO6 together with a 450 nm blue LED chip is well-matched with the absorption band of photosynthesis, phototropism, and photomorphogenesis. Furthermore, this phosphor along with commercially available phosphors was applied to fabrication of 450 nm UV chip and YAG:Ce3+ emitted a well-distributed warm white light with high color rendering index (CRI) of 84.1 and a correlated color temperature (CCT) of 3914 K. All of the results indicate that this novel phosphor can compensate for the red light and has potential applications in plant cultivation and warm white LEDs field.

Preparation of red-emitting BaSiF6:Mn4+ phosphors for three-band white LEDs

BaSiF6:Mn4+ phosphors were synthesized to improve the color purity of phosphor-converted white light-emitting diodes (LEDs). The optimal synthesis conditions for attaining the brightest red emission spectrum from BaSiF6:Mn4+ were investigated. The BaSiF6:Mn4+ phosphor exhibited a strong absorption band at approximately 465 nm because of the 4A2g → 4T2g transition of Mn4+ ions. In addition, the phosphor exhibited three strong emission peaks, at 615, 632, and 650 nm, because of a combination of vibrational shifts and the 2Eg → 4A2g transition in Mn4+ ions. Thus, BaSiF6:Mn4+ is suitable for use as the red-emitting phosphor in three-band white LEDs pumped by a blue LED. The optical properties of BaSiF6:Mn4+ were examined under excitation from a commercial blue LED by coating the phosphor onto the blue LED. Similarly, a three-band white LED was also fabricated by coating the red-emitting phosphor BaSiF6:Mn4+ and green-emitting phosphor CsPbBr3 onto a commercial blue LED.

Temperature dependence of current–voltage and carrier lifetime characteristics in InGaN blue light-emitting diode

In this report, we have measured current–voltage (I–V) and carrier lifetime characteristics of an InGaN-based commercial blue light-emitting diode in a temperature range from 350 to 110 K. Two distinctly different current domains, namely, region I and region II have been identified in I–V dependence. I–V data for region I have been used for the evaluation of ideality factor which varies from 1.478 to 3.932 when the temperature changes from 350 to 110 K. We have also investigated how far the existing models account for our experimental results. From an analysis of the Arrhenius plot of I–V–T curves in terms of the model due to Hirsch and Barriere it is found that the domains are distinguished by current transport mechanisms governed by hole thermionic emission and hole tunneling which are discussed in detail. Next, estimating the data on voltage gradient obtained from the open circuit voltage decay method, as well as those of ideality factor from the I–V measurement, the temperature dependence of carrier lifetime has been evaluated. A logarithmic plot of carrier lifetime as a function of inverse temperature shows a weak temperature-dependence below 228 K and this region gives important information regarding the dominant energy level of traps assisting tunneling of current carriers in the device.

Nonlinear adaptive filters for high-speed LED based underwater visible light communication [Invited

Underwater visible light communication (UVLC) is expected to act as an alternative candidate in next-generation underwater 5G wireless optical communications. To realize high-speed UVLC, the challenge is the absorption, scattering, and turbulence of a water medium and the nonlinear response from imperfect optoelectronic devices that can bring large attenuations and a nonlinearity penalty. Nonlinear adaptive filters are commonly used in optical communication to compensate for nonlinearity. In this paper, we compare a recursive least square (RLS)-based Volterra filter, a least mean square (LMS)-based digital polynomial filter, and an LMS-based Volterra filter in terms of performance and computational complexity in underwater visible light communication. We experimentally demonstrate 2.325 Gb/s transmission through 1.2 m of water with a commercial blue light-emitting diode. Our goal is to assist the readers in refining the motivation, structure, performance, and cost of powerful nonlinear adaptive filters in the context of future underwater visible light communication in order to tap into hitherto unexplored applications and services.

An AIEgen-based 3D covalent organic framework for white light-emitting diodes

The design and synthesis of three-dimensional covalent organic frameworks (3D COFs) have still been considered as a big challenge. Here we report the design and synthesis of an AIEgen-based 3D COF (3D-TPE-COF), with a high surface area (1084 m2 g−1). According to powder X-ray diffraction and continuous rotation electron diffraction analyses, 3D-TPE-COF is identified to adopt a seven-fold interpenetrated pts topology. Interestingly, 3D-TPE-COF emits yellow fluorescence upon excitation, with a photoluminescence quantum yield of 20%. Moreover, by simply coating 3D-TPE-COF onto a commercial blue light-emitting diode (LED), a prototype white LED (WLED) under continuously driving without degradation for 1200 h was demonstrated. The present work suggests the possibility of using COF materials for stable WLEDs, which will greatly inspire us to design and synthesize fluorescent 3D COFs and facilitate the development of COF-based WLEDs in future.

Bright and Blue Nanocrystal Emitters

The discovery and development of blue light emitting diodes (LEDs) enabled energy-efficient white light emission that continues to impact global energy consumption today. Alternative materials that can outcompete commercial blue LEDs based on epitaxial InGaN could have a large impact on the lighting industry and in curbing anthropogenic climate change. Recently in Joule, Congreve and colleagues show that metal halide perovskite nanocrystals—greatly improved by Mn incorporation—have promise for low-cost, efficient, and bright blue LEDs.

Mechanism for Forming Quantum-Size AlGaN/GaN/InGaN/GaN Heterostructure Layers

The use of silicon in optoelectronic elements and microwave devices is limited by its electrical properties. In this range of application, silicon is replaced by wider-gap materials, e.g., GaN, AlN, InN, and solid solutions based on them. This allows highly efficient devices, including light-emitting diodes and photodetectors operating in a wide radiation spectral range, to be fabricated. In addition, GaN-based materials have been successfully used in designing high-power microwave devices, in particular, transistors with highly mobile electrons operating at high temperatures. We discuss specific features of the technology for fabricating active layers in the AlGaN/GaN/InGaN/GaN heterostructures with the use of metalorganic compounds. The initial substances used are ultra-pure ammonia NH3 and gallium, aluminum, and indium metalorganic compounds in the trimethyl form. The temperature dependence of the epitaxial GaN layer growth rate is investigated. This dependence is shown to be weak in a wide temperature range. The importance of adsorption processes occurring on the growth surfaces is confirmed. Thermodynamical analysis of the regularities of the investigated process is carried out to simulate the process and establish the conditions for forming GaN-based solid solutions. It is shown that during the formation of Ga1 – xInxN solid solutions in the high-temperature region the attainable InN content is not higher than 0.4 mole fractions. As the growth temperature decreases to 600°С, the conditions for incorporating In in the solid solution are noticeably improved and the InN concentration increases to 0.9 mole fractions. It is demonstrated that growing the GaAlN solid solutions in a wide temperature range makes it possible to obtain the AlN content ranging from 0.1 to 0.9 mole fractions. The experimental investigations are confirmed by the calculations. Therefore, when growing the Ga1 – xInxN quantum well layers in the active heterostructural area for commercial blue light-emitting diode chips with an indium content of х = 0.1–0.15, the growth temperature should be reduced. At low temperatures, however, it is difficult to grow epitaxial layers with a high crystal quality.

Stable White Light‐Emitting Biocomposite Films

AbstractThe demonstration of reliable and stable white light‐emitting diodes (LEDs) is one of the main technological challenges of the LED industry. This is usually accomplished by incorporation of light‐emitting rare‐earth elements (REEs) compounds within an external polymeric coating of a blue LED allowing the generation of white light. However, due to both environmental and cost issues, the development of low‐cost REE‐free coatings, which exhibit competitive performance compared to conventional white LED is of great importance. In this work, the formation of an REE‐free white LED coating is demonstrated. This biocomposite material, composed of biological (crystalline nanocellulose and porcine gastric mucin) and organic (light‐emitting dyes) compounds, exhibits excellent optical and mechanical properties as well as resistance to heat, humidity, and UV radiation. The coating is further used to demonstrate a working white LED by incorporating it within a commercial blue LED.

Photoluminescence and electric properties of Pr/Nb codoped Bi4Ti3O12 bismuth layered-structure ceramics

Bi4Ti3O12 (BIT) belongs to bismuth-layer structure piezoelectric materials, along with high Curie temperature ( T c) and high resistivity. Pr/Nb co-doped BIT piezoelectric ceramics were synthesized by conventional solid-state reaction method and their structural, up-conversion luminescent and dielectric properties were investigated in this study. The substitution of Nb5+ ion was fixed as 0.08 mol and the amount of Pr3+ was 0≤ x ≤0.1. The X-ray diffraction data showed that the samples were single phase with orthorhombic unit cell, and SEM micrographs revealed that the samples have similar plate-like grain morphology. Raman spectroscopy revealed that Er3+ substitution for Bi3+ occured predominantly at the A-site in the perovskite blocks. The red emission was observed under the ultraviolet and blue light excitation at room temperature, which is adaptable to the emission band of commercial blue light-emitting diodes (LEDs) chips. With increasing Pr3+ content, the intensity of the photoluminescence increased initially and then decreased due to concentration quenching. The T c was slightly shifted to the lower temperature, the piezoelectric and ferroelectric properties was both enhanced by doping. These results indicated the Pr doped BITN ceramics were a kind of multifunctional materials with excellent optical performance.

A Flexible and Transparent Graphene-Based Triboelectric Nanogenerator

This paper presents a new high-output, flexible and transparent nanogenerator using chemical vapor deposition grown graphene as one of the friction layer. Graphene on copper is transferred onto polyethylene terephthalate by wet transfer method makes graphene-based triboelectric nanogenerator (TENG) have electrical conductivity and high optical transmittance. We have fabricated plasma treated thin layer of polydimethylsiloxane structure as another layer to improve the output performance of nanogenerator. Using this graphene-based TENG, maximum output voltage 650 V and current 12 μA is achieved at 4.3 Hz frequency. As a power source, LCD and 50 commercial blue light-emitting diodes are lighted up. It is low cost, simple, and robust approach for harvesting ambient vibration energy.

Large-scale synthesis of single-source, thermally stable, and dual-emissive Mn-doped Zn–Cu–In–S nanocrystals for bright white light-emitting diodes

The global demand for resource sustainability is growing. Thus, the development of single-source, environment-friendly colloidal semiconductor nanocrystal (NC) phosphors with broadband emission spectra is highly desirable for use as color converters in white light-emitting diodes (WLEDs). We report herein the gram-scale synthesis of single-source, cadmium-free, dual-emissive Mn-doped Zn–Cu–In–S NCs (d-dots) by a simple, non-injection, low-cost, one-pot approach. This synthesis method led to the formation of NCs with continuously varying compositions in a radial direction because each precursor had a different reactivity. Consequently, the d-dots exhibited two emission bands, one that could be attributed to Mn emission and a second that could be ascribed to the band edge of the Zn–Cu–In–S NCs. The emission peaks assigned to band edge were tunable by modifying the particle size and composition. The prepared d-dots also exhibited the characteristic zero self-absorption, a quantum yield of 46%, and good thermal stability. Combining a commercial blue light-emitting diode (LED) chip with optimized d-dots as color converters gave a high color rendering index of up to 90, Commission Internationale de l’eclairage color coordinates of (0.332, 0.321), and a correlated color temperature of 5,680 K. These results suggest that cadmium-free, thermally stable, single-phase d-dot phosphors have potential applications in WLEDs.

Freestanding CNT–WO3hybrid electrodes for flexible asymmetric supercapacitors

The CNT//CNT–WO3asymmetric supercapacitor reaches a power density of 30.6 mW cm−3and retains 75.8% after 50 000 cycles.

An organic down-converting material for white-light emission from hybrid LEDs.

A novel BODIPY-containing organic small molecule is synthesized and employed as a down-converting layer on a commercial blue light-emitting diode (LED). The resulting hybrid device demonstrates white-light emission under low-current operation, with color coordinates of (0.34, 0.31) and an efficacy of 13.6 lm/W; four times greater than the parent blue LED.

Strong photoluminescence and piezoelectricity properties in Pr-doped Ba(Zr0.2Ti0.8)O3–(Ba0.7Ca0.3)TiO3 ceramics: Influence of concentration and microstructure

(Ba0.85Ca0.15)1−xPrx(Zr0.1Ti0.9)O3 (where 0 < x < 0.01, abbreviated as BCZT:xPr) ceramics were fabricated by conventional solid-state reaction method. The influence of dopant concentration and microstructure on photoluminescence, ferroelectric, and piezoelectric properties was systematically investigated. The results showed that the photoluminescence spectra of the samples exhibited strong green (530 nm) and red (602 nm) emissions upon excitation of the 430 nm to 500 nm light, which couples well with to the emission band of the commercial blue light-emitting diodes chips. The emission intensities were strongly dependent on the dopant concentration and crystallite size, which reached the optimal value when the crystallite size and dopant concentration were 8 μm and 0.002 mol, respectively. Meanwhile, a large piezoelectric response with d33 = 325 pC/N was obtained for BCZT:0.002Pr near the morphotropic phase boundary. Therefore, the Pr-doped BCZT materials, simultaneously exhibiting excellent luminescent properties and high piezoelectric properties, may have significant technological promise in novel multifunctional devices.

Green and red emission for (K0.5Na0.5)NbO3:Pr ceramics

The photoluminescence properties of Pr-doped K0.5Na0.5NbO3 (KNN) ceramics were prepared by the solid-state reaction method and investigated as a function of Pr concentration and sintering temperature. The excitation band ranging from 430 to 500 nm covers the emission wavelength of all commercial blue light-emitting diode chips. The photoluminescence spectra of KNN:Pr exhibit strong green (528 nm) and red (617 nm and 650 nm) emissions. The optimum doping concentration of Pr in KNN is 0.5 mol. %, and the optimized sintering temperature is 1170 °C. In addition to the admirable intrinsic piezoelectric properties of KNN, Pr-doped KNN may take an important role in many fields as a multifunctional material.