Excellent Luminous Efficiency Research Articles

Antimony doping towards fast digital encryption and decryption and high-efficiency WLED in zero-dimensional hybrid indium chlorides

Lead-free metal halides with thermally induced reversible fluorescence transitions are promising smart optoelectronic materials. However, it is challenging to obtain such materials with reversible and fast fluorescent thermochromism at relatively low temperatures. Herein, two series of new zero-dimensional (0-D) hybrid perovskite indium chlorides doped with Sb3+ are synthesized and characterized, namely (TAEA)InCl6·Cl·4H2O: xSb3+ (1: xSb3+) and (TETA)InCl6·Cl·H2O: xSb3+ (2: xSb3+) (TAEA = quadruply protonated tris(aminoethyl)amine; TETA = quadruply protonated triethylenetetramine; x = 0 − 15 %). Compound 1: 0.5 %Sb3+ displays green broadband emission with photoluminescence quantum yield (PLQY) of 44.4 %, while compound 2: 1 %Sb3+ produces yellow emission with PLQY of 73.46 %. A reversible transition between green and orange light emission for 1: 0.5 %Sb3+ can be triggered by thermal stimulation; such photoluminescence (PL) color switching happens with a fast response time of 20 s and a low transition temperature of 333 K. In addition, the materials combining compounds 2: 1 %Sb3+ and 1: 0.5 %Sb3+ can achieve complex digital encryption and decryption upon heating. Furthermore, due to its excellent luminous efficiency, the 2: 1 %Sb3+ is employed as yellow phosphor for white light-emitting diode (WLED). The WLED shows a CRI of 90.5 and a CCT of 5415 K, superior to most WLEDs based on hybrid metal halides. Finally, the impact of forming the self-trapped excitons state and complex PL mechanism of compound 1: 0.5 %Sb3+ are investigated through DFT calculations and femtosecond transient absorption techniques. This work provides new insights into the design of hybrid metal halides with multiple optical properties, paving the way to obtaining materials for multiple optical applications.

Higher chromatic rendition with Cr<sup>3+</sup>-doped yellow Y<sub>3</sub>Al<sub>5</sub>O<sub>12</sub>:Ce<sup>3+</sup> for double-layer remote phosphor white-light-emitting diodes

<span lang="EN-US">Remote phosphor designs of white-light-emitting diodes (WLEDs) have been recognized for their high thermal stability and excellent luminous efficiency but not for the chromatic rendering. The study presents an approach for the remote phosphor structure to overcome the low-color-rendering issue by enriching its red-light spectral intensity through co-doping </span>Cr<sup>3+</sup> and Ce<sup>3+</sup> <span lang="EN-US">ions into the yellow </span> Y<sub>3</sub>Al<sub>5</sub>O<sub>12 </sub>(YAG) <span lang="EN-US">phosphor compound. This ion co-doping process probably enhances emission spectra in the far-red range because of the energy transfer of the integrated ions:</span> Ce<sup>3+</sup> Cr<sup>3+</sup>. <span lang="EN-US">Additionally, the luminescence and color properties of the phosphor layer significantly depend on the doped concentration of the</span> Cr<sup>3+</sup> ion. Here, with 0.008% Cr<sup>3+</sup> <span lang="EN-US">in the phosphor composite, either internal or external quantum performances of the dual-layer WLED light are enhanced, which achieved the number of 58.9% and 46.7%, respectively. The color rendering index (CRI) would also be higher if </span>Cr<sup>3+</sup> <span lang="EN-US">is added, about 77.9, compared to the CRI of 63.2 when using the original </span> YAG:Ce<sup>3+</sup> phosphor layer.

Advances and Challenges in Heavy-Metal-Free InP Quantum Dot Light-Emitting Diodes.

Light-emitting diodes based on colloidal quantum dots (QLEDs) show a good prospect in commercial application due to their narrow spectral linewidths, wide color range, excellent luminance efficiency, and long operating lifetime. However, the toxicity of heavy-metal elements, such as Cd-based QLEDs or Pb-based perovskite QLEDs, with excellent performance, will inevitably pose a serious threat to people’s health and the environment. Among heavy-metal-free materials, InP quantum dots (QDs) have been paid special attention, because of their wide emission, which can, in principle, be tuned throughout the whole visible and near-infrared range by changing their size, and InP QDs are generally regarded as one of the most promising materials for heavy-metal-free QLEDs for the next generation displays and solid-state lighting. In this review, the great progress of QLEDs, based on the fundamental structure and photophysical properties of InP QDs, is illustrated systematically. In addition, the remarkable achievements of QLEDs, based on their modification of materials, such as ligands exchange of InP QDs, and the optimization of the charge transport layer, are summarized. Finally, an outlook is shown about the challenge faced by QLED, as well as possible pathway to enhancing the device performance. This review provides an overview of the recent developments of InP QLED applications and outlines the challenges for achieving the high-performance devices.

A stochastic DNA walker electrochemiluminescence biosensor based on quenching effect of Pt@CuS on luminol@Au/Ni-Co nanocages for ultrasensitive detection of I27L gene

The common I27L mutations of the hepatocyte nuclear factor-1α (HNF1A) significantly increase the incidence of maturity-onset diabetes of the young (MODY). Hence, the establishment of an ultrasensitive detection strategy for I27L gene is crucial for the diagnosis and treatment of MODY. Herein, a signal-off electrochemiluminescence resonance energy transfer (ECL-RET) biosensor with effective target-induced stochastic DNA walker amplification was fabricated for I27L detection. In this biosensor, Prussian blue analogues (Ni-Co) nanocages/Au-supported luminol (luminol@Au/Ni-Co) were used as ECL donors and exhibited excellent luminous efficiency. On the other hand, Pt nanoparticles-grown on copper sulphide (Pt@CuS) were used as energy acceptors to quench the initial signal based on RET between luminol and CuS. Moreover, the autonomous locomotion of I27L assisted by Exo III is the key in this DNA walker biosensor, as it continually induces new digestion processes on the electrode surface and quenches signals caused by the introduction of numerous acceptors. The efficient donor/acceptor pairs and DNA walker amplification system of the ECL-RET allowed the proposed biosensor to effectively detect I27L with a wide linear range of 0.0001 to 100 nM and a limit of detection as low as 23 fM. Thus, the ECL-RET biosensor provides a promising sensing platform for the diagnosis and typing of diabetes.

The excellent luminous efficiency and high thermal stability of phosphor-in-glass for high-power laser

At present, fluorescent glass mainly emits a single yellow light. The characteristic of green and red luminescent materials limits its omni-directional combination with yellow light materials, resulting in high correlated color temperature and low color rendering index of laser lighting devices, which seriously reduces the quality of laser lighting. Therefore, the development of multi-color fluorescent glass to improve the color quality is a huge challenge in laser lighting technology. In this research, the glass matrix that can be compounded with multi-color phosphors is proposed to solve the problems of phosphor decomposition, oxidation, corrosion, and blackening during the vitrification process. Surprisingly, a 50 wt. % Ce:YAG&1.5 wt. % CaAlSiN3-PiG (50 Y&1.5 R-PiG) sample exhibits an excellent internal quantum efficiency of 94% and achieves a high luminous efficiency of 184 lm/W under laser irradiation. Moreover, an ultrahigh luminous efficiency of 331 lm/W is realized by using a laser device with a heat sink. It demonstrated that Y&R-PiG can own excellent application prospects in high-quality lighting fields, such as laser displays and automobile headlights.

Ultrastable Perovskite Nanocrystals in All‐Inorganic Transparent Matrix for High‐Speed Underwater Wireless Optical Communication

AbstractThe key features of lead halide perovskites, including short emission lifetime and excellent luminous efficiency in the green emission region, perfectly match the strict requirements of underwater wireless optical communication (UWOC). However, the poor stability of perovskite nanocrystals (NCs) restricts its application under water and no relevant application research has been reported. Here, extremely stable CsPbBr3 NCs in all‐inorganic amorphous glass synthesized by all‐solid reaction without any organic ligand are reported. The products achieve high photoluminescence quantum yield (70%) as well as excellent stability toward water, thermal treatment (200 °C in air) and intensive laser irradiation (3.6 kW cm−2). The authors also raise that the refraction index could strongly influence the lifetime values according to the oscillator strength of radiative transitions. The large refraction index of the glass matrix enhances the radiative transition rates of CsPbBr3 NCs (decay time 3.22 ns). At last, the first application of perovskite NCs for UWOC is demonstrated, achieving a bandwidth as high as 180 MHz and data rates of 185 Mbps.

High lumen density of Al2O3‐LuAG: Ce composite ceramic for high‐brightness display

AbstractThermally robust and highly efficient green‐emitting luminescent ceramics are gradually attracting great attention as promising phosphors using in high‐brightness laser phosphor display to reduce serious speckle noise as well as high cost. However, lumen density is still seriously restricting their potential applications especially under high‐power density laser due to insufficient absorption of blue laser and significant thermal quenching. Here, we report an Al2O3‐LuAG: Ce composite ceramic phosphor (CCP) for high‐brightness laser phosphor display. Owing to good optical properties and high thermal conductivity of Al2O3, the Al2O3‐LuAG: Ce CCP shows high photoluminescence quantum yield (79.6%), low thermal quenching (only 3.2% loss in luminescence at 200°C), and high thermal conductivity (18.9 W·m−1·K−1). Moreover, the Al2O3, as scattering centers, enhances the Rayleigh–Mie scattering of the blue laser, and hence the absorption of the Al2O3‐LuAG: Ce CCP exhibits a remarkable improvement (~2.3 times) at 450 nm. Finally, with optimized thickness (0.3 mm) of Al2O3‐LuAG: Ce CCP, an excellent luminous efficiency (216 lm·W−1) and outstanding lumen density (6129 lm·mm−2) of the green‐emitting light source was obtained by driving under a high‐power density (28.33 W·mm−2) blue laser. All of those validate the suitability of the Al2O3‐LuAG: Ce CCP for high‐brightness display.

Emission tunable of Mg0.695Si0.695Al1.39O3.65N0.35:Eu2+,Mn2+ oxynitride phosphors via energy transfer for WLEDs

A series of Eu2+ doped and Eu2+/Mn2+ co-doped Mg0.695Si0.695Al1.39O3.65N0.35 (MSAON) phosphors were synthesized by solid-state reaction at a lower temperature of 1500 °C. The crystal morphology and structure of MSAON host were characterized by SEM, TEM and XRD. The quantum yield (QY) for Eu2+ doped MSAON phosphors was measured as high as 62%, indicating the excellent luminous efficiency. For the Eu2+/Mn2+ co-doped MSAON phosphor, the photoluminescence spectrum and delay curves reveal the efficient energy transfer (ET) process from Eu2+ to Mn2+ ions. Meanwhile, the corresponding energy transfer efficiency, critical distance and mechanism are discussed in detail. Temperature-dependent emission spectrum shows the thermal and color stabilities. The emission color of MSAON:Eu2+,Mn2+ phosphors could be tuned from blue through white to red via varying the concentration of Mn2+ ions. White-light-emitting diodes (WLEDs) were successfully fabricated by encapsulating the phosphors in n-UV LED (365 nm) devices obtaining white light with color rendering index (CRI) as high as 87.7. The results reveal that the MSAON:Eu2+,Mn2+ phosphors could have potential application in the field of n-UV WLEDs.

Poly-silicon light-emitting-device based electro-optical interfaces in standard silicon-CMOS integrated circuitry

A silicon-based light source using simple manufacturing process and having excellent luminous efficiency is significantly desired for the development of optoelectronic integrated circuits. In this paper, an integrated poly-silicon avalanche mode light-emitting-device (poly-SiAMLED) is fabricated using a complementary metal oxide semiconductor (CMOS) process. It utilizes the poly-silicon p-n junctions in avalanche breakdown to achieve illumination and employs the carrier injection technology to achieve about 2.9 × 10−7 external quantum efficiency and about 2.2 × 10−8 power conversion efficiency. Moreover, it is easy to fabricate because the process is compatible with the existing integrated circuit process. The proposed device can be used as one of the components of the optoelectronic interface in optoelectronic integrated circuits.

Discrete Conjugated Poly(arylene ether) Compounds for Blue Emission Electroluminescent Devices

Conjugated polymers with discrete units have received attention for their potential applications in molecular electronics and photonics. This study, a series of fluorinated carbazole derivatives of a discrete conjugated main chain, which integrated anthracene and pyrene groups, was reported. Three polymers, namely PCzAn, PCzBAn, and PCzPy, were designed and synthesized through Suzuki and poly coupling reactions, and the conjugation of the geometry of these materials was investigated. These molecules were characterized using 1H nuclear magnetic resonance, Fourier transform infrared (FTIR) spectroscopy, gel permeation chromatography (GPC)-mass spectrometry, PL spectrum, absorption spectrum, PLQY, and solution-processed for OLEDs. All materials showed remarkable thermal stability and excellent quantum efficiency. In the emitting layer, the blending of PCzBAn:PVK (8:2) exhibited excellent luminance efficiency and external quantum efficiency of 4.87 cd/A and 2.89%, respectively.

Excellent luminous efficiency and high thermal stability of glass-in-LuAG ceramic for laser-diode-pumped green-emitting phosphor.

A kind of glass-in-LuAG (GIP) ceramic with excellent luminous efficiency and high thermal stability was fabricated by solid-state sintering for laser diode (LD)-pumped green-emitting phosphor. The GIP ceramic employing particularly designed borosilicate glass as adhesive exhibits high thermal conductivity (2.8 W/m·K at 80°C) and remarkable improvement in thermal stability (Tg=711°C) and reliability (luminous flux has only a 0.5% drop after 100h at 300°C). When the GIP ceramic is pumped by 455nm blue LDs (14.5 W/mm2), a luminous efficacy of 205lm/W was achieved. More importantly, the GIP ceramic did not have luminescence saturation even under a higher power density (17.1 W/mm2) excitation. The novel GIP ceramic, possessing good optical and thermal properties, is promising for LD-pumped green-emitting phosphor.

Y/Gd-free yellow Lu3Al5O12:Ce3+ phosphor for white LEDs

Solid solubility limit of Ce3+ ions into Lu-based garnet, Lu3(1−x)Ce3xAl5O12, was determined as below 6.7mol% (3x<0.2mol) through Raman spectra and X−ray diffraction patterns. Above the solid solubility limit (3x≥0.2mol), Lu3(1−x)Ce3xAl5O12 phosphors showed the significant redshift to the yellow spectral region without Y3+ and Gd3+ ions. The redshift was explained in terms of the local compressive strain at the Ce3+ sites. The optimized sample (3x=0.4mol) had a dominant emission wavelength of 548nm, color coordinate of CIEx=0.421, CIEy=0.548, quantum efficiency of 80%, absorbance of 91%, lumen maintenance of 90% and high color stability at 473K under 450nm excitation wavelength, suggesting substitutability for the commercial yellow (Y, Gd)3(Al, Ga)5O12:Ce3+ phosphor. The measured decay times at higher Ce3+ concentration are significantly shortened at higher temperature than that of those at lower Ce3+ concentration. The yellow Lu2.6Ce0.4Al5O12 and a commercial red (Sr, Ca)AlSiN3:Eu2+ phosphor were applied to the pc-WLED, it gave an excellent luminous efficiency (138lm/W) with a slightly lower color rendering index (Ra=76.4) under correlated color temperature of 6500K compared to those of the (Y, Gd)3(Al, Ga)5O12:Ce3+-based one (136lm/W, Ra=78.7). Especially, the quantities of the used phosphors were significantly decreased by 20% for the yellow LuAG:Ce and by 40% for the red (Sr, Ca)AlSiN3:Eu2+. Thus, the Y/Gd−free pure LuAG:Ce yellow phosphors can be used as alternative to the commercial yellow YAG:Ce phosphor.

Highly efficient new hole injection materials for organic light emitting diodes base on phenothiazine derivatives.

New hole injection materials for OLED based on phenothiazine were synthesized, and the electro-optical properties of synthesized materials were examined by through UV-Vis. and photoluminescence spectroscopy as well as cyclic voltammetry. 1-NDD-t-BPBP and 2-NDD-t-BPBP showed Tg of 180 and 177 °C. These are higher than that (110 °C) of 2-TNATA, commercial HIL material. As for the HOMO level of the synthesized materials, 1-NDD-t-BPBP and 2-NDD-t-BPBP were 4.99 and 5.02 eV, indicating well-matched values between HOMO (4.8 eV) of ITO and HOMO (5.4 eV) of NPB, HTL material. In addition, judging from the fact that the synthesized materials both barely showed any absorption in the range of over 450 nm, the synthesized materials could be effectively used as an HIL material. The synthesized materials were used as the HIL in OLED device, yielding luminance efficiencies of 4.51 cd/A (1-NDD-t-BPBP) and 4.44 cd/A (2-NDD-t-BPBP). These results indicated that 1-NDD-t-BPBP shows more excellent luminance efficiency which is about 11% improved over 2-TNATA a commercial HIL material.

Highly efficient and stable deep-blue emitting anthracene-derived molecular glass for versatile types of non-doped OLED applications

New anthracene-based deep-blue emitting molecular glass, 9-(9-phenylcarbazole-3-yl)-10-(naphthalene-1-yl)anthracene (PCAN), which is asymmetrically functionalized with N-phenylcarbazole and naphthalene, has been designed, synthesized, and characterized. The deep-blue emitting PCAN is efficiently secured for color purity, has high glass transition temperature (Tg = 151 °C), and has excellent solubility (>100 mg mL−1 in toluene), due to its highly tilted asymmetric molecular conformation. Using processing versatility of PCAN, vacuum-deposited and solution-processed non-doped deep-blue fluorescent organic light-emitting diodes (OLEDs) were prepared, which employ PCAN as an emitter. The vacuum deposited, non-doped EL device exhibited not only the excellent luminance efficiency and external quantum efficiency (as high as 3.64 cd A−1 and 4.61%, respectively) for the saturated deep-blue CIE chromaticity coordinates of (0.151, 0.086), but also stable performance and a good device lifetime. Furthermore, the solution processed EL device also exhibited an encouraging level of performance (1.24%, 1.15 cd A−1) and deep-blue emission (0.159, 0.105).

Synthesis and Photoluminescent Properties of Violet Emitting 5,6‐Diphenylfuro[2,3‐d]pyrimidine Derivatives.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Synthesis and Photoluminescent Properties of Violet Emitting 5,6-Diphenylfuro[2,3-d]pyrimidine Derivatives

Furopyrimidines have known to possess antitumor, analgesic, antihypertensive, anti-inflammatory activity, and to inhibit adenosine kinase in very low concentration. Recently, we found that various furopyrimidine derivatives had optical properties to apply for organic light-emitting diodes (OLED) or fluorescent dye. Organic electroluminescent diode has undergone dramatic improvement since pioneering work of Tang and VanSlyke. Much progress has made especially in recent year, including the development of device fabrication, good material, and construction of manufacture infrastructure. It is necessary to have a set of red, green, and blue emitting materials with excellent luminous efficiency, proper chromaticity and the photochemical stability of emitters for an emitting layer for OLED. Though many organic, polymeric and inorganic emitting materials have been reported, many breakthroughs have to be achieved on the field of materials for excellent efficiency of OLEDs. Therefore, we report the synthesis of furopyrimidine derivatives and their photoluminescent properties. Furopyrimidines (1-9) were obtained in high yield in five steps, starting from the reaction of furoin with malonitrile in the presence of diethyl amine, as shown in Scheme 1. The absorption spectra and photoluminescent spectra of the compounds (1-9) were monitered using dichloromethane on the concentration of 50 μM by UV/Vis spectroscopy and luminescent spectroscopy, and their results were showed in Table 1 and typical example of spectrum was shown in Figure 1 for 1, 5 and 7. The full widths at half maximum value of all compounds were between 59 and 91 nm, showing generally good color purity. Thermogravimetric analysis (TGA, 50-500 C, 20 C/min, N2) of 5 showed an onset of weight loss at 243 C, 10% weight loss at 270 C, and over 90% weight loss 382 C. The onset temperature of weight loss of compounds 1-4 and 6-9 were between 210 and 250 C. All furopyrimidine derivatives (1-9) displayed intenser photoluminescence (PL) in concentration of 50 μM CH2Cl2

Radiation damage and transmission enhancement in surface-emitting organic light-emitting diodes

A systematic study has been carried out on organic light-emitting diodes (OLEDs) with a transparent MgAg/ITO cathode. The most dominant imperfections in surface-emitting OLEDs were electrical shorts and attributed to radiation damage incurring in ITO deposition due to the presence of pinholes in the MgAg protective layer. When adding an ITO surface layer on a semitransparent MgAg thin film, an increase in luminance efficiency was observed and exhibited a strong dependence on ITO thickness. By carefully selecting processing conditions and device layer structures we fabricated surface-emitting OLEDs with excellent luminance efficiency and good operational stability.

Efficient light-emitting diodes based on a binaphthalene-containing polymer

We report an efficient electroluminescent device using a binaphthalene-containing polymer as the emissive layer and a fluorinated copper phthalocyanine as the electron injecting/transporting layer. The structural feature of this polymer is a twisted, nonplanar backbone with two hexyloxy side groups. The energy levels for the highest occupied molecular orbital and the lowest unoccupied molecular orbital of this polymer were −5.71 and −2.38 eV as determined by cyclic voltammetry and ultraviolet-visible measurements. A light-emitting diode with aluminum electrode exhibited high brightness (9400 cd/m2 at 24.3 mA/cm2), excellent luminous efficiency (4.9 lm/W), and a large external quantum efficiency (2.0%).