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Highly Efficient and Bright Inverted Top‐Emitting InP Quantum Dot Light‐Emitting Diodes Introducing a Hole‐Suppressing Interlayer
摘要： InP quantum dots (QDs) based light-emitting diodes (QLEDs) are considered as one of the most promising candidates as a substitute for the environmentally toxic Cd-based QLEDs for future displays. However, the device architecture of InP QLEDs is almost the same as the Cd-based QLEDs even though the properties of Cd-based and InP-based QDs are quite different in their energy levels and shapes. Thus, it is highly required to develop a proper device structure for InP-based QLEDs to improve the efficiency and stability. In this work, efficient, bright, and stable InP/ZnSeS QLEDs based on an inverted top emission QLED (ITQLED) structure by newly introducing a “hole-suppressing interlayer” are demonstrated. The green-emitting ITQLEDs with the hole-suppressing interlayer exhibit a maximum current efficiency of 15.1–21.6 cd A?1 and the maximum luminance of 17 400–38 800 cd m?2, which outperform the recently reported InP-based QLEDs. The operational lifetime is also increased when the hole-suppressing interlayer is adopted. These superb QLED performances originate not only from the enhanced light-outcoupling by the top emission structure but also from the improved electron–hole balance by introducing a hole-suppressing interlayer which can control the hole injection into QDs.
关键词： indium phosphide,top emitting structure,efficiency,quantum dot–based light emitting diodes (QLEDs),hole suppressing interlayer
更新于2025-09-12 10:27:22
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[IEEE 2019 21st International Conference on Transparent Optical Networks (ICTON) - Angers, France (2019.7.9-2019.7.13)] 2019 21st International Conference on Transparent Optical Networks (ICTON) - Towards Solution-Processed Top-Emitting OLEDs Using a Phosphorescent Iridium Complex
摘要： Phosphorescent inverted top-emitting OLEDs using green iridium complexes have been fabricated by spin coating and their performances compared to bottom-emitting OLEDs based on the same materials. Even if the current efficiency is lower, respectively 7.0 ± 1.1 cd.A-1 and 12.9 ± 1.9 cd.A-1, this paper demonstrates the feasibility to fabricate phosphorescent top-emitting OLEDs by using a solution process with a simple OLED structure and replacing indium tin oxide electrode by a low-cost reflective aluminum electrode. Optical characterization of the top-emitting OLEDs shows a low emission shift compared to the spectrum of bottom-emitting OLED. A low angle dependency of the electroluminescence peak wavelength is observed , showing it is possible to control and minimize the microcavity effects for solution-processed top-emitting OLEDs.
关键词： phosphorescent emitters,solution process,top-emitting organic light-emitting diodes (OLEDs)
更新于2025-09-12 10:27:22
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Polarized monolithic white semipolar (20–21) InGaN light-emitting diodes grown on high quality (20–21) GaN/sapphire templates and its application to visible light communication
摘要： We demonstrate efficient, polarized and monolithic white semipolar (20–21) InGaN light-emitting diodes (LEDs) grown on high crystal quality 4-inch (20–21) GaN/sapphire template. Materials growth by metal-organic chemical vapor deposition (MOCVD) and characterization by atom probe tomography (APT) were carried out. The fabricated regular 0.1 mm2 size LEDs show a high electrical performance with an output power of 3.9 mW at 100 mA, an emission spectrum with two peaks located at 445 nm and 565 nm, a CIE point of (0.37, 0.42) and a polarization ratio of 0.30, which make them promising candidates for backlighting in liquid crystal displays (LCDs) application. Moreover, the fabricated square phosphor-free white μLED with size ranging from 20 to 60 μm, exhibit a high 3 dB modulation bandwidth of 660 MHz in the visible light communication (VLC) system, which benefits from the shorter carrier lifetime grown on the semipolar (20–21) plane. To our best knowledge, this is the first demonstration of monolithic white semipolar μLEDs in the VLC application, which can overcome the limitation of the slow frequency response of yellow phosphors converted commercial white LEDs. These results demonstrate the huge potentials to produce high efficiency monolithic white semipolar InGaN LEDs on cost-effective large area sapphire substrates.
关键词： Polarization,Light-emitting diodes,Atom probe tomography,Semipolar GaN,Visible light communication
更新于2025-09-12 10:27:22
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White-light/tunable emissions in single-phased BaLa2Si3O10:Eu3+, Bi3+ phosphor for the simultaneous applications in white light-emitting diodes and luminous cement
摘要： In this work, we report the single-phased BaLa2Si3O10:Eu3+, Bi3+ phosphor with white-light/tunable emissions under UV excitations. We find the emissions of Bi3+-doped BaLa2Si3O10 samples are dependent on the excitation spectral wavelength, where exciting by the wavelength from 240 to 410 nm range can lead to the tunable Bi3+ emissions owing to the intensity change of three emission bands (i.e., 367 nm, 423 nm, and 516 nm). After co-doping the Eu3+ ions into Bi3+-doped BaLa2Si3O10, the energy transfer from Bi3+ to Eu3+ ions dominated by a dipole–quadrupole (d–q) interaction mechanism is proved. Typically, by exciting with 365 nm and varying the Eu3+ content, the tunable emissions from blue, white to red are observable in the BaLa2Si3O10:Eu3+, Bi3+. By coating the white BaLa2Si3O10:Eu3+, Bi3+ sample with a commercial 365-nm UV LED chip or mixing it with the cement, we not only achieve the white-light LEDs device with the desirable color rendering index (CRI) of 95, excellent luminescent efficiency of 80 lm/W, and good excellent color temperature (CT) of 4215 K at the CIE chromaticity of (0.338, 0.357), but also achieve the luminous cement.
关键词： white light-emitting diodes,single-phased phosphor,white-light/tunable emissions,luminous cement,BaLa2Si3O10:Eu3+,Bi3+
更新于2025-09-12 10:27:22
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[IEEE 2019 3rd International Conference on Trends in Electronics and Informatics (ICOEI) - Tirunelveli, India (2019.4.23-2019.4.25)] 2019 3rd International Conference on Trends in Electronics and Informatics (ICOEI) - Performance analysis of LEDs in MIMO-OFDM based VLC indoor communication
摘要： The combination of Visible Light Communication (VLC) and Multiple-Input Multiple-Output (MIMO) is used for high-data-rate indoor wireless communications. Because the traditional RF communication systems are not capable of satisfying the growing wireless communication systems. The dual function of light-emitting diodes (LEDs), such as illumination and communication to evaluate while implementing MIMO-VLC system. The LED-based VLC system has several advantages such as security, cost-effectiveness and lack of interference. In this work, the VLC system is used in an indoor environment. The LED lamps are placed at the ceiling to provide ambient light which offers rich spatial resources for VLC. Here, various LEDs such as phosphor-converted led, organic led, micro led, RGB led and white led are used and the performance of LEDs are analyzed. The type of receiver used in the MIMO VLC system is Avalanche Photodiode Detector (APD). The performance of LED is analyzed by luminous flux, luminous efficacy, switching time, data rate and brightness.
关键词： luminous efficacy,Visible light communication,multiple-input multiple-output,data rate,light-emitting diodes
更新于2025-09-12 10:27:22
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Tetraphenylimidazole-based luminophores for explosive chemosensors and OLEDs: experimental and theoretical investigation
摘要： Four different small molecular weight tetraphenylimidazole (TPI) derivatives were synthesized and characterized. The photophysical properties, solvatochromism, ?uorescence decays and electrochemical behaviours were discussed. All luminophores showed very high selectivity towards picric acid (PA) among all other nitroaromatics. All synthesized TPI luminophores showing good selectivity and high sensitivity, not only can detect PA in solution but can also be used in the contact mode for PA in thin-layer chromatography plates. The sensing mechanism was carefully studied by using nuclear magnetic resonance and density functional theory (DFT) studies. The optimal geometries and singlettriplet levels were calculated theoretically by using DFT and time-dependent DFT methods. Furthermore, examinations were carried out to know the optical, electronic, charge transport and stability properties of TPI derivatives as emissive and charge transport materials for organic light-emitting devices (OLEDs). Furthermore, all the TPI derivatives were used as emissive component for fabrication of OLED devices (I and II types) with multilayer con?guration via solution process. The device con?gurations are ITO/PEDOT:PSS/CBP:TPI-1, TPI-2, TPI-3 and TPA-4/TPBi/LiF/Al and ITO/PEDOT:PSS/TPI-1, TPI-2, TPI-3 and TPA-4/TPBi/LiF/Al for doped (device II) and non-doped (device I) devices, respectively. Compared with all, the luminophores containing non-?uorinated linker (CH3-phenyl) showed deep-blue electroluminescence (Commission International de L'Eclairage [CIE], x ? 0.20, y ? 0.17), whereas the ?uorinated linker (CF3-phenyl) containing luminophores exhibited bright-blue emission (CIE, x ? 0.23, y ? 0.21) with 1.4% external quantum ef?ciency.
关键词： Organic light emitting diodes,Sensing,DFT and TD-DFT,Lifetime
更新于2025-09-12 10:27:22
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LED applications in greenhouse and indoor production of horticultural crops
摘要： Arrays of light-emitting diodes (LEDs) are increasingly being used in controlled environments to deliver photoperiodic, supplemental, and sole-source lighting to speciality crops. Compared to conventional light fixtures such as high-pressure sodium or fluorescent, LEDs emitting different bands of radiation can be combined to create light spectra that regulate specific plant responses such as extension growth and flowering. LED applications in horticulture can be divided into three major categories: 1) low-intensity lighting to regulate photoperiodic and photomorphogenic responses; 2) supplemental (photosynthetic) lighting in greenhouses to increase growth and yields; and 3) sole-source lighting to consistently produce crops indoors, conceivably with value-added attributes. Potential advantages of LED lighting include greater efficacy at converting electricity into photosynthetic photons; selection and manipulation of the radiation spectrum to elicit specific plant responses; less emission of radiant heat; more focused lighting, resulting in less loss to non-target areas; instant on/off and dimming capabilities; and greater longevity. The primary barrier to commercial implementation of LED lighting in horticulture continues to be return on investment, which is situational. This paper presents a science-based, practical summary of LED applications in the production of horticultural crops grown in controlled environments, especially vegetable and floriculture crops.
关键词： photoperiodic lighting,sole-source lighting,plant growth,flowering,controlled environments,supplemental lighting,light-emitting diodes
更新于2025-09-12 10:27:22
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Violet/deep-blue fluorescent organic light-emitting diode based on high-efficiency novel carbazole derivative with large torsion angle
摘要： A novel and highly efficient violet/deep-blue fluorescent carbazole and naphthalene-based compound (1) is designed and synthesized. The compound shows intensive violet/deep-blue fluorescence, high photoluminescence efficiency (0.72 in CH2Cl2, 0.65 in film) and narrow full width at half maximum (48 nm). The large torsion angles between carbazole and naphthalene guarantee the weak intermolecular interactions and suppress the π-π interactions in solid state, resulting in the highly efficient violet/deep-blue fluorescence. The maximum emission peak, luminance and external quantum efficiency for violet/deep-blue electroluminescence are 410 nm, 1326 cd/m2 and ～2%, respectively.
关键词： Carbazole,Naphthalene,Violet/deep-blue fluorescence,Organic light-emitting diodes
更新于2025-09-12 10:27:22
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Efficient sky-blue perovskite light-emitting diodes via photoluminescence enhancement
摘要： The efficiencies of green and red perovskite light-emitting diodes (PeLEDs) have been increased close to their theoretical upper limit, while the efficiency of blue PeLEDs is lagging far behind. Here we report enhancing the efficiency of sky-blue PeLEDs by overcoming a major hurdle of low photoluminescence quantum efficiency in wide-bandgap perovskites. Blending phenylethylammonium chloride into cesium lead halide perovskites yields a mixture of two-dimensional and three-dimensional perovskites, which enhances photoluminescence quantum efficiency from 1.1% to 19.8%. Adding yttrium (III) chloride into the mixture further enhances photoluminescence quantum efficiency to 49.7%. Yttrium is found to incorporate into the three-dimensional perovskite grain, while it is still rich at grain boundaries and surfaces. The yttrium on grain surface increases the bandgap of grain shell, which confines the charge carriers inside grains for efficient radiative recombination. Record efficiencies of 11.0% and 4.8% were obtained in sky-blue and blue PeLEDs, respectively.
关键词： radiative recombination,perovskite light-emitting diodes,yttrium (III) chloride,photoluminescence quantum efficiency,wide-bandgap perovskites
更新于2025-09-12 10:27:22
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White Light-Emitting Diodes With Ultrahigh Color Rendering Index by Red/Green Phosphor Layer Configuration Structure
摘要： Currently, white light-emitting diodes (WLEDs) have been widely applied in lighting, display, and medical fields. However, there still exists the problem of low color rendering index (CRI, Ra). In this work, phosphor-converted WLEDs (pc-WLEDs) with ultrahigh Ra were fabricated using Y3Al3Ga2O12:Ce3+ green phosphor and CaAlSiN3:Eu2+ red phosphor configuration structure. The broad emission spectrum of the green phosphor compensates for the gap of the cyan-emitting region that realizes full-spectrum white-light emission. The weight ratio of green/red phosphors was controlled to optimize the optical performances of pc-WLEDs. At the ratio of 0.15/0.012, the fabricated pc-WLED exhibits a natural white light with an ultrahigh Ra of 95.2 and an incredibly small International Commission on Illumination (CIE) chromaticity coordinates deviation (Duv = ?0.0034) at 350 mA. The corresponding correlated color temperature (CCT) and luminous efficiency (LE) are 4526 K and 62.34 lm/W, respectively. Furthermore, two separated phosphor configuration structures were constructed for pc-WLEDs. The R up/G down structure achieves the highest LE of 64.93 lm/W, and the corresponding CCT and Ra are 5714 K and 95.8, respectively, chiefly due to the compensation for reabsorption effect caused by the large difference in the luminous efficacy of radiation (LER) between dichromatic phosphors. The results demonstrate that by adjusting the phosphor configuration structure, the pc-WLEDs with high color rendering can be obtained, which have great applications in high-quality lighting.
关键词： white light-emitting diodes (WLEDs),High color rendering,separated phosphor layer,phosphor configuration
更新于2025-09-12 10:27:22