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Energy-band alignment and charge balance of electron transport layer with quinary Zn-Mg-Ga-Cl-O nanoparticles in InP-based quantum dot light emitting diodes
摘要： Quinary Zn-Mg-Ga-Cl-O nanoparticles were synthesized for the electron transport layer (ETL) of green InP-based quantum dot light emitting diodes (QLEDs) to achieve band alignment and charge balance. These nanoparticles were synthesized by simple hydrolysis reactions in the solution phase. The band gap of Zn-Mg-Ga-Cl-O increased to 3.85 eV, which exceeded that of ZnO by 0.3 eV. The energy gap between the conduction bands of Zn-Mg-Ga-Cl-O and InP-based quantum dots changed from 0.78 eV to ?0.17 eV. Electron transport in green InP-based QLEDs was reduced, and the charge balance was improved by Zn-Mg-Ga-Cl-O compared with that by ZnO and Zn-Mg-O. Green InP-based QLEDs with a Zn-Mg-Ga-Cl-O ETL exhibited a maximum luminance of 3270 cd/m2. The maximum external quantum efficiency (EQE) and power efficiency of the QLEDs with a Zn-Mg-Ga-Cl-O ETL were 3.8% and 19.6 lm/W, respectively, which were 9.5 times and 9.24 times higher than those of the QLEDs with a ZnO ETL. The maximum EQE and power efficiency were achieved at 2.5 V and 170 cd/m2.
关键词： electron transport layer,InP,light emitting diodes,Quantum dots
更新于2025-09-19 17:13:59
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Spectral Tuning of Efficient CsPbBrxCl3-x Blue Light-Emitting Diodes via Halogen Exchange Triggered by Benzenesulfonates
摘要： CsPbX3 nanocrystals (NCs)-based blue perovskite light-emitting diodes (PeLEDs) are still in a backward position while the green and red counterparts have achieved significant progress in the past few years. The emission spectrum of perovskite NCs can be manipulated via the ratio control of halides in precursor or halogen exchange of NCs. Herein, CsPbBrxCl3-x NCs are synthesized in ambient condition. With tetrabutylammonium p-toluenesulfonate (TBSA) added as the ligand during the purification process of as-synthesized perovskite NCs, bromine in NCs is substituted by chlorine and the spectrum undergoes a blue-shift, whereas chlorine is exchanged by bromine in NCs and the spectrum undergoes a red-shift by introducing sodium dodecylbenzenesulfonate (SDSA) as the ligand. The origin for halogen exchange can be attributed to the synergistic effects of anion and cation of benzenesulfonates. The photoluminescence quantum yield (PLQY) of NCs increases from 7% to 81% due to the effective passivating effects of the strong ionic sulfonate heads, and the blue PeLEDs prepared by this method show a promising external quantum efficiency (EQE) of 2.6%. Our work provides a new approach into spectral tuning of efficient blue PeLEDs.
关键词： halogen exchange,spectral tuning,blue perovskite light-emitting diodes,benzenesulfonates,CsPbX3 nanocrystals
更新于2025-09-19 17:13:59
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Spectrally Tunable and Stable Electroluminescence Enabled by Rubidium Doping of CsPbBr <sub/>3</sub> Nanocrystals
摘要： Perovskite nanocrystals exhibit high photoluminescence quantum yields (PLQYs) and tunable bandgaps from ultraviolet to infrared. However, blue perovskite light-emitting diodes (LEDs) suffer from color instability under applied bias. Developing narrow-bandwidth deep-blue emitters will maximize the color gamut of display technologies. Mixed anion approaches suffer from halide segregation that leads to their spectral instability. Here instead, a mixed cation strategy is employed whereby Rb+ is directly incorporated during synthesis into CsPbBr3 nanocrystals. Blue-emitting perovskite quantum dots (QDs) with stable photoluminescence, PLQYs greater than 60%, tunable emission from 460 to 500 nm, and narrow emission linewidths (<25 nm) are reported. The strategy retains a pure bromine crystal structure resulting in color-pure stable electroluminescence at operating voltages of up to 10 V, peak external quantum efficiencies (EQEs) of 0.87% and 0.11% for sky-blue (490 nm), and deep-blue (464 nm) devices. The sky-blue devices exhibit the highest combined luminance of 93 cd m?2 at an EQE of 0.75%, the best reported to date of perovskite QD LEDs.
关键词： perovskite quantum dots,LEDs,light-emitting diodes,halide perovskites,blue emission
更新于2025-09-19 17:13:59
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Chlorine Vacancy Passivation in Mixed Halide Perovskite Quantum Dots by Organic Pseudohalides Enables Efficient Rec. 2020 Blue Light-Emitting Diodes
摘要： Blue-emitting perovskites are easily attainable by precisely tuning the halide ratio of mixed halide (Br/Cl) perovskites (MHPs). However, the adjustable halide ratio also hinders the passivation of Cl vacancies – the main source of trap states leading to inferior performance blue MHP light-emitting diodes (LEDs). Here, we report a strategy to passivate Cl vacancies in MHP quantum dots (QDs) using non-polar-solvent-soluble organic pseudohalide (n-dodecylammonium thiocyanate (DAT)), enabling blue MHP LEDs with greatly enhanced efficiency. Density-functional-theory calculations reveal that the thiocyanate (SCN-) groups fill in the Cl vacancies and remove electron traps within the bandgap. DAT-treated CsPb(BrxCl1-x)3 QDs exhibit near unity (~100%) photoluminescence quantum yields; and their blue (~470 nm) LEDs are spectrally stable with an external quantum efficiency (EQE) of 6.3% – a record for perovskite LEDs emitting in the 460-480 nm range relevant to Rec. 2020 display standards – and a half-lifetime of ~99 s.
关键词： light-emitting diodes,organic pseudohalides,blue emission,perovskite,chlorine vacancy passivation,quantum dots
更新于2025-09-19 17:13:59
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An efficient full‐bridge resonant converter for light emitting diode (LED) application with simple current control
摘要： New power control is introduced in the full‐bridge dc‐dc converter to drive an LED lamp in this paper. LEDs are semiconductor devices that behave like a constant voltage load with low equivalent series resistance (ESR). Hence, they require precise control for current regulation. In the proposed driver, the LED lamp is driven by two voltage sources connected in series through a series resonant circuit. It processes the majority of lamp power through the full‐bridge diode rectifier and supplies small power through a center‐tapped rectifier. The LED lamp current is controlled at the selected operating current by using center‐tapped rectifier output voltage. In addition, pulse‐width modulation (PWM) dimming is implemented. The proposed topology features zero‐voltage switching (ZVS), regulation of lamp current, dimming operation, and high efficiency. The working principle, performance, and prototype validation are given for the proposed LED driver.
关键词： DC‐DC resonant converters,light emitting diodes,driver circuits
更新于2025-09-19 17:13:59
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23.4: <i>Invited Paper:</i> The Longevity Study for Hybrid Colloidal Quantum Dot Optoelectronic Devices
摘要： The nano-scale size of colloidal quantum dots provide unique properties, such as strong luminescent efficiency, wavelength tunable emission, and narrow linewidth etc., which are desirable for high quality display devices. However, the reliability of these nanoparticles is always the center of attention when the commercialization issue is discussed. In this paper, we will review our latest result on the hybrid package method that can dramatically these magnificent optoelectronic materials . lifetime of improve the
关键词： reliability tests,Light emitting diodes,colloidal quantum dots,solar cells
更新于2025-09-19 17:13:59
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24.2: <i>Invited Paper:</i> High‐resolution OLED Display Fabricated by Electrohydrodynamic Printing Method
摘要： A high resolution OLED display was fabricated by using electrohydrodynamic printing method. The printed inks were poly(dibenzothiophene-S, S-dioxide-co-9,9-dioctyl-2,7-fluorene) (PPF-SO). Both of the printer operation voltage and the solvent properties dominated the ink’s printability and printing stability. Line widths of the printed polymers could be controlled. A mono-color display with resolution over 2000 PPI was realized. The electrohydrodynamic printing method for fabrication of OLED displays will be discussed in the presentation.
关键词： High resolution,Organic light-emitting diodes,Solution process,Electrohydrodynamic printing
更新于2025-09-19 17:13:59
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Efficiency Enhancement of Perovskite CsPbBr <sub/>3</sub> Quantum Dot Light-emitting Diodes by Doped Hole Transport Layer
摘要： Balanced charge injection is essential to high-performance Perovskite CsPbBr3 quantum dot-based light-emitting diodes (QLEDs). However, low mobility of hole-transport materials (HTMs) severely restrict improving performance of QLEDs. Herein, we provide a novel HTMs to improve the highest occupied molecular orbital (HOMO) energy level structure and carrier mobility by doping poly (9-vinlycarbazole) (PVK) and poly [N, N′-bis(4-butylphenyl)-N, N′-bis(phenyl) benzi-dine] (poly-TPD). We also introduce poly (methyl methacrylate) (PMMA) as electron block layer to further achieve charge injection balance. Finally, an enhanced external quantum efficiency (EQE) of 0.53% and 414.83 cd/m2 was obtained. Compared with the untreated QLED, this result has been 8-fold enhanced, provides a new approach to attain better performance.
关键词： Quantum Dot Light-emitting Diodes,Efficiency Enhancement,Perovskite CsPbBr3,Hole Transport Layer
更新于2025-09-19 17:13:59
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Synergistic Effects of Charge Transport Engineering and Passivation Enabling Efficient Inverted Perovskite Quantum-dot Light-emitting Diodes
摘要： All inorganic perovskite quantum dots (QDs) have attracted much attention in the optoelectronic devices due to their fascinating properties such as high photoluminescence quantum yields (PLQYs), narrow emission peak, and facile synthesis process. Herein, we report a synergistic strategy of interfacial engineering and passivation. We construct an inverted device structure with Zinc Magnesium Oxide (Zn0.95Mg0.05O) as electron transport layer and p-n charge generation junction of (N,N’-Bis(naphthalen-1-yl)- N,N’- bis(phenyl) benzidine/ 1,4,5,8,9,11-hexaazatriphenylene-hexacarbonitrile) as hole transport layer to facilitate and balance the charge injection/transport. Meanwhile, a facile post-passivation technique is employed to passivate the cesium lead bromide (CsPbBr3) QDs via supplement of Br anion. The treated QDs exhibit improve PLQY due to decreased surface defect sites and enhanced radiative recombination. As a result, our perovskite quantum dot light-emitting diodes (PVQDLEDs) obtain a maximum luminance of 75792 cd m-2, an extremely low turn-on voltage of 1.9 V, and a maximum external quantum efficiency (EQE) of 5.95%, leading to an increase in EQE by 100% compared with that of the control device. Our work offers an effective approach to improve the performance of PVQDLEDs via multiple effects for the application of displays and solid-state lighting.
关键词： perovskite quantum dots,inverted device structure,passivation,light-emitting diodes,charge transport engineering
更新于2025-09-19 17:13:59
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Influence of nonradiative Auger process in the lanthanide complexes lifetime near interfaces in organic light-emitting diode structures
摘要： The low efficiency of organic light-emitting diodes based on lanthanide complexes is generally attributed to the triplet-triplet annihilation processes in the regime of high concentration of excited states caused by their long lifetimes and optical losses near the interfaces of multilayer device structures. Despite the enormous effort to synthesize short-lived complexes and minimize the optical losses in the interfaces, it remains insufficient in understanding the exciton recombination processes that reduce the lifetime of these complexes. Herein, we investigated the influence of the exciton recombination processes on a Tb complex (Tb-C) lifetime in the regime of a highly excited state concentration as a function of the distance between the carrier layer and the interface by using a typical organic light-emitting diode structure. Our results show that a 10 nm-thick Alq3 layer decreases the exciton lifetime of the Tb-C, increasing approximately by 16 times the spontaneous emission decay rate of triplet exciton. The effects of interference and optical losses at the metallic interface contribute actively to the modulation of the emission intensity and lifetime decay. However, these effects alone do not explain the significant increase in the emission decay rate. The nonradiative Auger process at the Alq3/Tb-C interface seems to be largely accountable for the Tb-C lifetime reduction as the energy released by the terbium ion occurs by the excitation of an adjacent electron at higher energy. Furthermore, we propose a simple theoretical model to explain the observed effects. These results can provide a new approach to reduce the lanthanide complexes’ lifetime through the Auger electron process near the interface and thus improve the performance of organic light-emitting diodes.
关键词： exciton recombination,Auger process,organic light-emitting diodes,lifetime reduction,lanthanide complexes
更新于2025-09-19 17:13:59