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Purine-based thermally activated delayed fluorescence emitters for efficient organic light-emitting diodes
摘要： Organic fluorescent materials possessing thermally activated delayed fluorescence (TADF) characteristics have attracted tremendous attention. Herein, two TADF emitters (1PXZP and 2PXZP) based on a novel biological base acceptor of 9-methylpurine and commonly used donor of phenoxazine (PXZ) have been successfully synthesized and characterized. Both target compounds possess nearly orthogonal configurations to reduce singlet-triplet splitting energy (ΔEST) for remarkable TADF character. The two emitters show good photoluminescence quantum yields (PLQYs), and thus the organic light-emitting diodes employing 1PXZP and 2PXZP as emitters display good performance with maximum external quantum efficiencies of 10.6% and 13.8%, respectively. The efficiencies of 1PXZP based device show nearly no roll-off at 100 cd m-2 luminance due to the short delayed lifetime (τd) of 3.2 μs. This work manifests that the biological base is a promising acceptor for designing TADF materials.
关键词： Thermally activated delayed fluorescence,organic light-emitting diode,aggregation-induced emission,purine
更新于2025-09-23 15:21:01
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Reference Module in Chemistry, Molecular Sciences and Chemical Engineering || SPECTROPHOTOMETRY/Diode Array ☆
摘要： Diode array spectrometry represents a particular approach for characterizing the result of the interaction between electromagnetic radiation and the sample, based on simultaneous measurement of light intensity over small spectral intervals having equal width. This is achieved through the following sequential stages, as schematically shown in Figs. 1 and 2D: a. interaction between the polychromatic beam and the sample; b. spatial dispersion of the transmitted (eventually reflected or emitted) radiation according to wavelength on multiple channels of equal widths, by means of a fixed optical element; c. imaging the dispersed radiation in a focal plane; and d. (quasi)simultaneous sampling of the dispersed radiation interval using photosensitive detectors, precisely positioned in the focal plane.
关键词： photodiode principle,Diode array spectrometry,concave diffraction gratings,spectrophotometry,instrumentation
更新于2025-09-23 15:21:01
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Lasers in Transurethral Enucleation of the Prostatea??Do We Really Need Them
摘要： The acronym EEP, coding for transurethral Endoscopic Enucleation of the Prostate, was introduced in 2016 by the European Association of Urology (EAU) guidelines panel on management of non-neurogenic male lower urinary tract symptoms (LUTS) and benign prostatic obstruction (BPO). Since then, a laser-based treatment, Holmium Laser Enucleation of the Prostate (HoLEP), and the current-based treatment of bipolar enucleation of the prostate (BipoLEP) are equally appreciated as valuable options for the management of benign prostatic obstruction (BPO). This was mainly inspired by the results of two meta-analyses on randomized controlled trials, comparing open prostatectomy with either Holmium Laser Enucleation of the Prostate (HoLEP) or bipolar enucleation of the prostate (BipoLEP). Prior to that, HoLEP was embraced as the only valid option for transurethral enucleation, although evidence for equivalence existed as early as 2006, but was not recognized due to a plethora of acronyms for bipolar energy-based treatments and practiced HoLEP-centrism. On the other hand, the academic discourse focused on different (other) laser approaches that came up, led by Thulium:Yttrium-Aluminum-Garnet (Tm:YAG) Vapoenucleation (ThuVEP) in 2009 and, finally, transurethral anatomical enucleation with Tm:YAG support (thulium laser enucleation of the prostate, ThuLEP) in 2010. Initially, the discourse on lasers focused on the different properties of lasers rather than technique or surgical anatomy, respectively. In and after 2016, the discussion ultimately moved towards surgical technique and accepting anatomical preparation as the common of all EEP techniques (AEEP). Since then, the unspoken question has been raised, whether lasers are still necessary to perform EEP in light of existing evidence, given the total cost of ownership (TCO) for these generators. This article weighs the current evidence and comes to the conclusion that no evidence of superiority of one modality over another exists with regard to any endpoint. Therefore, in the sense of critical importance, AEEP can be safely and effectively performed without laser technologies and without compromise.
关键词： AEEP,Holmium,LBO,EEP,GreenLEP,Thulium,ThuLEP,Greenlight,Vapoenucleation,ThuVEP,laser,HoLEP,diode
更新于2025-09-23 15:21:01
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Reducing stimulated emission threshold power density of AlGaN/AlN multiple quantum wells by nano-trench-patterned AlN template
摘要： We investigate the crystal quality of epitaxy lateral overgrowth (ELOG) AlN layers and the performance of optical pumping AlGaN-based deep-ultraviolet (DUV) laser diodes (LDs) on two different patterned AlN templates upon sapphire substrate. The full width at half maximum values of (0002) and (10 1(cid:2)2) X-ray diffraction rocking curves of the ELOG AlN layer on the nano-net-patterned AlN template are 76 and 306 arcsec, and the values of that on the nano-trench-patterned AlN template are 114 and 357 arcsec, respectively. Nevertheless, the threshold power density (Pth) of the 272-nm lasing from the multiple quantum wells (MQWs) on the nano-trench-patterned AlN template is 11% lower than that on the nano-net-patterned AlN template. The reason is that the continuous low threading dislocation density (TDD) MQWs zones above the ELOG coalescent areas upon trenched patterns are in parallel with the stimulated light emission direction. When light resonates through the continuous low TDD MQWs zones, it has higher optical gain and less non-radiative recombination than the case on the nano-net-patterned AlN template where the low TDD MQWs zones are discontinuous on the light path. The results indicate that not only the crystal quality but also the TDD distribution originated from the ELOG on the patterned templates have crucial influence on the Pth, and trench-patterned template can improve the performance of waveguide LDs with Fabry-Perot cavities.
关键词： laser diode,deep ultraviolet,multiple quantum wells,AlGaN,AlN
更新于2025-09-23 15:21:01
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A High-Power-Factor Dimmable LED Driver with Integrated Boost Converter and Half-Bridge-Topology Converter
摘要： This paper proposes a dimmable light-emitting diode (LED) driver featuring a high power factor and zero-voltage switching on (ZVS). The circuit is obtained by integrating a boost converter and a dc-dc converter with half-bridge topology. The high power factor is achieved by operating the boost converter in discontinuous current mode (DCM). The LEDs are dimmed by the control scheme of asymmetrical pulse-width modulation (ASPWM). The developed circuit eliminates the inherited dc-o?set current of the transformer in a conventional asymmetrical half-bridge converter by introducing a balance capacitor. Both active switches can operate at ZVS by freewheeling the boost inductor current and the transformer magnetizing current to discharge the energy stored in their parasitic capacitance. The circuit operation is analyzed in detailed, and mathematical equations are derived. Finally, a 115-W prototype circuit for driving high brightness LEDs was built and tested. The experimental results verify the feasibility of the proposed LED driver with satisfactory performance. It can achieve a high power factor and ZVS operation.
关键词： power-factor correction,half-bridge converter,zero-voltage switching on (ZVS),asymmetrical pulse-width modulation (ASPWM),light-emitting diode (LED)
更新于2025-09-23 15:21:01
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Calcium-tributylphosphine oxide passivation enables the efficiency of pure-blue perovskite light-emitting diode up to 3.3%
摘要： Metal halide perovskites are attractive for light-emitting diodes due to their superior optoelectronic properties such as tunable bandgaps, high photoluminescence quantum yields (PLQYs), high color purities and solution processability. In the past several years, impressive progress has been made in perovskite light-emitting diodes (PeLEDs) via microstructure engineering, charge balancing, surface defect passivation, metal ion doping and dimensional engineering. As such, the green, red and near-infrared PeLEDs have achieved impressive external quantum efficiencies (EQEs) exceeding 20%. However, the performances of pure-blue PeLEDs, i.e., brightness and EQEs, still lag largely behind those of the green and red counterparts, which severely impedes the PeLED application in full-color display and solid-state lighting.
关键词： passivation,pure-blue,perovskite,calcium-tributylphosphine oxide,light-emitting diode
更新于2025-09-23 15:21:01
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Physiological responses of pepper seedlings to various ratios of blue, green, and red light using LED lamps
摘要： Chlorophyll absorbs green light less e?ciently than it absorbs other wavelengths in the visible spectrum so green light drives photosynthesis less e?caciously. Green light emitting diodes (LEDs) are also less e?cacious at converting electrical energy into photons than their red and blue counterparts. Consequently, most photosynthetic LED lighting has been designed without including green wavelengths in the spectrum. Plant physiological research has largely focused on light signal responses to red, far-red and blue light, but recent e?orts suggest other wavebands may play an important role in plant development and photosynthetic activity. We have examined the role of monochromatic red, blue and green light and combinations of these colors with regard to seedling growth of bell pepper. The shoots of pepper plants grown under monochromatic green light had greater leaf area and lower speci?c leaf weight (mg cm?2) than those grown under monochromatic blue or red light. Green light also resulted in taller plants with greater dry weight and thicker stems relative to plants grown with blue light. A broad spectrum including red, green, and blue wavelengths resulted in the highest shoot dry weight and plant compactness.
关键词： Plant physiology,Green light,Blue light,Capsicum annuum,Red light,Light emitting diode
更新于2025-09-23 15:21:01
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A Switchable Diplexer Using Switchable Impedance Matching Circuit Technique
摘要： A new type of switchable diplexer is proposed by using switchable impedance matching circuit (SIMC) to connect two quasi-elliptic bandpass filters. The proposed SIMC consists of two different T-network phase shifters to provide the desired impedance matching and a pair of series-parallel configuration p-i-n diode switches to switch the channels on/off. The designed switchable diplexers have four available operation states, so that they realize multiple functional blocks in a single module. The fabricated switchable diplexer features compact size, wide passband, high isolation and independently switchable operation states.
关键词： Bandpass filter,p–i–n diode,switchable,Phase shifter,Diplexer
更新于2025-09-23 15:21:01
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Lens-less PSD measurement of flexible link deflection
摘要： Accurate measurement of change in tip position and orientation of flexible links is of substantial importance for flexible robot control applications. In this paper, a measurement system is proposed to measure the change in position and orientation at the tip of a link subjected to bending and torsion with the use of PSD (Position Sensitive Detector) sensors for space applications. Contrary to existing methods on measuring the spatial deflection of a flexible robot, the proposed method eliminates the requirement of a fragile lens or prism to obtain the angular displacement when PSD sensors are used. Experimental results for measuring five variables are presented for a cantilever flexible link when subjected to bending and torsion under a static load, thereby demonstrating the effectiveness of the proposed method.
关键词： Optical Measurement,Position Sensitive Detector,Flexible Robotic Link,Laser Diode
更新于2025-09-23 15:21:01
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Impact of design and process variation on the fabrication of SiC diodes
摘要： We have studied the influence of design and process variations on the electrical performance of SiC Schottky diodes. On the design side, two design variations are used in the active cell of the diode (segment design and stripe design). In addition, there are two more design variations employed for the edge termination layout of the diodes, namely, field limiting ring (FLR) and junction termination extension (JTE). On the process side, some diodes have gone through an N2O annealing step. The segment design resulted in a lower forward voltage drop (VF) in the diodes and the FLR design turned out to be a better choice for blocking voltages, in the reverse bias. Also, N2O annealing has shown a detrimental effect on the diodes’ blocking performance, which have JTE as their termination design. It degrades the blocking capability of the diodes significantly.
关键词： JBS diode,IGBT,N2O annealing,hybrid SiC,SiC
更新于2025-09-23 15:21:01