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991.
着重对比了在以DCM掺杂Alq3为发光层的红光器件的发光区插入超薄LiF层后器件性能的改善。插入超薄LiF层后,器件的最大工作电流密度为487 mA/cm2,相应的最大电致发光亮度为76 740 cd/m2,最大外量子效率为5.9%。器件内量子效率为40%,超过了基于有机荧光小分子发光材料的有机电致发光器件的内量子效率的理论极限值25%。对器件内单线态及三线态激子的形成过程进行了分析,并推测:超薄LiF层的插入提高了器件内单线态电荷转移态/三线态电荷转移态的形成比例,进而提高了器件内单线态激子在激子总数中的比例,最终提高了器件的内量子效率。同时,超薄LiF层的插入改变了发光层内局域的内部电场,使器件的外量子效率不仅没有随电流密度的增加而降低,反而非线性增加。 相似文献
992.
发光二极管(LED)中载流子的输运及复合决定了其非均匀的内热源强度及分布,而芯片温度又影响载流子的输运及复合,两者具有强烈的耦合关系。本文利用非等温多物理场耦合模型对以蓝宝石、Si及SiC为衬底的 LED芯片的内量子效率、光谱特性及光电转换效率进行了系统研究。结果表明:以SiC为衬底的LED芯片具有最小的效率下垂效应(Efficiency droop)及最高的光谱强度和光电转换效率。这是因为与其他两种衬底的LED芯片相比,以SiC为衬底的LED芯片具有最好的散热性能,因此非均匀温度场对其载流子输运及复合的影响最小,使得活性区中的载流子浓度显著增强,漏电流明显下降。 相似文献
993.
A novel transformer-type variable inductor is proposed to achieve a wide tuning range at frequencies as high as K band. The variable inductor is designed, and an intuitive model is built to analyze its performance by HFSS. A lot of mathematical analysis is done in detail. A VCO using the proposed variable inductor is designed with TSMC 0.13 μm CMOS technology for verification. The frequency tuning range of the VCO depends on the proposed variable inductor. The phase noise of the VCO depends on the quality of the LC tank (including the proposed variable inductor and varactors). So a specific AMOS varactor is implemented to improve its quality factor. The VCO is simulated at three typical TSMC fabrication comers (TT, FF, SS) to predict its measure results. The post simulation results shows that the VCO achieves a 20-25.5 GHz continuous tuning range. Its phase noise results at 1 MHz offset are -108.4 dBc/Hz and -100.5 dBc/Hz respectively at the tuning frequencies of 19.6 GHz and 25.5 GHz. The VCO draws only 3 to 6 mA from a 1.2 V power supply. 相似文献
994.
Jonghee Lee Hyunsu Cho Tae-Wook Koh Simone Hofmann Yong Hyun Kim Changhun Yun Tobias Schwab Sebastian Reineke Björn Lüssem Jeong-Ik Lee Seunghyup Yoo Karl Leo Malte C. Gather 《Organic Electronics》2013,14(10):2444-2450
We investigated the control of micro-cavity (MC) effects in organic light-emitting diodes (OLEDs) with the introduction of a striped thin metal layer between the indium tin oxide (ITO) layer and the hole transporting layer (HTL). With an enhanced MC effect obtained through the inserted metal layer, the forward emission of the OLED became stronger and the angular distribution became more forward-directed, leading to a current efficiency (CE) that was nearly 1.45 times higher than that of the reference device without the inserted metal layer. The net CE of the OLEDs with a striped metal layer was found to be determined by the area-weighted average of the CE’s of full-cavity-enhanced OLEDs and non-cavity OLEDs. It was also observed that the trade-off between resonance enhancement in efficiency and angle-dependent color stability, often found problematic in MC-based OLEDs, could be mitigated in a straight-forward manner by changing the relative portion of the metal-covered area. 相似文献
995.
Jungeun Park Hankook Oh Sihyun Oh Jinho Kim Hyun Jin Park Oh Young Kim Jun Yeob Lee Youngjin Kang 《Organic Electronics》2013,14(12):3228-3233
Highly efficient deep blue phosphorescent organic light-emitting diodes (PHOLEDs) using two heteroleptic iridium compounds, (dfpypy)2Ir(acac) and (dfpypy)2Ir(dpm), as a dopant and 9-(3-(9H-carbazol-9-yl)phenyl)-9H-carbazol-3-yl)diphenylphosphine oxide as a host material have been developed. The electroluminescent device of (dfpypy)2Ir(dpm) at the doping level of 3 wt% shows the best performance with external quantum efficiency of 18.5–20.4% at the brightness of 100–1000 cd/m2 and the color coordinate of (0.14, 0.18) at 1000 cd/m2. 相似文献
996.
Zhensong Zhang Pingrui yan Shouzhen Yue Guohua Xie Yu Chen Qingyang Wu Dalong Qu Yi Zhao Shiyong Liu 《Organic Electronics》2013,14(6):1452-1457
It is challenging to obtain broadband emission covering as much of the visible light spectrum as possible in top-emitting white organic light-emitting diodes (TEWOLEDs) due to the well known microcavity effects. In this work, we achieved TEWOLED with three separate peak and negligible angular dependence by employing a high transmittance stack cathode Al (2 nm)/Cu (18)/TcTa (60 nm). The TEWOLED shows an efficiency of 25.6 cd/A, 20.1 Lm/W at 1000 cd/m2, and low voltage of 4.2 V for 1222 cd/m2. Synchronously, we achieved transparent white organic light-emitting diode (TWOLED) using this high transmittance stack cathode, the TWOLED exhibits similar spectrum and comparable luminance from both sides, and the maximum total efficiencies of the TWOLED are 28.6 cd/A, 24.9 Lm/W. 相似文献
997.
Abstract A novel method for designing a beam-switching antenna with the plane dipole is presented. The antenna is composed of double dipoles placed at the center of an active square structure that is divided in four equal sectors by metallic sheets. Metallic patches at the outside of the structure are used to enhance the radiation performance of the antenna. In each step, the diodes in one sector are on, whereas other diodes are off. The sector with off-state diodes defines the direction of the radiation pattern. An antenna model is designed on the substrate of FR4. The proposed antenna operates from 4.8 GHz to 5.5 GHz with gain of 6.3 dBi and F/B (front to back ratio) of 13.2 dBi when the operating frequency is 5.2 GHz. The antenna radiation pattern can be swept in the entire azimuth plane in four steps with a 3 dB beamwidth of 90%. The results reveal that the antenna could be used in the base station of the wireless communication systems. 相似文献
998.
Sunghun Lee Kwon‐Hyeon Kim Daniel Limbach Young‐Seo Park Jang‐Joo Kim 《Advanced functional materials》2013,23(33):4105-4110
An exciplex forming co‐host is introduced in order to fabricate orange organic light‐emitting diodes (OLEDs) with high efficiency, low driving voltage and an extremely low efficiency roll‐off, by the co‐doping of green and red emitting phosphorescence dyes in the host. The orange OLEDs achieves a low turn‐on voltage of 2.4 V, which is equivalent to the triplet energy gap of the phosphorescent‐green emitting dopant, and a very high external quantum efficiency (EQE) of 25.0%. Moreover, the OLEDs show low efficiency roll‐off with an EQE of over 21% at 10 000 cdm?2. The device displays a very good orange color (CIE of (0.501, 0.478) at 1000 cdm?2) with very little color shift with increasing luminance. The transient electroluminescence of the OLEDs indicate that both energy transfer and direct charge trapping takes place in the devices. 相似文献
999.
β‐AgVO3, as a stable phase and a typical silver vanadium oxide, has performed special ionic and electrical properties. The construction of nanoelectronic devices based on ultralong β‐AgVO3 nanoribbons (NRs) is reported, including nano‐field‐effect transistor (nano‐FET) and nano‐Schottky barrier diode (nano‐SBD). Owing to the specific channel structure and ion conductivity, the nano‐FET exhibits typical p‐type semiconductor characteristics and the nano‐SBD with Al contacts performs a prominent rectifying behavior with an on/off ratio of up to 103. Besides, tunable electrical transport properties can be achieved by tailoring the material properties, and it is demonstrated that the bridging NR numbers and diameters have a positive effect on electrical transport properties, while a complex variation trend is observed in the case of surface modification by photo‐irradiation. Electron spin resonance (ESR) spectrum further illuminates that the induced vacancies play an important role on the electrical transport properties of β‐AgVO3 nanoribbons. Easy access to the ultralong β‐AgVO3 NRs makes them a promising candidate for potential applications in nanoelectronic devices. 相似文献
1000.
Sunghun Lee Kwon‐Hyeon Kim Daniel Limbach Young‐Seo Park Jang‐Joo Kim 《Advanced functional materials》2013,23(33):4061-4061