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1.
金属卤化物钙钛矿材料具有带隙可调、半峰宽窄、载流子迁移率高和荧光量子效率高等特点,在照明和显示领域显示出良好的应用潜力。通过对钙钛矿薄膜组分和器件结构的优化,红光和绿光钙钛矿发光二极管（PeLEDs）的外量子效率均已超过了20%,蓝光钙钛矿材料存在稳定性差、深能级陷阱多和电荷注入困难等问题,限制了蓝光PeLEDs的发展。因此,本文从三维钙钛矿材料、准二维钙钛矿材料和钙钛矿量子点入手,综述了这3种蓝光材料如何通过解决上述问题来提升相应器件的性能,对蓝光PeLEDs面临的机遇和挑战进行了总结和展望。 相似文献
2.
Flexible light-emitting diodes(LEDs)are highly desired for wearable devices,flexible displays,robotics,biomedicine,etc.Traditionally,the transfer process of an ultrathin wafer of about 10–30μm to a flexible substrate is utilized.However,the yield is low,and it is not applicable to thick GaN LED chips with a 100μm sapphire substrate.In this paper,transferable LED chips utilized the mature LED manufacture technique are developed,which possesses the advantage of high yield.The flexible LED array demonstrates good electrical and optical performance. 相似文献
3.
ZHENG Dai-shun ZHANG Xu QIAN Ke-yuan 《光电子．激光》2006,2(1):5-8
为解释发光二极管（LEDs）中的负电容（NC）现象,提出了在有源区与局部强复合效应有关的新模型,首次通过对载流子连续性方程的求解导出了NC的解析表达式。理论结果表明,在一定的范围内激活区载流子复合速率越大,LEDs中的NC效应越显著,这与实验结果完全一致。它表明,LEDs中的NC是由其激活区载流子复合引起的,而非外部原因造成。 相似文献
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Aditya Mishra Masoud Alahbakhshi Ross Haroldson Qing Gu Anvar A. Zakhidov Jason D. Slinker 《Advanced functional materials》2021,31(31):2102006
Blue electroluminescence is highly desired for emerging light-emitting devices for display applications and optoelectronics in general. However, saturated, efficient, and stable blue emission has been challenging to achieve, particularly in mixed-halide perovskites, where intrinsic ion motion and halide segregation compromises spectral purity. Here, CsPbBr3−xClx perovskites, polyelectrolytes, and a salt additive are leveraged to demonstrate pure blue emission from single-layer light-emitting electrochemical cells (LECs). The electrolytes transport the ions from salt additives, enhancing charge injection and stabilizing the inherent perovskite emissive lattice for highly pure and sustained blue emission. Substituting Cl into CsPbBr3 tunes the perovskite luminescence from green through blue. Sky blue and saturated blue devices produce International Commission on Illumination coordinates of (0.105, 0.129) and (0.136, 0.068), respectively, with the latter meeting the US National Television Committee standard for the blue primary. Likewise, maximum luminances of 2900 and 1000 cd m−2, external quantum efficiencies (EQEs) of 4.3% and 3.9%, and luminance half-lives of 5.7 and 4.9 h are obtained for sky blue and saturated blue devices, respectively. Polymer and LiPF6 inclusion increases photoluminescence efficiency, suppresses halide segregation, induces thin-film smoothness and uniformity, and reduces crystallite size. Overall, these devices show superior performance among blue perovskite light-emitting diodes (PeLEDs) and general LECs. 相似文献
6.
近年来,金属卤化物蓝光钙钛矿发光二极管（Perovskitelight-emittingdiodes,PeLEDs）的发展十分迅速。然而,氯/溴混合的蓝光钙钛矿在电场作用下容易发生卤素离子迁移,致使发光光谱发生红移。光谱的不稳定性已严重地阻碍了蓝光PeLEDs的商业应用。本文通过在钙钛矿前驱体中引入三氟乙酸铯（CsTFA）来提高CsPbClBr2晶体的成核密度,诱导形成了小晶粒的钙钛矿发光薄膜,进而增加了钙钛矿薄膜的致密度。更重要的是,CsTFA中的碳氧双键（C=O）可以有效钝化CsPbClBr2晶粒晶界处的缺陷,抑制卤素阴离子发生离子迁移,极大地提升蓝光PeLEDs的光谱稳定性。在10V的电压下,PeLEDs的发光光谱仍可以保持非常稳定。此外,对比参比器件,PeLEDs的最大亮度和最高外量子效率也分别提高了31倍和8倍。 相似文献
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A. Y. Polyakov N. B. Smirnov A. V. Govorkov Jihyun Kim F. Ren G. T. Thaler R. M. Frazier B. P. Gila C. R. Abernathy S. J. Pearton I. A. Buyanova G. Y. Rudko W. M. Chen C. -C. Pan G. -T. Chen J. -I. Chyi J. M. Zavada 《Journal of Electronic Materials》2004,33(3):241-247
Electrical and electroluminescent properties were studied for GaN/InGaN light-emitting diodes (LEDs) with the n-GaN layer
up and with the top portion of the n layer made of undoped GaMnN to allow polarization modulation by applying an external
magnetic field (so-called “spin-LEDs”). The contact annealing temperature was kept to 750°C, which is the thermal stability
limit for retaining room-temperature magnetic ordering in the GaMnN layer. Measurable electroluminescence (EL) was obtained
in these structures at threshold voltages of ∼15 V, with a lower EL signal compared to control LEDs without Mn. This is related
to the existence of two parasitic junctions between the metal and the lower contact p-type layer and between the GaMnN and
the n-GaN in the top contact layer. 相似文献
8.
C. Zhang S. Hoger K. Pakbaz F. Wudl A. J. Heeger 《Journal of Electronic Materials》1994,23(5):453-458
By dispersing an electron transporting molecular dopant into the active semiconducting luminescent polymer, we have achieved
improved efficiencies for green light-emitting diodes (LEDs). These green emitting LEDs were fabricated by adding an electron
transporting molecular dopant, 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-l,3,4-oxadiazole (PBD), into the semiconducting luminescent
polymer as the emitting layer in the polymer LEDs. The devices used poly(2-cholestanoxy-5-thexyldimethylsilyl-l,4-phenylene
vinylene) (CS-PPV), a new soluble green light emitter, as the semiconducting luminescent polymer and either aluminum or indium
as the electron injection electrodes. Quantum efficiencies of LEDs with the electron transporting molecular additive in the
luminescent polymer and an Al electrode are about 0.3% photons per electron, better by a factor of 18 than similar devices
made without the addition of the electron transport molecular dopant; quantum efficiencies of similar LEDs fabricated with
an In electrode are 0.23% photons per electron, better by a factor of 16 than devices without the electron transport molecular
additive. 相似文献
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为了研究图形化蓝宝石衬底(PSS)的结构和形貌对GaN基发光二极管(LED)光学性能的影响,对PSS的制备工艺和参数进 行了调控,从而 形成具有不同填充因子的蒙古包形PSS(HPSS)和金字塔形PSS(TPSS)两种衬底,用于生长 和制备蓝光LED 芯片。通过对TPSS-LED的光学性能测试和分析得到,随着PSS填充因子的增大, LED的 光输出功 率也增大;进而比较具有相同填充因子的HPSS和TPSS的光学性能表明,HPSS明显优于TPSS。 因此, PSS填充因子的增大,能够提高LED的光输出功率;优化PSS的结构可以改善LED中光出射途径 ,从而更有效提高LED的光发射效率。 相似文献
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Colloidal core/shell quantum dots (QDs) are promising for solar technologies because of their excellent optoelectronic properties including tunable light absorption/emission spectra, high photoluminescence quantum yield (PLQY), suppressed Auger recombination, efficient charge separation/transfer, and outstanding photo-/thermal-/chemical stability. In this review, engineered core/shell QDs with various types of band structures and corresponding device performance in luminescent solar concentrators (LSCs), light-emitting diodes (LEDs), solar-driven photoelectrochemical (PEC) devices, and QDs-sensitized solar cells (QDSCs) are summarized. In particular, the applications of interfacial layer engineering and eco-friendly, heavy metal-free core/shell QDs in optoelectronic devices are highlighted. Finally, strategies towards the developments and practical perspectives of core/shell QDs are briefly mentioned to offer guidelines for achieving prospective high-efficiency and long-term stable QD devices. 相似文献
12.
表面粗化提高倒装AlGaInP发光二极管的光提取效率 总被引：1，自引：1，他引：0
对发光二极管进行表面粗化能够大幅度的提高其光提取效率。利用晶片键合技术并采用湿法刻蚀的办法粗化n面AlGaInP表面制作了一种带表面粗化的倒装薄膜发光二极管。刻蚀后的表面形貌呈现金字塔状。270μm x 270μm管芯裸装在TO-18金属管座上,在20mA的注入电流下,粗化了的LED-I光强达到了315mcd,输出光功率达到了4.622mW,比没有粗化的LED-II的光功率高1.7倍。光功率增加的原因在于粗化后形成的这种金字塔状表面,其不但减少了背部镜面系统和半导体-空气接触面的反射,而且能有效的将光从LED中散射出去。 相似文献
13.
Zhenwei Ren Kai Wang Xiao Wei Sun Wallace C. H. Choy 《Advanced functional materials》2021,31(30):2100516
Substantial progress has been made in blue perovskite light-emitting diodes (PeLEDs). In this review, the strategies for high-performance blue PeLEDs are described, and the main focus is on the optimization of the optical and electrical properties of perovskites. In detail, the fundamental device working principles are first elucidated, followed by a systematical discussion of the key issues for achieving high-quality perovskite nanocrystals (NCs) and quasi-2D perovskites. These involve ligand optimization and metal doping in enhancing the carrier transport and reducing the traps of perovskite NCs, as well as the perovskite phase modulation and defect passivation in improving energy transfer and emission efficiency of quasi-2D perovskites. The strategies for efficient 3D mixed-halide perovskite and lead-free perovskite blue LEDs are then briefly introduced. After that, other strategies, including effective charge transport layer, efficient perovskite emission system, and effective device architecture for high light outcoupling efficiency, are further discussed to boost the blue PeLED performances. Meanwhile, the testing standard of blue PeLED lifetime is suggested to enable the direct comparisons of the device operational stability. Finally, challenges and future directions for blue PeLEDs are addressed. 相似文献
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Haibo RAO Kun DING Jirong SONG Likun XIE Wei WANG Xianlong WAN Linsong ZHOU Junyuan LIAO 《中国光电子学前沿》2012,(2)
Phosphor-converted light-emitting diodes (pcLEDs),which employ blue LEDs with yellow phosphors to generate white light illumination,is a widely used solidstate lighting source.In order to conduct a pho... 相似文献
16.
LEDs-DOAS系统的标定及反演方法研究 总被引：3，自引：3，他引：0
针对氙弧灯作为主动差分吸收谱(DOAS)宽带热光源带来严重的能源浪费和一些不必要的干扰,提出采用新型冷光源—发光二极管(LEDs)作为光学遥感DOAS系统的光源。研究了LEDs-DOAS系统的标定及反演方法,首先介绍了LEDs-DOAS光学遥感系统的结构,分析了其获取痕量气体大气浓度的原理;然后通过把具有线状吸收谱特性的汞灯光引入到LEDs-DOAS仪器,得到仪器函数,对系统进行标定;再把标准库待测气体的吸收截面和仪器函数卷积,得到该痕量气体的在LEDs-DOAS仪器吸收强度,并基于最小二乘原理反演痕量气体的大气浓度;最后利用NO2样品标定LEDs-DOAS系统的测量精度,实验结果表明,测量误差小于5%。 相似文献
17.
Currently, the most popular way to manufacture white light-emitting diodes (WLEDs) is based on blue-emitting InGaN LED chips (440–460 nm) and yellow-emitting phosphor coating (520–700 nm) to produce white light lighting. However, because conventional white WLEDs lack the uniformly distributed continuous emission spectrum compared to natural sunlight: “blue overshoot” (extra 440–460 nm blue-light can cause damage to the retina) and “cyan gap” (470–520 nm wavelength range). Here, a novel strategy to “kill two birds with one stone” is reported: using the stable and bright polymer encapsulated perovskite nanocrystals (PNCs) composite films as the cyan color converters that efficiently absorb the “blue overshoot” and effectively emit the cyan light to fill the “cyan gap”. A series of polymer-encapsulated PNC films is achieved that can reach very high photoluminescence quantum yield (PL QY) of 90–95% under 450 nm blue-light excitation. Importantly, both 370 nm UV-excited WLED and 455 nm blue-excited WLED devices are constructed that exhibit smoothly and evenly distributed white light without blue overshoot and cyan gap, which was not achieved before for blue-excited cyan-emissive materials. This study paves the way toward the application of PNC color converters in the next generation full-visible-spectrum WLED lighting that mimic the natural daylight. 相似文献
18.
Yang Shen Hai-Yan Wu Yan-Qing Li Kong-Chao Shen Xingyu Gao Fei Song Jian-Xin Tang 《Advanced functional materials》2021,31(45):2103870
Efficient and stable blue emission of perovskite light-emitting diodes (PeLEDs) is a requisite toward their potential applications in full-color displays and solid-state lighting. Rational manipulation over the entire electroluminescence process is promising to break the efficiency limit of blue PeLEDs. Herein, a facile device architecture is proposed to achieve efficient blue PeLEDs for simultaneously reducing the energetic loss during electron-photon conversion and boosting the light outcoupling. Effective interfacial engineering is employed to manipulate the perovskite crystallization nucleation, enabling highly compact perovskite nanocrystal assemblies and suppressing the trap-induced carrier losses by means of interfacial hydrogen bonding interactions. This strategy contributes to a high external quantum efficiency (EQE) of 12.8% for blue PeLEDs emitting at 486 nm as well as improved operational stability. Moreover, blue PeLEDs reach a peak EQE of 16.8% with the incorporation of internal outcoupling structures for waveguided light, which can be further raised to 27.5% by integrating a lens-based structure for substrate-mode light. These results verify the validity of this strategy in producing efficient and stable blue PeLEDs for practical applications. 相似文献
19.
Metal halide perovskites have attracted considerable attention for light-emitting diode (LED) applications due to their desirable optoelectronic properties including high brightness and color purity. However, the performance of blue perovskite LEDs (PeLEDs) remains inferior to their red and green counterparts. Herein, an ionic liquid (IL), specifically 1-butyl-3-methylimidazolium tetrafluoroborate is introduced as the interlayer on the hole transport layer (HTL). This IL demonstrates a strong interaction with the perovskite emissive layer, resulting in effective defect passivation and a shallower valence band maximum. Consequently, nonradiative recombination is reduced, and hole injection is enhanced. Additionally, a soft lithography method employing a transfer process is successfully developed that enables precise micropatterning of the perovskite light-emitting layer. Through these advancements, the IL-modified PeLED exhibits pure blue emission at 470 nm with a maximum luminance of 891 cd m−2 and an impressive maximum EQE of 8.3%. Furthermore, the micro PeLED with an IL interlayer achieves a maximum luminance of 400 cd m−2 and a maximum EQE of 3.9%. 相似文献