共查询到20条相似文献，搜索用时 46 毫秒
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我们研究了生长温度、TMIn/TEGa和Ⅴ/Ⅲ比对 InGaN/GaN多量子阱表面v型缺陷的影响。当TMIn的流量从180sccm增加到200sccm,v型缺陷的密度也从2.721018/cm2 增加到了5.241018 /cm2, v型缺陷的深度和宽度也随着TMIn流量的增加而增加。当生长温度从748℃增加到758℃, v型缺陷的密度分别是2.05108/cm2, 2.72108/cm2 和 4.23108/cm2,V型缺陷的密度随着生长温度的增加而增加。当NH3的流量从5000sccm增加到8000sccm, v型缺陷的密度分别为 6.341018/cm2, 2.721018/cm2, 4.131018/cm2。我们在753℃, TMIn 流量为180sccm, NH3 流量为6600sccm时,得到了晶体质量最好的InGaN/GaN 多量子阱,表面平整,v型缺陷的密度也比较少。V型缺陷的深度从10nm到30nm,宽度从100nm到200nm,为了抑制v型缺陷对GaN基LEDs反向电流(IR)和静电放电 (ESD) 的影响,我们需要生长更厚的p-GaN来填充这些v型缺陷。 相似文献
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随着氮(N)面GaN材料生长技术的发展,基于N面GaN衬底的高亮度发光二极管(LED)的研究具有重要的科学意义.研究了具有高发光功率的N面GaN基蓝光LED的新型结构设计,通过在N面LED的电子阻挡层和多量子阱有源层之间插入p型InGaN/GaN超晶格来提高有源层中的载流子注入效率.为了对比N面GaN基LED优异的器件性能,同时设计了具有相同结构的Ga面LED.通过对两种LED结构的电致发光特性、有源层中能带图、电场和载流子浓度分布进行比较可以发现,N面LED在输出功率和载流子注入效率上比Ga面LED有明显的提升,从而表明N面GaN基LED具有潜在的应用前景. 相似文献
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生长温度对InGaN/GaN多量子阱LED光学特性的影响 总被引：1，自引：0，他引：1
利用低压MOCVD系统,在蓝宝石衬底上外延生长了InGaN/GaN多量子阱蓝紫光LED结构材料.研究了生长温度对有源层InGaN/GaN多量子阱的合金组分、结晶品质及其发光特性的影响.结果表明当生长温度从730℃升到800℃时,LED的光致发光波长从490nm移到380nm,室温下PL谱发光峰的半高全宽从133meV降到73meV,表明了量子阱结晶性的提高.高温生长时,PL谱中还观察到了GaN的蓝带发光峰,说明量子阱对载流子的限制作用有所减弱.研究表明,通过改变生长温度可以对LED发光波长及有源层InGaN的晶体质量实现良好的控制. 相似文献
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研究了采用MOCVD技术分别在100与500Torr反应室压力下生长的非故意掺杂GaN薄膜的光学与电学性能。研究表明,低压100Torr外延生长条件可以有效地降低Ga与NH3气相反应造成GaN薄膜的碳杂质沾污,从而抑制造成光致发光中黄光峰与蓝光峰的深受主的形成,所制备的材料表现出较好的光学性能。同时,不同生长压力下的GaN薄膜表现出相异的电学性能,即在500Torr下生长的样品通常表现出更高的载流子浓度（（4.6-6.4）×1016 cm-3）与更高的迁移率（446-561cm2/（V.s））,而100Torr下生长的样品通常表现为更低的载流子浓度（1.56-3.99）×1016 cm-3与更低迁移率（22.9-202cm2/（V.s））。 相似文献
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Jwo‐Huei Jou Chun‐Yu Hsieh Jing‐Ru Tseng Shiang‐Hau Peng Yung‐Cheng Jou James H. Hong Shih‐Ming Shen Ming‐Chun Tang Pin‐Chu Chen Chun‐Hao Lin 《Advanced functional materials》2013,23(21):2750-2757
In response to the call for a physiologically‐friendly light at night that shows low color temperature, a candle light‐style organic light emitting diode (OLED) is developed with a color temperature as low as 1900 K, a color rendering index (CRI) as high as 93, and an efficacy at least two times that of incandescent bulbs. In addition, the device has a 80% resemblance in luminance spectrum to that of a candle. Most importantly, the sensationally warm candle light‐style emission is driven by electricity in lieu of the energy‐wasting and greenhouse gas emitting hydrocarbon‐burning candles invented 5000 years ago. This candle light‐style OLED may serve as a safe measure for illumination at night. Moreover, it has a high color rendering index with a decent efficiency. 相似文献
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Lianfeng Zhao Nicholas Rolston Kyung Min Lee Xunhua Zhao Marcos A. Reyes‐Martinez Nhu L. Tran Yao‐Wen Yeh Nan Yao Gregory D. Scholes Yueh‐Lin Loo Annabella Selloni Reinhold H. Dauskardt Barry P. Rand 《Advanced functional materials》2018,28(31)
Perovskite light‐emitting diodes (LEDs) require small grain sizes to spatially confine charge carriers for efficient radiative recombination. As grain size decreases, passivation of surface defects becomes increasingly important. Additionally, polycrystalline perovskite films are highly brittle and mechanically fragile, limiting their practical applications in flexible electronics. In this work, the introduction of properly chosen bulky organo‐ammonium halide additives is shown to be able to improve both optoelectronic and mechanical properties of perovskites, yielding highly efficient, robust, and flexible perovskite LEDs with external quantum efficiency of up to 13% and no degradation after bending for 10 000 cycles at a radius of 2 mm. Furthermore, insight of the improvements regarding molecular structure, size, and polarity at the atomic level is obtained with first‐principles calculations, and design principles are provided to overcome trade‐offs between optoelectronic and mechanical properties, thus increasing the scope for future highly efficient, robust, and flexible perovskite electronic device development. 相似文献
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研究了Ag/p-GaN欧姆接触的工艺,得到较为优化的工艺方法并应用于器件制备。分别采用直接剥离Ag、氧等离子体去底胶后剥离Ag和湿法腐蚀Ag三种工艺制备Ag图形,对比了三种工艺样品的粘附性及接触电性,发现直接剥离Ag工艺存在Ag脱落问题,去底胶后剥离Ag工艺无法形成欧姆接触,而腐蚀后退火的样品则可以实现较好的粘附和较佳电性;通过XPS分析了不同工艺对接触特性影响的机理。进一步,对比优化了Ag蒸发前表面化学处理工艺,结果表明酸性溶液处理或碱性溶液处理可以有效降低欧姆接触电阻率,酸性溶液处理略优。优化后的欧姆接触工艺可应用于可见光及深紫外LED器件制备,器件电学性能如下:在40A/cm2电流密度下,蓝色发光二极管电压为2.95V,紫外发光二极管电压为6.01V。 相似文献
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Elisa Fresta Verónica Fernández‐Luna Pedro B. Coto Rubén D. Costa 《Advanced functional materials》2018,28(24)
Solid‐state lighting (SSL) is one of the biggest achievements of the 20th century. It has completely changed our modern life with respect to general illumination (light‐emitting diodes), flat devices and displays (organic light‐emitting diodes), and small labeling systems (light‐emitting electrochemical cells). Nowadays, it is however mandatory to make a transition toward green, sustainable, and equally performing lighting systems. In this regard, several groups have realized that the actual SSL technologies can easily and efficiently be improved by getting inspiration from how natural systems that manipulate light have been optimized over millennia. In addition, various natural and biocompatible materials with suitable properties for lighting applications have been used to replace expensive and unsustainable components of current lighting devices. Finally, SSL has also started to revolutionize the biomedical field with the achievement of efficient implantable lighting systems. Herein, the‐state‐of‐art of (i) biological materials for lighting devices, (ii) bioinspired concepts for device designs, and (iii) implantable SSL technologies is summarized, highlighting the perspectives of these emerging fields. 相似文献
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无机、有机LED和EL白色发光及绿色照明 总被引：1，自引：0，他引：1
用无机白色ＬＥＤ照明由于不含Ｈｇ,因而无公害,被称为绿色照明。描述了无机ＬＥＤ的特性及进展,特别描述了与发光粉结合成新的白光ＬＥＤ的发展动态;同时还评述了无机白光ＥＬ和有机ＥＬ白光发射在绿色照明应用的可能性。 相似文献
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A study of hybrid light‐emitting diodes (HyLEDs) fabricated with and without solution‐processible Cs2CO3 and Ba(OH)2 inorganic interlayers is presented. The interlayers are deposited between a zinc oxide electron‐injection layer and a fluorescent emissive polymer poly(9‐dioctyl fluorine–alt‐benzothiadiazole) (F8BT) layer, with a thermally evaporated MoO3/Au layer used as top anode contact. In comparison to Cs2CO3, the Ba(OH)2 interlayer shows improved charge carrier balance in bipolar devices and reduced exciton quenching in photoluminance studies at the ZnO/Ba(OH)2/F8BT interface compared to the Cs2CO3 interlayer. A luminance efficiency of ≈28 cd A?1 (external quantum efficiency (EQE) ≈ 9%) is achieved for ≈1.2 μm thick single F8BT layer based HyLEDs. Enhanced out‐coupling with the aid of a hemispherical lens allows further efficiency improvement by a factor of 1.7, increasing the luminance efficiency to ≈47cd A?1, corresponding to an EQE of 15%. The photovoltaic response of these structures is also studied to gain an insight into the effects of interfacial properties on the photoinduced charge generation and back‐recombination, which reveal that Ba(OH)2 acts as better hole blocking layer than the Cs2CO3 interlayer. 相似文献
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K.‐C. Wu P.‐J. Ku C.‐S. Lin H.‐T. Shih F.‐I. Wu M.‐J. Huang J.‐J. Lin I‐C. Chen C.‐H. Cheng 《Advanced functional materials》2008,18(1):67-75
Three blue‐light emitting dipyrenylbenzene derivatives, 1‐(4‐(1‐pyrenyl)phenyl)pyrene (PPP), 1‐(2,5‐dimethoxy‐4‐(1‐pyrenyl)phenyl)pyrene (DOPPP), and 1‐(2,5‐dimethyl‐4‐(1‐pyrenyl)phenyl)pyrene (DMPPP), have been prepared by the Suzuki coupling reaction of aryl dibromides with pyreneboronic acid in high yields. These compounds exhibit high glass‐transition temperatures of 97–137 °C and good film‐forming ability. As revealed from single‐crystal X‐ray analysis, these dipyrenylbenzenes adopt a twisted conformation with inter‐ring torsion angles of 44.5°–63.2° in the solid state. The twisted structure is responsible for the low degree of aggregation in the thin films that leads to fluorescence emission of the neat films at 446–463 nm, which is shorter than that of the typical pyrene excimer emission. The low degree of aggregation is also conducive for the observed high fluorescence quantum yields of 63–75%. In organic light‐emitting diode (OLED) applications, these dipyrenylbenzenes can be used as either the charge transporter or host emitter. The non‐doped blue OLEDs that employ these compounds as the emissive layer can achieve a very high external quantum efficiency (ηext) of 4.3–5.2%. In particular, the most efficient DMPPP‐based device can reach a maximum ηext of 5.2% and a very high luminescence of 40 400 cd m–2 in the deep‐blue region with Commission Internationale d'Énclairage (CIE) coordinates of (0.15, 0.11). 相似文献
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Ming Liu Xiang‐Long Li Dong Cheng Chen Zhongzhi Xie Xinyi Cai Gaozhan Xie Kunkun Liu Jianxin Tang Shi‐Jian Su Yong Cao 《Advanced functional materials》2015,25(32):5190-5198
Two novel naphtho[1,2‐d]imidazole derivatives are developed as deep‐blue, light‐emitting materials for organic light‐emitting diodes (OLEDs). The 1H‐naphtho[1,2‐d]imidazole based compounds exhibit a significantly superior performance than the 3H‐naphtho[1,2‐d]imidazole analogues in the single‐layer devices. This is because they have a much higher capacity for direct electron‐injection from the cathode compared to their isomeric counterparts resulting in a ground‐breaking EQE (external quantum efficiency) of 4.37% and a low turn‐on voltage of 2.7 V, and this is hitherto the best performance for a non‐doped single‐layer fluorescent OLED. Multi‐layer devices consisting of both hole‐ and electron‐transporting layers, result in identically excellent performances with EQE values of 4.12–6.08% and deep‐blue light emission (Commission Internationale de l'Eclairage (CIE) y values of 0.077–0.115) is obtained for both isomers due to the improved carrier injection and confinement within the emissive layer. In addition, they showed a significantly better blue‐color purity than analogous molecules based on benzimidazole or phenanthro[9,10‐d]imidazole segments. 相似文献
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We have performed a preliminary investigation into the use of ZnSe bulk crystals fabricated by Sumitomo Electric Industries,
Ltd. as substrates for the epitaxial1 deposition of ZnSe-based materials and light emitting devices. A low temperature (<380
°C)in- situ cleaning process has been developed for the (100) oriented ZnSe wafers involving the use of a remotely generated atomic hydrogen
beam. The process produces a (1 × 1) atomically smooth ZnSe surface which is highly suitable for epitaxy. Hall-effect measurements
performed on nitrogen-doped ptype ZnSe/S.I. ZnSe epilayers have revealed free-hole concentrations in the homoepitaxial material
as high as 2.1 × 1017cm−3, so far, with room temperature and 77Khole mobility values of 20 and 100 cm2V
su−1
ins/su−1
, respectively. Finally, green light emitting diodes have been grown on the ZnSe wafers having Cd0.2Zn0.8Se/ ZnSe multiple quantum well active regions which have exhibited electroluminescence peak linewidths around 9.9 nm at room
temperature. 相似文献