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Erwan Rauwel Augustinas Galeckas Protima Rauwel Helmer Fjellvåg 《Advanced functional materials》2012,22(6):1174-1179
This article reports on optical properties of SrHfO3 and CaHfO3 nanoparticles with sizes as small as 1.6 nm, synthesized via non aqueous sol–gel routs for the first time. An unexpectedly strong luminescence from the undoped nanoparticles was observed in the visible spectrum over a wide temperature range, also exhibiting sensitivity to temperature variation and surrounding ambient (vacuum/air) and exposure time to UV light. A tentative model is proposed to explain these phenomena in terms of luminescent centers located at the surface of the nanoparticles. 相似文献
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Yang Fang Wei Liu Simon J. Teat Gangotri Dey Zeqing Shen Litao An Dechao Yu Lu Wang Deirdre M. O'Carroll Jing Li 《Advanced functional materials》2017,27(3)
The authors have designed and synthesized a family of high‐performance inorganic–organic hybrid phosphor materials composed of extended and robust networks of one, two, and three dimensions. Following a bottom‐up solution‐based synthetic approach, these structures are constructed by connecting highly emissive Cu4I4 cubic clusters via carefully selected ligands that form strong Cu? N bonds. They emit intensive yellow‐orange light with high luminescence quantum efficiency, coupled with large Stokes shift, which greatly reduces self‐absorption. They also demonstrate exceptionally high framework‐ and photostability, comparable to those of commercial phosphors. The high stabilities are the result of significantly enhanced Cu? N bonds, as confirmed by the density functional theory (DFT) binding energy and electron density calculations. Possible emission mechanisms are analyzed based on the results of theoretical calculations and optical experiments. Two‐component white phosphors obtained by blending blue and yellow emitters reach an internal quantum yield as high as 82% and correlated color temperature as low as 2534 K. The performance level of this subfamily exceeds all other types of Cu–I based hybrid systems. The combined advantages make them excellent candidates as alternative rare‐earth element‐free phosphors for possible use in energy‐efficient lighting devices. 相似文献
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《Advanced functional materials》2018,28(24)
The demonstration of reliable and stable white light‐emitting diodes (LEDs) is one of the main technological challenges of the LED industry. This is usually accomplished by incorporation of light‐emitting rare‐earth elements (REEs) compounds within an external polymeric coating of a blue LED allowing the generation of white light. However, due to both environmental and cost issues, the development of low‐cost REE‐free coatings, which exhibit competitive performance compared to conventional white LED is of great importance. In this work, the formation of an REE‐free white LED coating is demonstrated. This biocomposite material, composed of biological (crystalline nanocellulose and porcine gastric mucin) and organic (light‐emitting dyes) compounds, exhibits excellent optical and mechanical properties as well as resistance to heat, humidity, and UV radiation. The coating is further used to demonstrate a working white LED by incorporating it within a commercial blue LED. 相似文献
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Heyong Wang Zhan Chen Jingcong Hu Hongling Yu Chaoyang Kuang Jiajun Qin Xianjie Liu Yue Lu Mats Fahlman Lintao Hou Xiao-Ke Liu Feng Gao 《Advanced functional materials》2021,31(8):2007596
Despite quick development of perovskite light-emitting diodes (PeLEDs) during the past few years, the fundamental mechanisms on how ion migration affects device efficiency and stability remain unclear. Here, it is demonstrated that the dynamic redistribution of mobile ions in the emissive layer plays a key role in the performance of PeLEDs and can explain a range of abnormal behaviours commonly observed during the device measurement. The dynamic redistribution of mobile ions changes charge–carrier injection and leads to increased recombination current; at the same time, the ion redistribution also changes charge transport and results in decreased shunt resistance current. As a result, the PeLEDs show hysteresis in external quantum efficiencies (EQEs) and radiance, that is, higher EQEs and radiance during the reverse voltage scan than during the forward scan. In addition, the changes on charge injection and transport induced by the ion redistribution also well explain the rise of the EQE/radiance values under constant driving voltages. The argument is further rationalized by adding extra formamidinium iodide (FAI) into optimized PeLEDs based on FAPbI3, resulting in more significant hysteresis and shorter operational stability of the PeLEDs. 相似文献
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一种红光增强型白光LED特性研究 总被引：2，自引：1，他引：1
为了使白光LED光谱中红光成分增强,以更适应人眼视觉,通过对YAG:Ce荧光粉掺杂的改进,引入Gd3+、Pr3+使白光LED光谱在610 nm处出现明显发射峰,并且荧光主峰发生红移。通过对LED的色坐标计算表明,用这种新型荧光粉封装的白光LED色坐标可以达到标准白点(0.33,0.33),理论上有可能符合\"能源之星\"的要求,用YAG:Ce封装的LED却不可能。 相似文献
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Masoud Alahbakhshi Aditya Mishra Grigorii Verkhogliadov Emigdio E. Turner Ross Haroldson Austen C. Adams Qing Gu Jeffrey J. Rack Jason D. Slinker Anvar A. Zakhidov 《Advanced functional materials》2023,33(28):2214315
Perovskite light-emitting diodes (PeLEDs) are advancing because of their superior external quantum efficiencies (EQEs) and color purity. Still, additional work is needed for blue PeLEDs to achieve the same benchmarks as the other visible colors. This study demonstrates an extremely efficient blue PeLED with a 488 nm peak emission, a maximum luminance of 8600 cd m−2, and a maximum EQE of 12.2% by incorporating the double-sided ethane-1,2-diammonium bromide (EDBr2) ligand salt along with the long-chain ligand methylphenylammonium chloride (MeCl). The EDBr2 successfully improves the interaction between 2D perovskite layers by reducing the weak van der Waals interaction and creating a Dion–Jacobson (DJ) structure. Whereas the pristine sample (without EDBr2) is inhibited by small stacking number (n) 2D phases with nonradiative recombination regions that diminish the PeLED performance, adding EDBr2 successfully enables better energy transfer from small n phases to larger n phases. As evidenced by photoluminescence (PL), scanning electron microscopy (SEM), and atomic force microscopy (AFM) characterization, EDBr2 improves the morphology by reduction of pinholes and passivation of defects, subsequently improving the efficiencies and operational lifetimes of quasi-2D blue PeLEDs. 相似文献
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Ziv Hameiri Arman Mahboubi Soufiani Mattias K. Juhl Liangcong Jiang Fuzhi Huang Yi‐Bing Cheng Henner Kampwerth Juergen W. Weber Martin A. Green Thorsten Trupke 《Progress in Photovoltaics: Research and Applications》2015,23(12):1697-1705
Fast camera‐based luminescence‐imaging measurements on perovskite solar cells are presented. The fundamental correlation between the luminescence intensity and the open circuit voltage predicted by the generalised Planck law is confirmed, enabling various quantitative methods for the detection of efficiency‐limiting defects to be applied to this new cell structure. Interstinegly, it is found that this fundamental correlation is valid only for light‐soaked devices. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
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基于水溶性感光胶的白光LEDs平面涂层技术,在蓝光LED芯片表面上得到了可控的荧光粉层.采用降低粉浆中ADC的浓度和提高荧光粉的含量两种措施,减少Cr3+在433.6和620nm两处吸收对器件出光效率的影响;新配制的粉浆在暗室中静置3～5h,既可以提高器件的出光效率同时又避免了暗反应带来的影响;在蓝光LED表面上得到粉层后,再涂覆硅胶层,由于硅胶的折射率与粉层的更接近,不但使出光色调偏向蓝光区域而且有更多光子出射,光通量由未加硅胶层时的44.8～59 lm提高到了79.4～84.9 lm. 相似文献
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提高基于粉浆法的功率型白光LEDs发光效率的研究 总被引：1，自引：1，他引：0
基于水溶性感光胶的自光LEDs平面涂层技术,在蓝光LED芯片表面上得到了可控的荧光粉层．采用降低粉浆中ADC的浓度和提高荧光粉的含量两种措施,减少Cr^3＋在433．6和620nm两处吸收对器件出光效率的影响;新配制的粉浆在暗室中静置3～5h,既可以提高器件的出光效率同时又避免了暗反应带来的影响;在蓝光LED表面上得到粉层后,再涂覆硅胶层,由于硅胶的折射率与粉层的更接近,不但使出光色调偏向蓝光区域而且有更多光子出射,光通量由未加硅胶层时的44．8～59lm提高到了79．4～84．9lm． 相似文献
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在LED封装过程中,大家往往很容易忽略一些辅料对LED产品质量的影响,从而造成不良率过高,良品率低,成本增加。本文主要讲述辅料离模剂使用量的多少对直插式LED的影响。 相似文献
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Organic-inorganic hybrid perovskite have recently drawn appreciable attention for applications in light-emitting diodes (LEDs). However, the weak exciton binding energy of the methylammonium lead iodide perovskite introduces large exciton dissociation and low radiative recombination on its application as emission layer in near-infrared LEDs. Herein, we demonstrate the simple method by incorporating of phenethylammonium iodide (PEAI) into the perovskite can concurrently improve the radiative recombination rate for improving perovskite LED performances. Additionally, by introducing PEAI dramatically constrains the growth of perovskite crystals during film forming, producing crystallites with small dimensions, reducing roughness, and pin-hole free. After optimizing the emission layer in the perovskite LED, a high optical output power of 458.03 μW and external quantum efficiency of 5.25% are achieved, which represents a ~50-fold enhancement in the quantum efficiency compared to device without PEAI. Our work suggests a broad application prospect of perovskite materials for high optical output power LEDs and eventually a potential for solution-processed electrically pumped NIR laser diodes. 相似文献
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Azhar Fakharuddin Weiming Qiu Guillaume Croes Andrius Deviis Rokas Gegevi
ius Alexander Vakhnin Cedric Rolin Jan Genoe Robert Gehlhaar Andrey Kadashchuk Vidmantas Gulbinas Paul Heremans 《Advanced functional materials》2019,29(37)
Perovskite light emitting diodes (PeLEDs) have reached external quantum efficiencies (EQEs) over 21%. Their EQE, however, drops at increasing current densities (J) and their lifetime is still limited to just a few hours. The mechanisms leading to EQE roll‐off and device instability require thorough investigation. Here, improvement in EQE, EQE roll‐off, and lifetime of PeLEDs is demonstrated by tuning the balance of electron/hole transport into a mixed 2D/3D perovskite emissive layer. The mixed 2D/3D perovskite layer induces exciton confinement and beneficially influences the electron/hole distribution inside the perovskite layer. By tuning the electron injection to match the hole injection in such active layer, a nearly flat EQE for J = 0.1–200 mA cm?2, a reduced EQE roll‐off until J = 250 mA cm?2, and a half‐lifetime of ≈47 h at J = 10 mA cm?2 is reached. A model is also proposed to explain these improvements that account for the spatial electron/hole distributions. 相似文献
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Shuai Yuan Qing‐Wei Liu Qi‐Sheng Tian Yan Jin Zhao‐Kui Wang Liang‐Sheng Liao 《Advanced functional materials》2020,30(12)
Perovskite‐based light‐emitting diodes (PeLEDs) have exhibited promising potential; however, their operational lifetimes are far from expectation. The large bias of the device during operation has been demonstrated as one of main reasons for accelerated device failure. To mitigate such a predicament, interfacial Auger effect (IAE) assisted sub‐bandgap voltage electroluminescence (EL) is a potential pathway to decrease the electric field intensity in each functional layer. However, the properties of a desirable IAE are still poorly understood. Herein, the underlying mechanism of IAE based on the injection characteristics of interfacial minority carriers at the Auger effect interface is investigated. Consequently, the prerequisites and the secondary conditions for the realization of IAE are proposed. Taking advantage of IAE assisted EL, the fabricated PeLEDs exhibit ultralow operational voltage, ignorable roll‐off, and improved operational stability. The findings in this work not only pave the way toward a feasible approach to enhance the stability of PeLEDs, but also highlight the potential of sub‐bandgap voltage EL in future display and lighting applications, especially in series circuits and tandem structures. 相似文献
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利用自行研制的InGaN GaNSQW蓝光LED芯片和YAG :Ge3 荧光粉制作了高亮度白光LED(Φ3) ,并对其发光强度、色度坐标、I V、色温及显色性等特性进行了研究 .实验结果表明 :室温下 ,正向电流为 2 0mA时 ,白光LED的轴向发光强度为 1 1～ 2 3cd ,正向电压小于 3 5V ,色度坐标为 (0 2 8,0 34) ,显色指数约为 70 . 相似文献
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Among the inorganic phosphors used in advanced lighting technologies, rare‐earth doped nitridosilicates have attracted significant attention because they exhibit superior photoluminescence properties in connection with high thermal, chemical, and mechanical stabilities. All of these materials are crystalline, which imposes substantial limitations in discovering new phosphors, since the activators to be included in the host matrix need to comply closely with the respective lattice sites, at least with respect to charge and size. As an approach to overcome such implications, an amorphous matrix, namely Si3B3N7, is suggested as a universal nitride‐based host accessible to (co)dope various activators, e.g., Eu2+, Ce3+ and Tb3+. Unlike crystalline phosphors, in the amorphous Si3B3N7 matrix, activator ions do not replace any atom from the random network host; instead, they act as network modifiers. The synthesis of this new class of amorphous phosphors is based on a precursor route, enabling high purities, and avoiding harsh temperature treatments. 相似文献