共查询到20条相似文献，搜索用时 22 毫秒
1.
Bin Zhang Weiyi Hou Xingchen Ye Shengquan Fu Yi Xie 《Advanced functional materials》2009,19(20):3193-3194
2.
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
3.
A theoretical study of light emission from nanoscale silicon 总被引：1，自引：0，他引：1
The electronic properties of silicon nanostructures are calculated using a timedependent algorithm within the tight-binding approximation. The algorithm includes the electron-hole Coulomb interaction directly without resort to perturbative correction, allowing accurate calculation of excited state properties. The densities of states, fundamental band gaps, photoluminescence energies, and band edge eigenfunctions andk-distributions are calculated for nanostructures up to 100Å in diameter. The effects of size, geometry, surface termination, and surface reconstruction on the electronic properties are investigated. We show that a model in which the primary photoluminescence peak is due to exciton recombination across the fundamental gap, while the secondary infra-red peak is due to recombination of a conduction band electron with a hole in a deep surface trap is consistent with recent observations for both silicon nanocrystals and porous silicon. We infer the geometry of the luminescent region in porous silicon by comparing our calculated results with experimental data on porous silicon samples. 相似文献
4.
Jing Huang Ning Sun Yongqiang Dong Runli Tang Ping Lu Ping Cai Qianqian Li Dongge Ma Jingui Qin Zhen Li 《Advanced functional materials》2013,23(18):2329-2337
Four 4,4′‐bis(1,2,2‐triphenylvinyl)biphenyl (BTPE) derivatives, 4,4′‐bis(1,2,2‐triphenylvinyl)biphenyl, 2,3′‐bis(1,2,2‐triphenylvinyl)biphenyl, 2,4′‐bis(1,2,2‐triphenylvinyl)biphenyl, 3,3′‐bis(1,2,2‐triphenylvinyl)biphenyl and 3,4′‐bis(1,2,2‐triphenylvinyl)biphenyl (oTPE‐mTPE, oTPE‐pTPE, mTPE‐mTPE, and mTPE‐pTPE, respectively), are successfully synthesized and their thermal, optical, and electronic properties fully investigated. By merging two simple tetraphenylethene (TPE) units together through different linking positions, the π‐conjugation length is effectively controlled to ensure the deep‐blue emission. Because of the minor but intelligent structural modification, all the four fluorophores exhibit deep‐blue emissions from 435 to 459 nm with Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of, respectively, (0.16, 0.14), (0.15, 0.11), (0.16, 0.14), and (0.16, 0.16), when fabricated as emitters in organic light‐emitting diodes (OLEDs). This is completely different from BTPE with sky‐blue emission (0.20, 0.36). Thus, these results may provide a novel and versatile approach for the design of deep‐blue aggregation‐induced emission (AIE) luminogens. 相似文献
5.
Ganguri Sarada Woosum Cho Athithan Maheshwaran Vijaya Gopalan Sree Ho‐Yeol Park Yeong‐Soon Gal Myungkwan Song Sung‐Ho Jin 《Advanced functional materials》2017,27(27)
The photoluminescence (PL) efficiency of emitters is a key parameter to accomplish high electroluminescent performance in phosphorescent organic light‐emitting diodes (PhOLEDs). With the aim of enhancing the PL efficiency, this study designs deep‐blue emitting heteroleptic Ir(III) complexes (tBuCN‐FIrpic, tBuCN‐FIrpic‐OXD, and tBuCN‐FIrpic‐mCP) for solution‐processed PhOLEDs by covalently attaching the light‐harvesting functional moieties (mCP‐Me or OXD‐Me) to the control Ir(III) complex, tBuCN‐FIrpic. These Ir(III) complexes show similar deep‐blue emission peaks around 453, 480 nm (298 K) and 447, 477 nm (77 K) in chloroform. tBuCN‐FIrpic‐mCP demonstrates higher light‐harvesting efficiency (142%) than tBuCN‐FIrpic‐OXD (112%), relative to that of tBuCN‐FIrpic (100%), due to an efficient intramolecular energy transfer from the mCP group to the Ir(III) complex. Accordingly, the monochromatic PhOLEDs of tBuCN‐FIrpic‐mCP show higher external quantum efficiency (EQE) of 18.2% with one of the best blue coordinates (0.14, 0.18) in solution‐processing technology. Additionally, the two‐component (deep‐blue:yellow‐orange), single emitting layer, white PhOLED of tBuCN‐FIrpic‐mCP shows a maximum EQE of 20.6% and superior color quality (color rendering index (CRI) = 78, Commission Internationale de L'Eclairage (CIE) coordinates of (0.353, 0.352)) compared with the control device containing sky‐blue:yellow‐orange emitters (CRI = 60, CIE coordinates of (0.293, 0.395)) due to the good spectral coverage by the deep‐blue emitter. 相似文献
6.
利用吸收光谱和光致发光(PL)光谱研究了氢化物气相外延(HVPE)法生长的GaN厚膜材料发光特性。研究发现当激发脉冲光源的重复频率较低时,PL光谱中仅能观察到带边发光峰,当重复频率增加时,PL光谱中不仅出现带边发光峰,还可观察到蓝带发光峰和黄带发光峰;随着光源重复频率的增加,带边发光峰与黄带发光峰、蓝带发光峰的光强之比也随着增大。分析认为蓝带发光起源于材料中碳杂质缺陷而黄带发光可能与位错等结构缺陷有关。 相似文献
7.
Xinyi Cai Bin Gao Xiang‐Long Li Yong Cao Shi‐Jian Su 《Advanced functional materials》2016,26(44):8042-8052
A barely reached balance between weak intramolecular‐charge‐transfer (ICT) and small singlet–triplet splitting energy (ΔEST) for reverse intersystem crossing from non‐emissive triplet state to radiative singlet state impedes the realization of deep‐blue thermally activated delayed fluorescence (TADF) materials. By discarding the twisted‐ICT framework for a flattened molecular backbone and introducing a strong acceptor possessing n–π* transition character, hypsochromic color, a large radiative rate (kF), and small ΔEST are achieved simultaneously. Six molecules with a 9,9‐dimethyl‐10‐phenyl‐9,10‐dihydroacridine (i‐DMAc) donor are synthesized and investigated. Coinciding with time‐dependent density functional theory, the reduced dihedral angles between donor (D) and acceptor (A) weaken ICT from dispersed charge density and enable a large kF from increased frontier molecular orbitals overlap. Despite the separated highest occupied (HOMO) and lowest unoccupied molecular orbital (LUMO) population, the intercalation of phenyl bridges between D–A increases kF but significantly lowers the local triplet excited state, indicating small HOMO and LUMO overlap is not a sufficient, but necessary condition for reduced ΔEST. Integrating short conjugation length and carbonyl or triazine acceptors into the complanation molecules, deep‐blue TADF organic light‐emitting diodes demonstrate maximum external quantum efficiencies of 11.5% and 10.9% with Commission Internationale de l'Eclairage coordinates of (0.16, 0.09) and (0.15, 0.11), respectively, which is quite close to the stringent National Television System Committee blue standard. 相似文献
8.
The halide perovskite blue light emitting diodes (PeLEDs) attracted many researchers because of its fascinating opto-electrical properties.This review introduces the recent progress of blue PeLEDs which focuses on emissive layers and interlay-ers.The emissive layer covers three types of perovskite structures:perovskite nanocrystals (PeNCs),2-dimensional (2D) and quasi-2D perovskites,and bulk (3D) perovskites.We will discuss about the remaining challenges of blue PeLEDs,such as lim-ited performances,device instability issues,which should be solved for blue PeLEDs to realize next generation displays. 相似文献
9.
金属卤化物掺杂钙钛矿纳米晶体（NCs）已被证明可以通过精确控制非辐射复合来提高光致发光量子产率（PLQY）。通过热注入法合成了三价镧系元素卤化物氯化钕掺杂的钙钛矿蓝光量子点,通过X射线光电子能谱（XPS）观察到Nd 3d和Cl 2p的核心峰,这说明Nd3 +和Cl-成功掺杂到NCs中。这些蓝光Nd3+-CsPb（Br/Cl）3量子点具有较高的光致发光量子产率,并且随着Nd3+掺杂量的增多,其光热稳定性得到很大提升。 相似文献
10.
Hongxu Liao Ming Zhao Yayun Zhou Maxim S. Molokeev Quanlin Liu Qinyuan Zhang Zhiguo Xia 《Advanced functional materials》2019,29(30)
A robust and stable narrow‐band green emitter is recognized as a key enabler for wide‐color‐gamut liquid crystal display (LCD) backlights. Herein, an emerging rare earth silicate phosphor, RbNa(Li3SiO4)2:Eu2+ (RN:Eu2+) with exceptional optical properties and excellent thermal stability, is reported. The resulting RN:Eu2+ phosphor presents a narrow green emission band centered at 523 nm with a full width at half maximum of 41 nm and excellent thermal stability (102%@425 K of the integrated emission intensity at 300 K). RN:Eu2+ also shows a high quantum efficiency, an improved chemical stability, and a reduced Stokes shift owing to the modified local environment, in which [NaO8] cubes replace [LiO4] squares in RbLi(Li3SiO4)2:Eu2+ via polyhedron transformation. White light‐emitting diode (wLED) devices with a wide color gamut (113% National Television System Committee (NTSC)) and high luminous efficacy (111.08 lm W?1) are obtained by combining RN:Eu2+ as the green emitter, K2SiF6:Mn4+ as the red emitter, and blue‐emitting InGaN chips. Using these wLEDs as backlights, a prototype 20.5 in. LCD screen is fabricated, demonstrating the bright future of stable RN:Eu2+ for wide‐color‐gamut LCD backlight application. 相似文献
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ZnS films were deposited on porous Si (PS) substrates using a pulsed laser deposition (PLD) technique.White light emission is observed in photoluminescence (PL) spectra, and the white light is the combination of blue and green emission from ZnS and red emission from PS. The white PL spectra are broad, intense in a visible band ranging from 450 to 700 nm. The effects of the excitation wavelength, growth temperature of ZnS films, PS porosity and annealing temperature on the PL spectra of ZnS/PS were also investigated. 相似文献
13.
Xiaomin Guo Peisen Yuan Xianfeng Qiao Dezhi Yang Yanfeng Dai Qian Sun Anjun Qin Ben Zhong Tang Dongge Ma 《Advanced functional materials》2020,30(9)
Aggregation‐induced emission (AIE) materials are highly attractive because of their excellent properties of high efficiency emission in nondoped organic light‐emitting diodes (OLEDs). Therefore, a deep understanding of the working mechanisms, further improving the electroluminescence (EL) efficiency of the resulting AIE‐based OLEDs, is necessary. Herein, the conversion process from higher energy triplet state (T2) to the lowest singlet state (SS1) is found in OLEDs based on a blue AIE material, 4′‐(4‐(diphenylamino)phenyl)‐5′‐phenyl‐[1,1′:2′,1′′‐terphenyl]‐4‐carbonitrile (TPB‐AC), obviously relating to the device efficiency, by magneto‐EL (MEL) measurements. A special line shape with rise at low field and reduction at high field is observed. The phenomenon is further clarified by theoretical calculations, temperature‐dependent MELs, and transient photoluminescence emission properties. On the basis of the T2‐S1 conversion process, the EL performances of the blue OLEDs based on TPB‐AC are further enhanced by introducing a phosphorescence doping emitter in the emitting layer, which effectively regulates the excitons on TPB‐AC molecules. The maximum external quantum efficiency (EQE) reaches 7.93% and the EQE keeps 7.57% at the luminance of 1000 cd m?2. This work establishes a physical insight for designing high‐performance AIE materials and devices in the future. 相似文献
14.
Yoshimitsu Sagara Shogo Yamane Toshiki Mutai Koji Araki Takashi Kato 《Advanced functional materials》2009,19(12):1869-1875
Here, a photoluminescent liquid crystal that exhibits a change of emission color on the metastable–stable phase transition induced by external stimuli is prepared. A 2,6‐diethynylanthracene derivative with amide groups and dendritic side chains exhibits a columnar phase on slow cooling from the isotropic phase and shows blue emission in this columnar phase. In contrast, a cubic phase is obtained by rapid cooling from the isotropic phase. In the cubic phase, the 2,6‐diethynylanthracene cores form excimers, resulting in yellow emission. While the columnar phase is a stable liquid‐crystalline (LC) phase, the cubic phase is a metastable LC phase. It is found that a change of the photoluminescent color from yellow to blue is observed on the cubic‐columnar phase transition induced by heating or mechanical shearing for this 2,6‐diethynylanthracene derivative in the cubic phase. This change of photoluminescent color is ascribed to the inhibition of excimer formation on the metastable–stable LC phase transition. 相似文献
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We studied the dependence of the photoluminescence emission energy of InGaAs/AlGaAs quantum dot (QD) structures grown by molecular
beam epitaxy as a function of the Al and In content in barriers and QDs, respectively. We show that emissions are blue-shifted
by increasing both the Al content in the 0 to 0.30 range and, unexpectedly, the In composition in the 0.4 to 0.7 range; we
suggest that such results stem from significant changes in QD sizes, shapes, and composition profiles. This research led to
the preparation of structures with efficient light emission in the 980 nm window of optoelectronic interest. 相似文献
17.
用电化学方法制备了一定孔隙率的多孔硅(PS)样品,然后用脉冲激光沉积(PLD)法以多孔硅为衬底生长一层ZnS薄膜.ZnS的带隙较宽,对可见光是透明的,用适当波长的光激发,PS发射的橙红光可以透过ZnS薄膜,与ZnS的蓝绿光相叠加,得到了可见光区较宽的光致发光带,呈现较强的白光发射.用x射线衍射仪(XRD)和扫描电子显微镜(SEM)表征了ZnS薄膜的结构性质.结果表明,沉积的ZnS薄膜结晶质量较差,薄膜表面起伏不平.这是由于衬底PS的表面不平整所致. 相似文献
18.
Shih‐Chun Lo Raghu N. Bera Ruth E. Harding Paul L. Burn Ifor D. W. Samuel 《Advanced functional materials》2008,18(19):3080-3090
Solution‐processible saturated blue phosphorescence is an important goal for organic light‐emitting diodes (OLEDs). Fac‐tris(5‐aryltriazolyl)iridium(III) complexes can emit blue phosphorescence at room temperature. Mono‐ and doubly dendronized fac‐tris(1‐methyl‐5‐phenyl‐3‐n‐propyl‐1H‐[1,2,4]triazolyl)iridium(III) 1 and fac‐tris{1‐methyl‐5‐(4‐fluorophenyl)‐3‐n‐propyl‐1H‐[1,2,4]triazolyl}iridium(III) 4 with first generation biphenyl‐based dendrons were prepared. The dendrimers emitted blue light at room temperature and could be solution processed to form thin films. The doubly dendronized 3 had a film photoluminescence quantum yield of 67% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.17, 0.33). OLEDs comprised of a neat film of dendrimer 3 and an electron transport layer achieved a brightness of 142 cd m?2 at 3.8 V with an external quantum efficiency of 7.9%, and CIE coordinates of (0.18, 0.35). Attachment of the fluorine atom to the emissive core had the effect of moving the luminescence to shorter wavelengths but also quenched the luminescence of the mono‐ and doubly dendronized dendrimers. 相似文献
19.
Wei Deng Xiangcheng Jin You Lv Xiujuan Zhang Xiaohong Zhang Jiansheng Jie 《Advanced functional materials》2019,29(40)
Ruddlesden–Popper perovskite, (PEA)2PbBr4 (PEA = C8H9NH3), is a steady and inexpensive material with a broad bandgap and a narrow‐band emission. These features make it a potential candidate for deep‐blue light‐emitting diodes (LEDs). However, due to the weak exciton binding energy, LEDs based on the perovskite thin films usually possess a very low external quantum efficiency (EQE) of <0.03%. Here, for the first time, the construction of high‐performance deep‐blue LEDs based on 2D (PEA)2PbBr4 nanoplates (NPs) is demonstrated. The as‐fabricated (PEA)2PbBr4 NPs film shows a deep‐blue emission at 410 nm with excellent stability under ambient conditions. Impressively, LEDs based on the (PEA)2PbBr4 NPs film deliver a bright deep‐blue emission with a maximum luminance of 147.6 cd m?2 and a high EQE up to 0.31%, which represents the most efficient and brightest perovskite LEDs operating at deep‐blue wavelengths. Furthermore, the LEDs retain over 80% of their efficiencies for over 1350 min under ≈60% relative humidity. The steady and bright deep‐blue LEDs can be used as an excitation light source to realize white light emission, which shows the potential for light communication. The work provides scope for developing perovskite into efficient and deep‐blue LEDs for low‐cost light source and light communication. 相似文献
20.
Tin sulphide(SnS) thin films have been recognized as a potential candidate for solar cells. Many fabrication techniques have been used to grow SnS thin films. The band-gap, Eg of SnS films as reported in literature, were found to vary from 1.2-2.5 eV depending on the film fabrication technique. The present work reports the structural, compositional, morphological and optical characterization of SnS thin films fabricated by thermal evaporation at room temperature. Results show that for the given fabrication technique/condition, the band-gap functionally depends on the lattice parameter and grain size. The well-defined variation allows for tailoring SnS film as per requirements. 相似文献
