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Search Results: 1 - 10 of 4174 matches for " light-emitting conjugated oligomers "
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Prediction of Excitation Energies for Conjugated Oligomers and Polymers from Time-Dependent Density Functional Theory
Jianmin Tao,Sergei Tretiak,Jian-Xin Zhu
Materials , 2010, DOI: 10.3390/ma3053430
Abstract: With technological advances, light-emitting conjugated oligomers and polymers have become competitive candidates in the commercial market of light-emitting diodes for display and other technologies, due to the ultralow cost, light weight, and flexibility. Prediction of excitation energies of these systems plays a crucial role in the understanding of their optical properties and device design. In this review article, we discuss the calculation of excitation energies with time-dependent density functional theory, which is one of the most successful methods in the investigation of the dynamical response of molecular systems to external perturbation, owing to its high computational efficiency.
Polímeros conjugados como camada ativa de diodos emissores de luz e fotodetectores
Hümmelgen, Ivo A.;Roman, Lucimara S.;Lima, Joaquim R. de;
Polímeros , 1998, DOI: 10.1590/S0104-14281998000300008
Abstract: in this paper we present an introduction to conjugated polymers as materials with a set of promising properties for applications in organic light emitting diodes and in organic photodetectors. we start with a short description of the physical properties of conjugated polymers, emphasising its potential for device construction. the difficulties inherent to the construction of conjugated polymer-based devices are discussed and the problems that limit device efficiency are listed.
Study of electroluminescence and electron injection on novel red polyelectrolytes copolymer

Hou Lin-Tao,Huang Fei,Peng Jun-Biao,Cao Yong,

物理学报 , 2007,
Abstract: Single-layer polymer light-emitting diodes with high work function gold cathode were fabricated using a series of novel conjugated polyelectrolytes and their neutral precursors: aminoalkyl-substituted polyfluorenes with different 4,7-di-2-thienyl-2,1,3-benzothiadiazole contents. At the current density of 38.7mA/cm2, the external efficiency reaches 0.42% with the Commission Internationale de I'Eclairage coordinates x=0.67 and y=0.33 for PFN-DBT10. It has been shown that these polymers also can be used as electron injection layer in double-layer devices with high work function gold cathode, which favors the manufacture of solution processing multilayer devices. Based on single-layer and double-layer device structures, it was found that the improvement of device performance is attributed to the interface effect between gold cathode and polyelectrolytes layer.

SHI Wei,FAN Suqin,WANG Lei,YANG Wei,CAO Yong,

高分子学报 , 2009,
Abstract: 通过水相Suzuki偶合反应合成了两种磺酸盐基团取代的三苯胺类共轭聚电解质PTP11和PTP31,对其化学结构进行了表征.通过对其光学和电化学性能进行测试得知,此类聚合物具有和ITO功函数相近的HOMO能级及较高的LUMO能级.磺酸盐基团的存在使得此类聚电解质具有和电中性聚合物所不同的溶解性,当其作为空穴传输材料应用于多层结构的聚合物电致发光器件(PLED)中时,可有效避免空穴传输层-发光层之间的界面混溶问题.以这两种聚合物作为空穴传输材料应用于以PFO-DBT15为发光层的红光PLEDs中时,器件的性能得到了显著提高.此外,磺酸盐基团的不同取代方式会对器件的性能产生一定的影响.
Effect of Pixellization on Efficiency and Stability of MEH-PPV Based Polymer Light-Emitting Diodes  [PDF]
Ranbir Singh, Monica Katiyar
Journal of Encapsulation and Adsorption Sciences (JEAS) , 2012, DOI: 10.4236/jeas.2012.21002
Abstract: Organic light-emitting diodes are generally depicted as sequential deposition of active layers and electrodes onto a substrate, but commercial devices are fabricated using pixellization technique, where an insulator layer is introduced between the indium tin oxide and organic layer to define the area of the active device. Here, we have inserted a layer of photoresist (thickness ~ 200 nm) at the edge of patterned anode (indium tin oxide) and between the anode and hole transport layer (Poly 3, 4-ethylenedioxythiophene poly styrenesulfonate) to examine its effect on the leakage current of organic light-emitting diode and on the electron-hole recombination ratio in the emission area, as a result increasing the luminance efficiency. Current leakage causes the loss of charges, which adversely affects the recombination of electrons and holes in the emitting zone and results in poorer luminance efficiency. In this paper, we report the effect of pixellization on current density-voltage, luminescence-voltage and degradation behavior of single layer Poly[2-methoxy-5-(2’-ethylhexyloxy)-1, phenylene vinylene] based organic light-emitting diodes. Devices with isolation layer have 30% higher external electroluminescence quantum efficiency and reduced device degradation in comparison to without isolation layer.
Stability study of saturated red polymer light-emitting diodes
Wei Xu,JunBiao Peng,YunHua Xu,Jian Wang,Zhe Huang,QiaoLi Niu,Yong Cao
Chinese Science Bulletin , 2007, DOI: 10.1007/s11434-007-0173-5
Abstract: Saturated red polymer light-emitting diodes have been fabricated with a single emitting polymer blend layer of poly[2-(2-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV) and poly[9,9-dioctylfluorene-co-4,7-di-2-thienyl-2,1,3-benzothiadiazole] (PFO-DBT15). Saturated red emission with the Commission Internationale de l’Eclairage (CIE) coordinates of (0.67, 0.33) was obtained. The device stability was investigated. The results showed that energy transfer occurred from MEH-PPV to PFO-DBT15, and MEH-PPV improved the hole injection and transportation.
A novel yellow emitting phosphor Dy3+, Bi3+ co-dopedYVO4 potentially for white light emitting diodes

Ci Zhi-Peng,Wang Yu-Hua,Zhang Jia-Chi,

中国物理 B , 2010,
Abstract: Novel Y$_{1 - x - y}$VO$_{4}$:$x$Dy$^{3 + }$, $y$Bi$^{3 + }$ ($0.01 \le x \le 0.05, 0 \le y \le 0.20$) phosphors for light emitting diode (LED) were successfully synthesised by solid-state reaction. The calculation results of electronic structure show that YVO$_{4}$ has a direct band gap with 3~eV at $G$. The top of the valence band is dominated by O 2p state and the bottom of the conduction band is mainly composed of O 2p and V 3d states. An efficient yellow emission under near-ultraviolet (365 nm) excitation is observed. Compared with the pure YVO$_{4}$:Dy$^{3 + }$ samples, the Dy$^{3 + }$, Bi$^{3 + }$ co-doped samples show a more intensive emission peak (at 574~nm) and a new broad emission band (450--770~nm), due to the $^{4}F_{9 / 2}-{}^{6}H_{13 / 2 }$ transition of Dy$^{3 + }$ and the emission of the VO$_{4}^{3 - }-$Bi$^{3 + }$ complex respectively. The optimum chromaticity index of Y$_{1 - x - y}$VO$_{4}$:$x$Dy$^{3 + }$, $y$Bi$^{3 + }$ ($0.01 \le x \le 0.05, 0 \le y \le 0.20$) is (0.447, 0.497), which indicates that YVO$_{4}$:Dy$^{3 + }$, Bi$^{3 + }$ has higher colour saturation than the commercial phosphor YAG: Ce$^{3 + }$. The effects of concentration of Dy$^{3 + }$, Bi$^{3 + }$, electric states and the photoluminescence properties are discussed in details.
Electronic Two-Transition-Induced Enhancement of Emission Efficiency in Polymer Light-Emitting Diodes
Ren-Ai Chen,Cong Wang,Sheng Li,Thomas F. George
Materials , 2013, DOI: 10.3390/ma6030886
Abstract: With the development of experimental techniques, effective injection and transportation of electrons is proven as a way to obtain polymer light-emitting diodes (PLEDs) with high quantum efficiency. This paper reveals a valid mechanism for the enhancement of quantum efficiency in PLEDs. When an external electric field is applied, the interaction between a negative polaron and triplet exciton leads to an electronic two-transition process, which induces the exciton to emit light and thus improve the emission efficiency of PLEDs.
Light emitting diode as a photorefectance pump source
Leonardo Dias de Souza,Ivan Frederico Lupiano Dias,Edson Laureto,Dari Oliveira Toginho Filho
Semina : Ciências Exatas e Tecnológicas , 2008,
Abstract: Light-emitting diodes (LEDs) with different wavelengths are used as photorefectance light pump sources. Photorefectance spectra of bulk semiconductors of GaAs and GaAs/InGaP and GaAsSbN/GaAs heterostructures prepared on GaAs substrates were investigated, using blue, green, orange and red LEDs, in comparison with spectra obtained with the use of Ar and He-Ne lasers, using a conventional technique. Results show the possibility of using LEDs as pump light sources in photorefectance measurements.
Device Fabrication of 60 μm Resonant Cavity Light-Emitting Diode
J. J. C. Reyes,W. Bisquerra,R. V. Sarmago,A. A. Salvador
Science Diliman , 2004,
Abstract: An array of 60-mm-diameter resonant cavity light-emitting diodes suited for coupling with fiber opticwere fabricated using standard device fabrication technique. I-V characterization was used to determinethe viability of the device fabricating process. Under forward bias, the turn-on voltage of the devices is1.95–2.45 V with a series resistance of 17–14 kW. Under reverse bias, the devices showed a breakdownvoltage of 35 V.
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