共轭聚合物材料及电致发光器件

共轭聚合物是一种极有应用前景的有机半导体材料,本文综述其研究进展,包括典型共轭聚合物材料PPV、PT、PF等及PPP的工作原理,发展前景和存在的问题。     

New hole-transport polyurethanes applied to polymer light-emitting diodes

Polymeric light-emitting diodes (PLEDs) using high-performance hole-transport polyurethanes (PUs) have been fabricated. The PUs were prepared from the condensation polymerization of (E, E)-1,4-bis(2-hydroxystyryl)benzene, an oligo para-phenylene-(E)-vinylene (OPV) unit, with toluene diisocyanate (TDI), isophorone diisocyanate (IPDI) or dicyclohexylmethane 4,4′-diisocyanate (H₁₂MDI), respectively. The condensation polymerization was end-capped with 4-tert-butylphenol as the terminal group. The PLED having the PU layer inserted between PEDOT:PSS (HIL) and MEH-PPV (EML) demonstrated superior current efficiency and low turn-on voltage when comparing to the reference devices of ITO/MEH-PPV(50 nm)/Ca(10 nm)/Ag(100 nm) as well as ITO/PEDOT:PSS(30 nm)/MEH-PPV(50 nm)/Ca(10 nm)/Ag(100 nm). In particularly, the best device performance was realized with the PU of OPV-IPDI as the hole-transport layer, resulting 53 times and 2.72 times of current efficiency enhancement as well as 1.5 V and 1 V voltage reduction of the turn-on voltage, respectively, when compared against the reference devices. Besides, our experiments also showed that the PU polymer could also be applied for flexible PLED with similar performance enhancement. Based on the promising results, we concluded that OPV-IPDI was a good hole-transport material for light-emitting diode application.     

Fluorene-based copolymers for color-stable blue light-emitting diodes

A series of random conjugated copolymers (PFO-HBT) derived from 9,9-dioctylfluorene (DOF) and 2-hexylbenzotriazole (HBT) is prepared by the palladium-catalyzed Suzuki coupling reaction with the feed HBT molar ratio around 1%, 5% and 15%. By copolymerizing 2-hexylbenzotriazole into the backbone of polyfluorene, an efficient colorfast blue light-emitting polymer system is developed. The device with the structure of ITO (indium tin oxide)/PEDOT/PVK/PFO-HBT1/Ba/Al exhibits the highest external quantum efficiency 1.62% with luminance efficiency of 2.69 cd/A, power efficiency of 1.25 lm/W and the CIE coordinates of (0.15, 0.17). The EL spectra are stable at the increased current density and continuous operation without significant change of CIE.     

A robust yellow-emitting metallophosphor with electron-injection/-transporting traits for highly efficient white organic light-emitting diodes

With the aim of endowing triplet emitters in the development of organic light-emitting devices (OLEDs) with electron-injection/-transporting (EI/ET) features, the phenylsulfonyl moiety was introduced into the phenyl ring of a 2-phenylpyridine (Hppy) ligand and the yellow phosphorescent heteroleptic iridium(III) complex 1 was developed. It was shown that the SO(2)Ph unit could provide EI/ET character to 1, as indicated from both electrochemical and computational data. Complex 1 is a promising yellow-emitting material for both monochromatic OLEDs and white OLEDs (WOLEDs). The outstanding electronic traits associated with 1, coupled with careful device design, afforded very attractive electroluminescent performances for two-element WOLEDs, including a low turn-on voltage of less than 3.7 V, a maximum brightness of 48,000 cd m(-2), an external quantum efficiency of 13.0%, a luminance efficiency of 34.7 cd A(-1), and a power efficiency of 24.3 Lm W(-1). In addition, a good color rendering index (CRI) of about 74, a stable white color with a Commission Internationale de L'Eclairage (CIE(x,y)) variation of Δ(x, y) < ±(0.02, 0.02), and a correlated color temperature higher than 5130 K were obtained. These encouraging results indicate the potential of these WOLEDs as good candidates for warm indoor lighting sources, as well as the critical contribution of such key EI/ET properties to triplet emitters to advance new OLED research.     

Hole‐transporting host‐polymer series consisting of triphenylamine basic structures for phosphorescent polymer light‐emitting diodes

A series of novel styrene derived monomers with triphenylamine‐based units, and their polymers have been synthesized and compared with the well‐known structure of polymer of N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine with respect to their hole‐transporting behavior in phosphorescent polymer light‐emitting diodes (PLEDs). A vinyltriphenylamine structure was selected as a basic unit, functionalized at the para positions with the following side groups: diphenylamine, 3‐methylphenyl‐aniline, 1‐ and 2‐naphthylamine, carbazole, and phenothiazine. The polymers are used in PLEDs as host polymers for blend systems with the following device configuration: glass/indium–tin–oxide/PEDOT:PSS/polymer‐blend/CsF/Ca/Ag. In addition to the hole‐transporting host polymer, the polymer blend includes a phosphorescent dopant [Ir(Me‐ppy)₃] and an electron‐transporting molecule (2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole). We demonstrate that two polymers are excellent hole‐transporting matrix materials for these blend systems because of their good overall electroluminescent performances and their comparatively high glass transition temperatures. For the carbazole‐substituted polymer (T_g = 246 °C), a luminous efficiency of 35 cd A^?1 and a brightness of 6700 cd m^?2 at 10 V is accessible. The phenothiazine‐functionalized polymer (T_g = 220 °C) shows nearly the same outstanding PLED behavior. Hence, both these polymers outperform the well‐known polymer of N,N′‐bis(3‐methylphenyl)‐N,N′‐diphenylbenzidine, showing only a luminous efficiency of 7.9 cd A^?1 and a brightness of 2500 cd m^?2 (10 V). © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3417–3430, 2010     

SrTiO3/TiO2 Hybridstructure as Photoanode in Dye‐Sensitized Solar Cell

In dye‐sensitized solar cells (DSSCs), the charge recombination at the TiO₂/dye/electrolyte interface greatly influences the photoelectron conversion efficiency. Hybrid semiconductor materials with matched band potentials are designed to reduce the charge recombination. In this study, SrTiO₃/TiO₂ hybridstructure was synthesized by using TiO₂ nanoparticles as template in a hydrothermal, showing a negative shift in the flat band potential. The DSSC with the SrTiO₃/TiO₂ anode exhibits an increased photovoltage and a reduced photocurrent. The suppression of charge recombination at the TiO₂/dye/electrolyte interface was observed in the electrochemical impedance spectroscopy, causing an improvement in the photovoltage. However, the SrTiO₃/TiO₂ system shows an obstructed electrons injection from the dye to SrTiO₃/TiO₂, limiting the photocurrent performance. The photoelectrochemical properties of the SrTiO₃/TiO₂ system are discussed in detail herein.     

Measuring internal electric fields in organic light-emitting diodes using electroabsorption spectroscopy

A widely applicable electroabsorption technique to measure internal electric fields in organic light-emitting diodes is presented. The technique exploits the change in the a.c. electroabsorption response in the presence of a d.c. electric field. The electroabsorption signal is modulated at the fundamental frequency of the a.c. test signal, in addition to the usual modulation at the second harmonic frequency, when a d.c. bias is present. In metal/organic film/metal devices employing different metal contacts there is a built-in electric field in the organic film caused by the difference in work function between the two contacts. The electroabsorption response at the fundamental frequency of the applied a.c. bias is measured as a function of an external d.c. bias. The electroabsorption signal is nulled when the applied d.c. bias cancels the built-in electric field established by the different metals. We apply this technique to measure changes in metal–polymer Schottky barrier heights as a function of the contact metal. In metal/multiple organic films/metal structures the electroabsorption signals from the constituent organic films are identified spectroscopically and measured at both the fundamental and second harmonic frequency of the a.c. test signal. The amplitudes of the electroabsorption responses are then used to determine the a.c. and d.c. electric fields present in the organic layers. We apply this technique to determine the d.c. electric field distribution within a multi-layer organic light-emitting diode. These results highlight the general applicability of electroabsorption methods to probe internal electric fields in organic light-emitting diodes. © 1997 John Wiley & Sons, Ltd.     

一种具有稳定发射光谱的高效率白色有机电致发光器件

报道一种具有稳定发射光谱的新型白色有机电致发光器件. 选择DCJTB 作为红光染料将其掺入空穴传输材料NPB 中作为空穴传输层和第一发光层, 提供蓝光和红光; 选择AlQ 作为电子注入敏化剂, 将其掺入NPB 中作为第二发光层, 提供蓝光和绿光. DCJTB和AlQ 的掺杂浓度分别被优化为0.4%和1.4%, 第二发光层的厚度被优化为3 nm. 最终,得到了纯白色发射的有机电致发光器件; 该器件启亮电压仅3.1 V, 最大亮度高达32749 cd/m², 器件的最大电流效率为8.67 cd/A, 器件的最大功率效率为8.78 lm/W. 而且, 空穴型主体材料的选择导致该器件的色稳定性非常理想. 随着电流密度的提高, 该器件的色坐标始终稳定在(0.343, 0.342)到(0.328, 0.336)的范围内.     

电荷注入检测器电感耦合等离子体光谱仪测定铂族元素的性能

研究了用电荷注入检测器等离子体光谱仪测定铂族元素的分析性能。结果表明铂族元素有较好的检出限和10^4以上的线性动态范围，铂族元素间光谱干扰很少，在元素浓度＞1mg/L时测量精度可优于1％，钠对铂族元素的影响是轻微的。     

Charge Carrier Dynamics in PDPP-F/PCBM Heterojunction Solar Cells

The morphology dependent of migration and recombination kinetics of charge carriers in the polymer solar cell based on poly {2,7'-9,9-dioctylfluorene-alt-5-diethylhexyl-3,6-bis(5-bromothiophen-2-yl)pyrrolo[3,4-c]-pyrrole-1,4-dione}(PDPP-F) was investigated with photo-induced charge carrier extraction by linearly increasing voltage technique. The recombination coefficient of charge carriers decreased and the mobility of charge carriers increased, after the mass ratio of[6,6]-phenyl-C61-butyric acid methyl ester(PCBM) increased from 3:2 to 2:1. Meanwhile, both of them were sensitive to the applied electric field and could be together responsible for the improvement of voltage performance of polymer solar cell.     

Alkali metal salts doped pluronic block polymers as electron injection/transport layers for high performance polymer light-emitting diodes

A series of alkali metal salts doped pluronic block copolymer F127 were used as electron injection/transport layers (ETLs) for polymer light-emitting diodes with poly[2-(4-(3′,7′-dimethyloctyloxy)-phenyl)-p-phenylenevinylene] (P-PPV) as the emission layer. It was found that the electron transport capability of F127 can be effectively enhanced by doping with alkali metal salts. By using Li2CO3 (15%) doped F127 as ETL, the resulting device exhibited improved performance with a maximum luminous efficiency (LE) of 13.59 cd/A and a maximum brightness of 5529 cd/m2, while the device with undoped F127 as ETL only showed a maximum LE of 8.78 cd/A and a maximum brightness of 2952 cd/m2. The effects of the doping concentration, cations and anions of the alkali metal salts on the performance of the resulting devices were investigated. It was found that most of the alkali metal salt dopants can dramatically enhance the electron transport capability of F127 ETL and the performance of the resulting devices was greatly improved.     

电荷注入检测器电感耦合等离子体光谱仪的稀土元素分析性能

研究了电荷注入检测器电感耦合等离子体发射光谱（ＣＩＤ－ＩＣＰＥＳ）测定稀土元素的分析性能。结果表明,在稀土元素常用谱线波段内（２６０～４４０ｎｍ）光谱背影发射强度低于４０ＣＰＳ（计数／秒）,ＲＳＤ〈０．６％。研究了谱线强度和相对标准偏差的关系,当谱线强度高于５ＣＰＳ时,对于任何稀土元素谱线的ＲＳＤ均低于０．６％。谱线强度降低时,ＲＳＤ逐渐增大。文中给出了稀土元素常用分析谱线的强度值、线背比、背影等     

电荷注入检测器电感耦合等离子体光谱仪测定碱金属的分析性能

研究了带有电荷注入检测器的等离子体光谱仪测定Li,Na,K的分析性能，测定了碱金属主要分析线的检出限，标准曲线的线性动态范围，元素间的相互影响，探讨了RSD与浓度的关系及Na对等离子体稳健性的影响。     

锌掺杂对TiO2染料敏化电池光阳极中电荷俘获态分布及电子复合过程的影响

基于瞬态光电压和瞬态光电流技术研究了锌掺杂的TiO2染料敏化太阳能电池中电子复合及传输的动力学行为.通过实验获得了不同阳极掺杂条件下的电子复合时间常数与电子收集时间常数,考察了锌掺杂对电池阳极材料导带能级和电子俘获态的影响.研究结果表明,锌的掺杂在提高TiO2导带能级的同时延长了俘获态电子的复合时间常数,从而大大提高了电池的开路电压.     

A novel fabrication technique and new conjugated polymers for multilayer polymer light-emitting diodes

We report a novel fabrication technique for multilayer light-emitting diodes composed of new polyoxadiazole, POD, conjugated polymers for the first time. The fabrication technique called vapor deposition polymerization is described. Chemical modification of monomers brought about the enhancement of reactivity and the production of high molecular weight of POD. Emission color with photoexcitation was controllable from violet-blue to green by varying the chemical structures of PODs. It was found that PODs could be employed as either electroluminescent or carrier-injecting layers by the optimization of the device structure. Two types of bilayer devices, which are constructed with POD/tris (8-quinolinoato) aluminum, Alq₃, and with two POD layers with different chemical structures, were investigated. Carrier injection begins in the POD/Alq₃ bilayer device near 7 V, and the device emitted green light from Alq₃. The maximum luminance of the POD/Alq₃ device reached 3500 cd/m². The POD/POD bilayer device emitted blue light with maximum luminance of 21 cd/m². Electroluminescence spectra of the devices coincided with photoluminescence spectra of each emitting material used. © 1997 John Wiley & Sons, Ltd.     

应用表面等离激元提高有机发光器件效率的研究进展

表面等离激元（SPP）存在于金属和介质界面,是光场和金属表面自由电子相互作用而产生的电子集体振荡行为.一方面,由于在金属纳米颗粒表面会形成局域的SPP震荡（LSP）,可以调控金属表面附近分子的发光性质,因此,很多研究者尝试在有机电致发光器件（OLED）中引入金属纳米颗粒,利用LSP改善OLED器件性能;另一方面,在传统发光器件中,由于金属表面等离激元的波矢量和自由光波的波矢量不匹配,无法辐射成自由光波,最终只能以热能的形式耗散掉.通过改变金属表面形貌,如附加光栅结构等方法,使得SPP的能量能够耦合成自由光,从而提高发光器件的外量子效率.利用SPP来提高有机发光器件的效率,已经引起广泛的关注,本文着重综述以下两个方面的工作：一是采用金属纳米颗粒的LSP提高荧光分子辐射跃迁的几率,从而提升发光器件的内量子效率;二是利用有序或无序光栅结构使得SPP与自由光的波矢匹配来提高器件的耦合出光,从而提升外量子效率.     

Dual functions of a novel low-gap polymer for near infra-red photovoltaics and light-emitting diodes

We have synthesised and characterised a new low-gap conjugated polymer, with a broad absorption profile. In blends with a C(70) derivative we demonstrate power conversion efficiencies of 0.76%. We show electroluminescence from the polymer peaking at 956 nm, and quantum efficiency of 0.02% in a blend.