Organic electroluminescent device based on electropolymerized polybithiophene as the hole-transport layer

An ultrathin film of polybithiophene (PBTh), used in organic electroluminescent (EL) devices, was generated by an electrochemical method with a conducting indium tin oxide (ITO) glass as the working electrode. The light-emitting layer could be deposited directly onto the PBTh by using spin coating for fabrication of the organic EL devices. It was found that the film of PBTh as the hole-transport layer for the EL device could effectively raise the EL intensity and efficiency. The EL intensity of the ITO/PBTh/emitting layer/Al device is about 100 times as strong as that of the ITO/emitting layer/Al device at the same current density of 50 mA/cm².     

SYNTHESIS AND CHARACTERIZATION OF PHENOTHIAZINE-BASED PPV-TYPE COPOLYMERS CONTAINING FLUORENE AND THIOPHENE MOIETIES

Copolymers of fluorene-co-phenothiazine (P1) and thiophene-co-phenothiazine (P2) were prepared respectively by Wittig reaction. The synthesis, photo-physical and electroluminescent properties of the resulting polymers were analyzed by FT-IR, GPC, 1H-NMR, UV-Vis, Photoluminescence (PL), Electroluminescence (EL) and Cyclic Voltammetry (CV). Their single layer devices with configuration of ITO/polymers/Ca/Al were studied. GPC results revealed the weight-average molecular weight (Mw) was 3.0×103 and 5.4×103, respectively. The device with a single layer structure of ITO/P1/Ca/Al emits green light with the maximum peak at 552nm. However,the device with a single layer structure of ITO/P2/Ca/Al emit red light with the maximum peak at 616nm.     

8-羟基喹啉镧两亲性配合物LB膜的双层电致发光器件

以具有不同层数的两亲配合物二[2-(N-十六烷基氨基甲酰基)-8-羟基喹啉]合镧[La(HQ)₂Cl]的LB膜为发光层,PBD为电子传输层,制备了双层结构的电致发光(EL)器件:ITO/LB膜/PBD/Al.器件产生黄绿色注入式发光.LB膜的层数和沉积压对器件的性能具有重要影响.在16V激发电压下,5,11和21层LB膜双层EL器件的电流密度分别为48,29和16.4mA/cm²,启亮电压阀值为7.5,8.5和9.5V.器件的亮度随电流密度和驱动电压的增加而增加.在相同偏压下,21层LB膜EL器件的亮度大于5和11层LB膜的器件.在25mN/m沉积的LB膜制备的EL器件具有较高的亮度(1219cd/m₂)和击穿电压.     

主链含电子传输型基团的可溶性PPV发光特性研究

经由Ｗｉｔｉｇ－Ｈｏｒｎｅｒ反应合成了一种可溶的ＰＰＶ主链含有电子传输基团的新型结构电子聚合物。该低聚物的Ｍｗ＝１０００、Ｔｄ＝２７０℃,可溶于氯仿和四氢呋喃。构造了最简单的三明治式电致发光器件ＩＴＯ／Ｏ－ＰＰＶ（８０ｎｍ）／Ａｌ,其电致发光和光致发光光谱基本一致。该器件与同样结构的ＰＰＶ相比其ＥＬ表现出在５０９ｎｍ处单一的宽峰,而ＰＰＶ的器件为５２０ｎｍ和５５０ｎｍ的双峰。另外由于主链上含有电子传输特性的二唑基团及聚合物材料的分子量较小,器件的量子效率达到０．１３％,是同样结构器件ＰＰＶ量子效率的五倍     

聚合物薄膜交流电致发光器件

We have demonstrated an electroluminescent (EL) device having the structure of ITO/PPV/Alq3:PVK/Al. This device could be driven by either forward bias or backward bias, and its EL originated from PPV layer.     

Effects of Langmuir-Blodgett Film as Hole Transport Layer on Organic Electroluminescent Device Performance

Three types of organic electroluminescence(EL) cells with organic material FY as the EL-emitting layer and a copper phthalocyanine (CuPc) as the hole transport layer which were sandwiched between indium/tinoxde(ITO) and aluminum electrode have been fabricated by vacuum-vapor and Langmuir-Blodgett (LB) deposition:(a) ITO/FY/Al;(b)ITO/CuPc/FY/Al;(c) ITO/CuPc(LB)/FY/Al. It was found for the first time that the cell with the LB film as the hole transport layer has the highest luminescent intensity at the same bias-voltage. These results are attributed to the order orientation of the CuPc molecule in the layer of LB film.     

可溶性聚合物电致发光材料PDHPV的合成及单、双层发光二极管器件的发光性能比较

可溶性聚合物电致发光材料ＰＤＨＰＶ的合成及单、双层发光二极管器件的发光性能比较李晨曦，尹春，黄文强，印寿根，张会旗，何炳林，郑军，华玉林（南开大学高分子化学研究所，天津，３０００７１）（天津理工学院材料物理研究所）关键词ＰＤＨＰＶ共轭聚合物；电致发光...     

Electroluminescence performances of 1,1-bis(4-(N,N-dimethylamino)phenyl)-2,3,4,5-tetraphenylsilole based polymers in three cathode architectures

A new silole monomer with two 4-(N,N-dimethylamino)phenyl substitutions on silicon atom as designed and synthesized.Three copolymers PF-N-HPS1,PF-N-HPS10 and PF-N-HPS20 were then obtained by copolymerizations of 2,7-fluorene derivatives with the silole monomer at feed ratios of 1%,10%,and 20%.Their UV-vis absorption,electrochemical,photoluminescent,and electroluminescent (EL) properties were investigated.PF-N-HPS possessed HOMO levels of 5.25-5.58 eV,and showed green emissions.Using PF-N-HPS as the emissive layer,three different polymer light-emitting diodes were fabricated as device A with ITO/PEDOT/PF-N-HPS/Al,device B with ITO/PEDOT/PF-N-HPS/Ba/Al,and device C with ITO/PEDOT/PF-N-HPS/TPBI/Ba/Al.For the device A,PF-N-HPS only showed very low EL efficiency of 0.06-0.33 cd/A,indicating that the Al cathode could not inject electron efficiently to the emissive polymers containing the 4-(N,N-dimethylamino)phenyl groups.For the device B,low work function Ba supplied better electron injections,and the EL efficiency could be improved to 0.85-1.44 cd/A.TPBI with a deep HOMO level of 6.2 eV could enhance electron transport and hole blocking.Thus modified recombinations and largely elevated EL efficiency of 4.56-7.96 cd/A were achieved for the device C.The separation of the emissive layer and metal cathode with the TPBI layer may also suppress exciton quenching at the cathode interface.     

一种含铽单体的合成及其电致发光研究

合成了一种具有聚合活性的含铽配合物单体(Tb(acac)~2(AA)phen),并用红外光谱、元素分析等进行表征。研制了结构为ITO/PVK/Tb(acac)~2(AA)phen/Alq^3/Al的电致发光器件并测定了它的电致发光谱、电流-电压特性、亮度-电压曲线等性能。该器件具有良好的整流特性,其电致发光显示了铽离子的绿光特征发射,并具有较好的单色性。同时,探讨了该器件的电致发光机理。     

Photoluminescence and Electroluminescence Properties of 2,5-Bis[2,2′-bis(5-phenyl)-1,3,4-oxadiazole] Thiophene(T-OXD)and T-OXD/Poly(9-vinylcarbazole) Blends

The photoluminescence(PL) and the electroluminescence(EL) properties of a novel organic compound, 2,5-bis(2,2′-bis(5-phenyl)-1,3,4-oxadiazole(T-OXD), were studied in chloroform and in a solid thin film. The PL and the EL properties of T-OXD/poly(9-vinylcarbazole)(PVK) blends were also studied, which contained various contents of T-OXD. The PL maximum emission peaks of T-OXD/PVK blends show gradual bathochromtic-shift with the increase of the T-OXD content. The EL spectra of T-OXD/PVK devices are similar to their PL spectra, and all the EL maximum emission peaks show bathochromtic-shift compared with the corresponding PL spectra, which is ascribed to the formation of electroplex. The turn-on voltages for ITO/T-OXD:PVK/Al devices decreased from 13.5 V of the device cotaining 0.1% T-OXD(mass fraction) to 5 V of the device containing 5% T-OXD, which suggests that T-OXD improves the energy level match between T-OXD and PVK and enhances the emission efficiency. The experimental results indicate that T-OXD can be used as a good electron transporting material.     

Synthesis,characterization, and application of light‐emitting copolyfluorenes slightly doped with distyrylbenzene derivatives

Copolyfluorenes PFG1～PFG4 slightly doped with 0.006–0.5 mol % of 2,5‐dihexyloxy‐1,4‐bis(2‐phenyl‐2‐cyanovinyl)benzene (green chromophore) were synthesized by the Suzuki coupling reaction to be evaluated as hosts for white‐light electroluminescent (EL) devices. Their optical, thermal and electrochemical properties were almost identical to those of polyfluorene ( PF ) due to minimal chromophore content. However, the electroluminescent (EL) spectra of the PFGn were very different from photoluminescence spectra in film state. Relative intensity of green emission (ca. 521 nm) in EL spectra are much stronger than those in PL spectra, which can be attributed to charges trapping in the chromophores due to its narrow band gap (E_g ≈ 2.56 eV). The performance of EL devices [ITO/PEDOT:PSS/polymer/Ca (50 nm)/Al (100 nm)] were improved with an increase in chromophore content. The PFG4 device revealed the best performance (6790 cd/m², 1.69 cd/A), and the PFG1 and PFG2 devices exhibited comparable intensity in blue and green emissions. Blend EL devices were fabricated by using the PFGn as the hosts and a red iridium complex [Ir(piq)₂(acac)] as dopant. By controlling the amount of the iridium complex, the white‐light emitting device was achieved with PFG2 , with maximum brightness and CIE coordinate being 4120 cd/m² and (0.31, 0.28), respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 149–160, 2009     

Optimization of high-performance blue organic light-emitting diodes containing tetraphenylsilane molecular glass materials

Molecular glass material (4-(5-(4-(diphenylamino)phenyl)-2-oxadiazolyl)phenyl)triphenylsilane (Ph(3)Si(PhTPAOXD)) was used as the blue light-emitting material in the fabrication of high-performance organic light-emitting diodes (OLEDs). In the optimization of performance, five types of OLEDs were constructed from Ph(3)Si(PhTPAOXD): device I, ITO/NPB/Ph(3)Si(PhTPAOXD)/Alq(3)/Mg:Ag, where NPB and Alq(3) are 1,4-bis(1-naphylphenylamino)biphenyl and tris(8-hydroxyquinoline)aluminum, respectively; device II, ITO/NPB/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag, where TPBI is 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene; device III, ITO/Ph(2)Si(Ph(NPA)(2))(2)/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag, where Ph(2)Si(Ph(NPA)(2))(2) is bis(3,5-bis(1-naphylphenylamino)phenyl)-diphenylsilane, a newly synthesized tetraphenylsilane-containing triarylamine as hole-transporting material; device IV, ITO/Ph(2)Si(Ph(NPA)(2))(2)/NPB/Ph(3)Si(PhTPAOXD)/TPBI/Mg:Ag; device V, ITO/CuPc/NPB /Ph(3)Si(PhTPAOXD)/Alq(3)/LiF/Al, where CuPc is Cu(II) phthalocyanine. Device performances, including blue color purity, electroluminescence (EL) intensity, current density, and efficiency, vary drastically by changing the device thickness (100-600 A of the light-emitting layer) and materials for hole-transporting layer (NPB and/or Ph(2)Si(Ph(NPA)(2))(2)) or electron-transporting material (Alq(3) or TPBI). One of the superior OLEDs is device IV, showing maximum EL near 19 000 cd/m(2) with relatively low current density of 674 mA/cm(2) (or near 3000 cd/m(2) at 100 mA/cm(2)) and high external quantum efficiency of 2.4% (1.1 lm/W or 3.1 cd/A). The device possesses good blue color purity with EL emission maximum (lambda(max)(EL)) at 460 nm, corresponding to (0.16, 0.18) of blue color chromaticity on CIE coordinates. In addition, the device is reasonably stable and sustains heating over 100 degrees C with no loss of luminance on the basis of the annealing data for device V. Formation of the exciplex at the interface of NPB and Ph(3)Si(PhTPAOXD) layers is verified by EL and photoluminescence (PL) spectra studies on the devices with a combination of different charge transporting materials. The EL due to the exciplex (lambda(max)(EL) at 490-510 nm) can be properly avoided by using a 200 A layer of Ph(3)Si(PhTPAOXD) in device I, which limits the charge-recombination zone away from the interface area.     

Synthesis,characterization, and optoelectronic properties of hyperbranched polyfluorenes containing pendant benzylether dendrons

Linear polyfluorenes with low generation of side benzylether dendrons ( PLG0 , PLG1 ) and hyperbranched polyfluorenes with 1,3,5‐benzene branch unit ( PHG0 and PHG1 ) were prepared by the Suzuki coupling reaction to investigate the structural effect on optoelectronic properties. Their optical properties, both in solution and film state, were investigated using absorption and photoluminescence (PL) spectra. The excimer emission of polyfluorene at about 530 nm, induced by thermal annealing, was completely suppressed by the hyperbranched structure, but the suppression was not obvious by the side benzylether dendrons. The optoelectronic performance of the EL devices (ITO/PEDOT:PSS/polymer/Ca/Al) was strongly dependent upon chemical structures of the emitting polyfluorenes. The hyperbranched PHG0 with zero generation of benzylether side groups revealed the best device performance, with maximal luminance and maximal luminance efficiency of 2350 cd/m² and 0.33 cd/A, respectively. The results suggest that incorporation of branch units with low generation of benzylether dendrons is an effective way to improve annealing stability and EL performance of the polyfluorenes. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 5945–5958, 2008     

主链含电子传输型团的可溶性PPV聚合物载流子传输特性研究

合成了一种聚苯撑乙烯撑(PPV)主链上含有电子传输基团的新型结构电子聚合物(O-PPV).该低聚物的M_w=1000,T_g=197℃,可溶于氯仿和四氢呋喃.单层O-PPV器件的发光效率约为单层PPV器件的5～8倍.进一步构造了结构为空穴传输特性材料/O-PPV和O-PPV/电子传输特性材料的双层器件来研究O-PPV的载流子传输特性,实验结果表明,O-PPV是一种具有明显两性载流子传输的特性材料.     

给体-受体-给体窄带隙染料掺杂聚芴发光二极管

合成了一系列给体-受体-给体型窄带隙荧光分子, 并将其作为掺杂剂与主体(Host)宽带隙聚芴共混制备发光二极管. 荧光分子为4,7-二呋喃-苯并噻二唑(O-S)、4,7-二噻吩-苯并噻二唑(S-S)、4,7-二(N-甲基吡咯)-苯并噻二唑(N-S)、4,7-二硒吩-苯并噻二唑(Se-S)和4,7-二(N-甲基吡咯)-苯并硒二唑(N-Se). 溶液中荧光分子的紫外-可见吸收峰位于447~472 nm, 荧光发射峰位于563~637 nm. 该系列荧光分子掺杂聚芴(PFO)发光器件的电致发光峰位于580~633 nm. 当器件结构为ITO/PEDOT/PVK/PFO+N-Se/Ba/Al时, 最大外量子效率为1.28%, 电流效率1.31 cd/A.     

Synthesis and characterization of polyfluorenes containing bisphenazine units

Novel conjugated copolymers based on 9,9‐dioctylfluorene and bisphenazine (BP) were synthesized by Suzuki polymerization. Energy transfer from the conjugated main chain to the BP moieties was observed. Full energy transfer was achieved when the molar content of the bisphenazine was 20% (20BPPF) in toluene solution. The similar phenomena were observed even for 1% bisphenazine content copolymer (1BPPF) in film. The lowest occupied molecular orbital (LUMO) energy levels (?3.06 eV) of the copolymers were lower than that of the polyfluorene homopolymer (PFO; ?2.65 eV), indicating that the introduction of the BP unit was benefit to electron injection. Single‐layer electroluminescent devices (ITO/PEDOT:PSS/polymer/LiF/Al) were fabricated to investigate their electroluminescence (EL) performances. The maximum brightness and current efficiency of all BPPF copolymers surpassed the PFO homopolymer. The best single‐layer device was based on 5BPPF, with a maximum brightness of 1532 cd/m² and current efficiency of 1.09 cd/A. Much higher efficiency could be achieved for multilayer EL devices of 5BPPF (ITO/PEDOT:PSS/PVK/polymer/TPBI/LiF/Al), which showed a maximum current efficiency of 10.01 cd/A. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1990–1999, 2010     

基于聚芳醚的双色白光聚合物的合成与光物理及电致发光性能

采用缩聚反应,通过将深蓝光荧光团(五联芴)和橙光荧光团(4-芴基-7-(4-二苯胺基-苯基)-2,1,3-苯并噻二唑)分别链接在聚芳醚的侧链上,合成了一种双色白光电致发光聚芳醚P1,接着将一种高效浅蓝光荧光团(2,7-二(9-乙基-咔唑乙烯基)芴)引入到了P1的侧链上,得到了聚芳醚P2和P3.系统研究了这些聚芳醚材料的溶解性、热稳定性、电化学性能、光物理性能和电致发光性能等.结果表明,所有聚芳醚都具有良好的溶解性与热稳定性;薄膜态时存在明显的由深蓝光荧光团到浅蓝光荧光团及橙光荧光团的能量转移;退火前后的薄膜光致发光光谱基本一致,表明具有优秀的光谱稳定性.基于这些聚芳醚的单层电致发光器件(ITO/PEDOT:PSS/高分子/Ca/Al),利用部分能量转移和电荷俘获作用,可以实现近白光发射.器件的最大电流效率可以达到7.96 cd/A,最大亮度为9950 cd/m2,色坐标为(0.33,0.44).     

NARROW BANDWIDTH BRIGHT SCARLET ORGANIC ELECTROLUMINESCENT DEVICE BASED ON N,N'-BIS[4-(N,N-DIMETHYLAMONO)-BENZYLIDENE]-DIAMINOMALEONITRILE DYE

A novel red dye, N, N'-bis[4-(N,N-dimethylamino)-benzylidene]diaminomaleonitrile (BAM), was prepared by reacting diaminomaleonitrile with 4-(N,N-dimethylamino)-benzaldehyde and were characterized by ¹H NMR, UV absorption and photoluminescence. The BAM dye showed an absorption peak wavelength of 530 nm and bright photoluminescence with a peak wavelength at 675 nm. It was used as the doped emitter for fabricating a bright scarlet organic electroluminescent (EL) device. The structure of the double-layer EL device consisted of a hole-transport layer and a luminescent layer between ITO glass and magnesium electrodes. The hole-transport layer was a poly(N-vinylcarbazole) (PVK) film. The luminescent layer consisted of a host material, 8-hydroxyquinoline aluminum (Alq₃), and BAM dye as the dopant. A bright light with the peak of 620 nm and narrow bandwidth of 50 nm was obtained in the device with a maximum luminance of 6230 cd/m². The emission spectra almost unchanged as the luminance increased with increasing injection current and the bias voltage. A tentative explanation from both the electronic distribution viewpoint and the molecular geometric analysis for the narrow bandwidth of this red dye was offered.     

Influence of Poly(methylmethacrylate) on 8-hydroxyquinoline Derivative-Metal Complexes Electroluminescence

A new method is presented of enhancing the organic electroluminescent(EL) efficiency by using poly (methylmethacrylaie) (PMMA) as barrier layers which play the role of controlling the electron-hole recombination in the organic EL materials. The organic EL device with one layer of 8-hydroxyquinoline derivalive-metal complexes-(Alq3, Znq2) as the EL-emitting layers, and two layers of EL emitting materials deposited on PMMA Langmuir-Blodgett films (PMMA/Alq3, PMMA/Znq2) sandwiched between indium/tin oxide (ITO) and aluminum electrodes have been fabricated, respectively. The evidence reveals that the LB film takes an importance to raising the 8-hydroxyquinoline derivative-metal complexes EL efficiency.     

导电聚合物有序超薄膜的合成及其作为有机电致发光器件空穴注入层

采用修饰多层LB膜的方法制备了导电聚合物聚-3,4-乙烯二氧噻吩/二十烷酸(PEDOT:AA)复合层状有序膜, 构筑了一种导电聚合物镶嵌的多层有序膜结构. 将这种导电聚合物有序薄膜沉积于ITO电极表面, 将其作为有机电致发光二极管(OLED)的空穴注入层, 并研究了ITO/(PEDOT:AA)/MEH-PPV/Al器件的性能. 研究结果表明, 与采用聚3,4-乙烯二氧噻吩/聚苯乙烯磺酸(PEDOT:PSS)自组装膜和旋涂膜作为空穴注入层的ITO/(PEDOT:PSS)/MEH-PPV/Al器件相比, 器件的发光效率增加, 起亮电压降低. 我们认为这是由于PEDOT:AA薄膜提供了一种有序层状结构后, 减小了ITO与MEH-PPV间的接触势垒, 改善了空穴载流子注入效率. 进一步的研究表明, 由于PEDOT:AA多层膜间靠较弱的亲水、疏水作用结合, 这种导电多层有序膜的热稳定性与普通LB膜相似, 在较高温度下发生从层状有序态到无序态的变化, 这是导致OLED器件性能发生劣化的主要原因.