8－羟基喹啉铝掺杂聚乙烯基咔唑薄膜的光致发光及电致发光

８－羟基喹啉铝掺杂聚乙烯基咔唑薄膜的光致发光及电致发光马於光,唐建国,沈家骢,刘式墉（吉林大学分子光谱与分子结构开放实验室,集成光电子学国家联合重点实验室,长春,１３００２３）关键词聚合物,光致发光,电致发光,８－羟基喹啉铝某些有机染料作为波长转换介...     

Electroluminescent Properties of an Electrochemically Cross‐Linkable Carbazole Peripheral Poly(Benzyl Ether) Dendrimer

The electroluminescent (EL) properties of a cross‐linkable carbazole‐terminated poly(benzyl ether) dendrimer, G₃‐cbz DN, doped into a PVK:PBD host matrix with a double‐layer device configuration are investigated. Different concentrations of the guest material can control device efficiency, related to chromaticity of white emission and the origin of excited‐state complexes occurring between hole‐transporting carbazole units (PVK or G₃‐cbz DN) and electron‐transporting oxadiazole (PBD). Two excited states (exciplex and electroplex) generated at the interfaces of PVK/G₃‐cbz DN and PBD result in competitive emission, exhibiting a broad band in the EL spectra.     

White light emission from single layer poly (n-vinylcarbazole) polymeric light-emitting devices by mixing singlet and triplet excimer emissions

White light electroluminescence (EL) was obtained by mixing emission from singlet and triplet excimers from a single poly (n-vinylcarbazole) (PVK) spin cast layer after irradiation of the solution with UV light. With increased UV light irradiation, the intensity from the triplet excimer (red-630 nm) of PVK increased compared with that of the singlet excimer (blue-460 nm) due to an increased population of both adjacent benzene rings being aligned with one another (fully overlapping) versus only one of the adjacent benzene rings being aligned (partially overlapping). The emission color changed from blue to white with increased UV irradiation time while the EL brightness and current density decreased and the turn-on voltage increased.     

Electroplex emission from a blend of poly(N-vinylcarbazole) and 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline

The PL and EL spectra of poly(N-vinylcarbazole) (PVK) : 2,9-dimethyl-4,7-diphenyl-1, 10-phenanthroline (BCP) (1:1 w/w) film were found completely different. The PL spectrum is a single peak at 415 nm that originates from excitons emission from PVK, and the tail of the spectrum is suggested to be excimer emission from BCP molecules. However, a new emission at 595 nm was found in the EL spectra of devices ITO/PEDOT:PSS(50 nm)/PVK:BCP(1:1)(100 nm)/Al. After aggregate, exciplex and product of electrochemical reaction were ruled out, the new emission was proposed to be electroplex emission that occurred between PVK and BCP molecules. Under high voltage, only electroplex emission can be observed in the EL spectra.     

Electroluminescence of poly(N-vinylcarbazole) films: fluorescence, phosphorescence and electromers

We have studied the electroluminescence (EL) properties of pure poly(N-vinylcarbazole) (PVK) films. Three types of light emission in the EL spectrum were observed, attributed to fluorescence, phosphorescence and electromers, respectively. The observation of electrophosphorescence from PVK films at room temperature is very meaningful, indicating that PVK can produce a large number of triplet excitons under an electric field at room temperature. Our results demonstrate clearly the reason why PVK is an excellent host material for phosphorescent polymer light-emitting diodes (PLEDs).     

Organic electroluminescent devices using europium complex‐doped poly(N‐vinylcarbazole)

Electroluminescence (EL) properties of europium (Eu) complex‐doped poly(N‐vinylcarbazole) (PVK) were investigated. A device structure of glass substrate/indium‐tin oxide/hole‐injection layer/Eu complex‐doped PVK/hole‐blocking layer/electron transport layer/electron‐injection layer/Al was employed. Red emission originating from Eu complex was observed. Relatively high luminance of 50 cd/m² and an efficiency of 0.2% were obtained. Copyright © 2004 John Wiley & Sons, Ltd.     

MULTILAYER ORGANIC LEDS BASED ON A NEW DYE-DOPED POLYMER*

A blue dye, l-benzothiazoly-3-phenyl-pyrazoline (BTPP) was found to function as bright lightemitting dye in organic electroluminescent devices. This heterocyclic compound exhibits good characteristicsof blue photoluminescence and electroluminescence, which has emission peak at 445 nm.The thin films offluorescent dye dispersed in poly(N-vinylcarbazole) (PVK) could serve as light-emitting layers in multilayerorganic LEDs. 2-(4-Biphenyl)-5-(4-tert-butylpheynyl)-1,3,4-oxadiazole (PBD) and tris-(8-hydroxyquinoline)aluminum (Alq3) were introduced into double-layer and three-layer devices respectively. The introduction ofelectron transport material Alq_3 enhanced the electron injection and luminous efficiency, as compared withdouble-layer devices. Maximum brightness and luminous efficiency can be reached up to 190 cd/m~2 and0.31 m/W, respectively.     

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.     

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。     

稀土配合物Eu(DBM)3为发光体的有机电致发光器件

分别以稀土配合物为发光中心，以PPV、Alq3为空穴输送层和电子输送层制备了结构为ITO／PPV／PVK：PBD：Eu（DBM）3／Alq3／Al的电致发光器件，其中发射层由旋涂法形成，该器件的最大亮度为52cd·m－2，且具有很好的单色性。     

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.     

PVK与新型D-π-A分子掺杂体系的能量转移及发光性质

通过对PVK与4种新型D-π-A分子(分别简写为CKD, TKD, PKD, NKD)掺杂体系的吸收光谱、激发光谱和光致发光光谱的研究, 分析了掺杂体系的光致发光特性和能量转移现象. 制备了结构为ITO/PEDOT/PVK∶D-π-A ω/Alq3/Al的电致发光器件, 研究了掺杂体系的电致发光性能. 研究结果表明, 通过改变D-π-A分子中不同给电子能力的电子给体, 可以调控其带隙, 进而实现对D-π-A分子发光峰位的调节; 给电子基团空间立构效应越高, 其荧光量子效率越高. 在掺杂体系的光致发光和电致发光中, PVK与D-π-A分子之间都发生了有效的能量转移, 通过调节PVK与D-π-A分子的比例, 可以调节掺杂体系的发光性能. 当TKD在PVK中的掺杂质量分数为6％时, 电致发光器件发光亮度为729.1 cd/m2时, 发光效率达到1.75 cd/A.     

The Anomalous Emission Characteristics of the Cyalume Fluorescer: 9,10-Bis (Phenylethynyl) Anthracene

A fancy emission behavior was found in the light carrier of the commercial Cyalume light stick, 9,10-bis (phenylethynyl) anthracene (BPEA). The yellowish-orange emission is noted from BPEA in methylcyclohexane matrix. Nitrogen laser time-resolved spectroscopy and excitation luminescene studies of BPEA in methylcyclohexane showed that the different emission behavior is probably due to the different conformation of the ground state of the BPEA in solid and in solution.     

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.     

Photoluminescence and electroluminescence of methoxy and carboethoxy derivatives of 1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline

A series of methoxy (MO) and carboethoxy (CE) derivatives of 1,3-diphenyl-1H-pyrazolo[3,4-b]quinoline ([DPPQ]) are characterized by spectroscopic methods. All dyes show the photoluminescent spectra which are highly solvatochromic. In the case of 6MO[DPPQ] and 6CE[DPPQ] the emission bands are broad and shifted to the red with increasing of solvent polarity whereas the dyes 6MO1pMO[DPPQ] and 6MO13pMO[DPPQ] exhibit a reverse solvatochromism. The large difference between the excited- and state-dipole moments indicates a strong electron transfer effects in all dyes. The EL spectra are obtained for the fabricated OLEDs with a general structure of EL device ITO/PVK:6X[DPPQ]/Ca/Al. The blue emission originating from PVK host matrix appears to be quenched in EL spectra of doped PVK matrix giving rise to emission in blue, blue-green or green spectral regions. The obtained results demonstrate that a series of newly synthesized methoxy and carboethoxy [DPPQ]-derivatives may be considered as promising materials for electroluminescent applications.     

ToF-SIMS imaging of the nanoscale phase separation in polymeric light emitting diodes: effect of nanostructure on device efficiency

The nanostructure of the light emissive layer (EL) of polymer light emitting diodes (PLEDs) was investigated using force modulation microscopy (FMM) and scanning time-of-flight secondary ion mass spectrometry (ToF-SIMS) excited with focused Bi(3)(2+) primary beam. Three-dimensional nanostructures were reconstructed from high resolution ToF-SIMS images acquired with different C(60)(+) sputtering times. The observed nanostructure is related to the efficiency of the PLED. In poly(9-vinyl-carbazole) (PVK) based EL, a high processing temperature (60 °C) yielded less nanoscale phase separation than a low processing temperature (30 °C). This nanostructure can be further suppressed by replacing the host polymer with poly[oxy(3-(9H-9-carbazol-9-ilmethyl-2-methyltrimethylene)] (SL74) and poly[3-(carbazol-9-ylmethyl)-3-methyloxetane] (RS12), which have similar chemical structures and energy levels as PVK. The device efficiency increases when the phase separation inside the EL is suppressed. While the spontaneous formation of a bicontinuous nanostructure inside the active layer is known to provide a path for charge carrier transportation and to be the key to highly efficient polymeric solar cells, these nanostructures are less efficient for trapping the carrier inside the EL and thus lower the power conversion efficiency of the PLED devices.     

Theoretical study on phosphorescence efficiency and color tuning from orange to blue-green of Ir(III) complexes based on substituted 2-phenylimidazo[1,2-a]pyridine ligand

The geometrical structures, phosphorescence quantum yields, and electroluminescence (EL) efficiency of six iridium(III) complexes containing 2-phenylimidazo[1,2-a]pyridine ligand are investigated by density functional theory (DFT), which show a wide color tuning of photoluminescence from orange (λ(em) = 550 nm) to blue-green (λ(em) = 490 nm). The calculated results shed some light on the reasons of the remarkably manipulated excited-state and EL properties through substitution effect. The Mulliken charge calculation reveals that attached -CF(3) groups on phenyl and imidazo[1,2-a]pyridine (impy) moieties (4) can make both of them as electron-deficient region, which will lead to the contraction of the whole coordination sphere and strengthen the metal-ligand interaction. While attaching two -CF(3) groups on phenyl ring can make it more electron-deficient, which will induce electron transferring from acac and impy fragment to phenyl ring, and also result in the contracted structure. The largest metal-to-ligand charge transfer ((3)MLCT) character and the smaller S(1)-T(1) energy gap (ΔE(S(1)-T(1))) value increase the emission quantum yields of 4 and 6 than other complexes. For EL efficiency, because of the similar highest occupied molecular orbital (HOMO) levels of 4 and 6 to that of holes injection material poly(N-vinylcarbazole) (PVK) and the larger dipole moments, majority hole will be accumulated on the HOMO of 4 and 6. Combination with the lower lowest unoccupied molecular orbital energy levels compared with PVK, the recombination zones of 4 and 6 can be well confined within emitting material layer (EML) and lead to the higher EL efficiency.     

PROBE FOR THE FORMATION RATIO BETWEEN EXCITED TRIPLETS AND SINGLETS AS GENERATED IN POLYMER LIGHT-EMITTING DIODES*

The electroluminescence (EL) produced by a highly luminescent phosphorescent dye Cu_4(C≡CPh)_4L_2 (L = 1.8-bis(di-phenylphosphino)-3, 6-dioxaoctane, Cu_4) doped polymer as emitting layer is reported. The effects o f the chargeinjection balance on the polymers, in particular, poly(N-vinylcarbazole) (PVK) have been studied by usingphotoluminescence and elecholuminescence spectroscopy. Changes in the emission spectra demonstrate the influence of thecharge injection balance on the formation ratio of triplet and singlet excitons. (This provides a new technical approach torealize the color patterning in polymer LEDs.     

Synthesis and characterization of light‐emitting oligo(p‐phenylene‐vinylene)s and polymeric derivatives containing three‐ and five‐conjugated phenylene rings. II. Electro‐optical properties and optimization of PLED performance

A series of multilayer polymeric light‐emitting diodes (PLEDs) containing an electron‐transporting layer (ETL), that is tris(8‐quinolinolato)‐aluminum(III) (Alq) and 2,2′,2″‐(1,3,5‐phenylene)‐tris[1‐phenyl‐1H‐benzimidazole] (TPBI), were fabricated by doping fluorescent oligo(p‐phenylene‐vinylene)s (BIII and BV) and polymer derivatives (PBV) into poly(N‐vinyl carbazole) (PVK). These PLEDs can be optimized by the design of multilayer device configurations (brightness increased 8–15 times by addition of ETL) and possess greenish electroluminescent (EL) spectra peaked about 500–540 nm. A remarkably high brightness of 56,935 cd/m² with a power efficiency of 3.25 lm/W was obtained in the device of PVK:BVOC₈‐OC₈ (100:20)/Alq (60 nm/60 nm). It suggests that the emission mechanism (including the conjugated and excimer emissions of BVOC₈‐OC₈ emitters) originates from both of BVOC₈‐OC₈ and ETL (Alq and TPBI) by varying the concentration of chromophores and adjusting the thickness of ETL. The concentration effect of the emitters in PVK (i.e. PVK:BVOC₈‐OC₈ = 100:5, 100:20, and 100:100 wt %) and the influence of the ETL (including its thickness) on the EL characteristics are also reported. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2922–2936, 2006     

氟取代三(8-羟基喹啉)铝衍生物电子结构、电子光谱的量子化学研究: 实现蓝色发光的途径

采用Gaussian 03程序包和密度泛函理论(DFT)B3LYP/6-31G方法, 研究了三(8-羟基喹啉)铝(Alq3)的3种氟代衍生物的电子结构与电子光谱, 讨论了氟原子在不同位置取代对Alq3的前线轨道、HOMO-LUMO能隙以及电子光谱的影响, 发现氟取代使Alq3的前线轨道能级降低, 在6位碳上氟代的Alq3的HOMO-LUMO能隙变大, 吸收和发射光谱发生蓝移, 而在5和7位碳上氟代的Alq3能隙变小, 吸收和发射光谱发生红移. 理论模拟结果与实验事实基本吻合, 证明在Alq3分子的合适位置进行化学修饰可实现蓝色发光.