Summary: We have designed and synthesized novel diphenylamine‐substituted phenylazomethine dendrimers (DP‐Gn, n = 1, 2) as hole‐transport materials for organic light‐emitting diodes (OLEDs). These dendrimers similar to phenylazomethine dendrimers showed a stepwise metal complexation with metal ions. They have good multi‐redox properties attributed to the terminal amine moieties and excellent thermal stabilities. Double layer EL devices utilizing the dendrimers as a hole‐transport material and Alq3 as the emitting and electron transport materials were fabricated. The EL performances of the devices increased with higher dendrimer generations. Moreover, by using the metal ion (0.5 equiv. SnCl2)‐complexed DP‐G2 dendrimers, the luminance and EL efficiency of the devices were drastically increased by more than double and over 30%, respectively. These metal complexable phenylazomethine dendrimers are novel and promising materials for highly efficient OLEDs.
Structure of the diphenylamine‐substituted phenylazomethine dendrimer DP‐G2. 相似文献
A new series of two poly(carbazole)‐based copolymers (poly(9‐hexyl‐carbazole‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PCVz) and poly(9,9‐dioctylfluorene‐co‐9‐(6‐(3‐(4‐phenylquinolin‐2‐yl)carbazol‐9‐yl)hexyl)carbazole) (PFCVz)) containing carbazoylphenylquinoline pendant groups were synthesized via the Suzuki coupling reaction for polymer light‐emitting diode applications. The electro‐optical properties of ITO/PEDOT/Polymer/PBD/LiF/Al devices based on these copolymers were investigated using UV‐visible, photoluminescence, and electroluminescence spectroscopy. The turn‐on voltages of the copolymer devices were found to be 6.0–8.0 V. The maximum brightness and luminescence efficiency of the copolymers device were found to be 230 cd · m?2 and 0.28 cd · A?1 at 11 V, respectively.
A series of highly air‐stable, low‐bandgap poly(3‐alkylthiophene)s containing electron‐rich thieno[3,2‐b]thiophene and electron‐deficient thiazolo[5,4‐d]thiazole rings were synthesized by the Stille coupling reaction. The polymers exhibited good thermal stability and solubility with excellent film forming properties when drop‐ or spin‐cast from solution. A strong absorption at 564–568 nm and a shoulder at 614–616 nm were observed. The optical bandgap of the polymers was found to be 1.82–1.85 eV. The IP of the polymers was found to be 5.62–5.65 eV. All polymers showed strong fluorescent emission both in solution and in the solid state. EL devices were fabricated using the polymers as an emissive layer and red emission was observed with the emission range of 649–679 nm.
Summary: A novel series of supramolecular polymers based on zinc‐salen chromophores were readily prepared via ligand‐metal coordination. These polymers were characterized by FT‐IR, NMR, GPC and elemental analysis. All the polymers were readily soluble in common organic solvents and had substantially good thermal properties. Cyclic voltammetry revealed they had LUMO energy levels ranging from −3.20 to −3.23 eV and HOMO energy levels ranging from −6.13 to −6.15 eV. The polymer films can emit strong green photoluminescence (PL) with relatively high quantum efficiencies of 42–51%. Light‐emitting diodes with the configuration ITO/PEDOT/polymer/BCP/Alq3/LiF/Al were efficient green emitters, with maximum current efficiencies of 0.9–2.3 cd · A−1. The preliminary EL results thus suggest that these polymers are potential candidates for efficient green emission in polymer LEDs.
The synthesis of two random copolymers bearing pendant mixed‐ligand orthometallated terpyridine‐based cationic iridium (III) complexes, as well as their uses as single‐layered electrophosphorescent emitters in polymer light‐emitting diodes is described. Both solution‐processable iridium metallopolymers are prepared by copolymerization of styrene with a complex‐substituted styrene by nitroxide mediated polymerization. Results on devices based on metallopolymers used as dopant of poly(N‐vinylcarbazole) or alone as single layers are presented.
Fluorene‐based single‐chain copolymers with a white light emitter consisting of a blue and an orange chromophore have been synthesized and their photophysical and electroluminescent properties are investigated. The experimental results suggest that only a relatively small fraction of the orange‐emitting units incorporated into the fluorene is needed to achieve efficient white light emission by controlled incomplete energy transfer. A device from a copolymer with 0.02% DDQ content showed the highest external quantum efficiency of 2.64% with a luminance efficiency of 4.06 cd · A?1 with CIE coordinates (0.28, 0.24). The EL emissions are extremely stable over a wide range of current densities.
Summary: Novel PPV derivatives (PCA8‐PV and PCA8‐MEHPV) containing N‐phenyl‐carbazole units on the backbone were successfully synthesized by the Wittig polycondensation of 3,6‐bisformyl‐N‐(4‐octyloxy‐phenyl)carbazole with the corresponding tributyl phosphonium salts in good yields. The newly formed and dominant trans vinylene double bonds were confirmed by FT‐IR and NMR spectroscopy. The polymers (with of 6 289 for PCA8‐PV and 7 387 for PCA8‐MEHPV) were soluble in common organic solvents and displayed high thermal stability (Tgs are 110.7 °C for PCA8‐PV and 92.2 °C for PCA8‐MEHPV, respectively) because of the incorporation of the N‐phenyl‐carbazole units. Cyclic voltammetry investigations (onsets: 0.8 V for PCA8‐PV and 0.7 V for PCA8‐MEHPV) suggested that the polymers possess enhanced hole injection/transport properties, which can be also attributed to the N‐phenyl‐carbazole units on the backbone. Both the single‐layer and the double‐layer light‐emitting diodes (LEDs) that used the polymers as the active layer emitted a greenish‐blue or bluish‐green light (the maximum emissions located 494 nm for PCA8‐PV and 507 nm for PCA8‐MEHPV, respectively). Compared with those of the single‐layer devices, the emission efficiencies of the double‐layer devices, in which an electron‐transporting layer (Alq3) was added, were enhanced by a factor of 10, implying that the better hole‐electron balance is achieved because of the incorporation of the electron‐transporting layer.
The N‐phenyl‐carbazole‐containing polymers synthesized. 相似文献
A new alternative copolymer composed of fluorene and quinoxaline units having benzothiadiazole groups in the side chain was prepared and used as a green emitter for polymeric light‐emitting diodes to give a device emitting pure green color at about 520 nm with a chromaticity coordinate of (x = 0.32, y = 0.59), matching the NTSC 1979 standard green color (x = 0.31, y = 0.595) very well.
A series of anthracene‐based conjugated copolymers containing 9,10‐bis(6‐bromonaphthalen‐2‐yl)‐2‐tert‐butylanthracene (BNA) and 2,7‐diphenyl substituted fluorene (DPPF) moieties are prepared via a palladium‐catalyzed Suzuki polymerization. All of the synthesized polymers emit blue light at around 450 nm and show good thermal and color stability. Their electroluminescence spectra remain unchanged at high driving voltage. The double‐layer polymer light‐emitting diode (PLED) fabricated with ITO/PEDOT:PSS/DPPFBNA3/CsF/Al, produces a maximum brightness of 1 650 cd · m?2 and has a luminance efficiency of 0.39 cd · A?1. The ITO/PEDOT:PSS/TFB/DPPFBNA3/CsF/Al multilayer PLED, incorporating a TFB layer to facilitate hole transportation, produces a maximum brightness of 5 371 cd · m?2 and a luminance efficiency of 1.18 cd · A?1.
New carbazole‐based copolymers, which contain various concentrations of 9‐alkyl‐3,6‐carbazole fragments in the main chain connected via alkylene spacers, have been synthesized by Ni(0)‐catalyzed Yamamoto‐type aryl‐aryl coupling reactions. Full characterization of the copolymer structure by NMR spectroscopy and elemental analysis is presented. These compounds represent amorphous materials of high thermal stability with glass transition temperatures of 151–162 °C and thermal decomposition starting at temperatures >390 °C. UV‐Vis absorption and photoluminescence emission of the copolymers confirmed that the effectively conjugated segment in the 3,6‐linked carbazole‐type copolymers is limited to dyads (dimeric units). However, copolymers with varying concentrations of the oligocarbazole chromophores demonstrate different charge injection and transport properties in multilayer light‐emitting diodes with the copolymers as the hole transport and Alq3 as the electroluminescent/electron transport layer. The device based on a copolymer composed of oligocarbazole blocks with an average length of around four carbazoles exhibited the best overall performance with a turn‐on voltage of 3.5 V, a maximal photometric efficiency of 4.1 cd · A?1 and maximum brightness of about 4 200 cd · m?2.
Phenothiazine alternating copolymer poly{4,8‐bis(5‐dodecylthiophene‐2‐yl)benzo[1,2‐b:4,5‐b′]dithiophene‐alt‐(10‐decylphenothiazine)} ( P1 ) is synthesized by Stille coupling polymerization. The synthesized polymer has an electrochemical bandgap of 1.61 eV and displays good photoluminescence with a quantum yield of 63.3%. The polymer is tested as a light‐emitting material in polymeric light‐emitting diodes (PLEDs) with a device structure of indium tin oxide (ITO)/poly(3,4‐ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS)/polymer/Cs2CO3/Al. The devices display an orange‐yellow electroluminescence (Commission Internationale de l'Eclairage (CIE) 1931 color‐space chromaticity diagram: x = 0.5355 and y = 0.4611) with a maximum brightness of 3130 cd m?2 at an applied voltage of 10 V. 相似文献
Summary: A monomer M as well as a poly(methacrylate) P carrying the same chromophore, that consists of 1,3,4‐oxadiazole and stilbene units, were efficiently synthesized. They dissolved in common organic solvents such as THF, chloroform, dichloromethane, 1,1,2,2‐tetrachloroethane and chlorobenzene. P showed a Tg value of 145 °C. Both M and P were stable up to approximately 300 °C and afforded anaerobic char yield of about 40% at 800 °C. Their optical properties were comparable. They emitted intense violet‐blue light in THF solution with a PL maximum at 413 nm and a PL quantum yield of 0.29 for M and 0.73 for P . Thin films of them displayed optical band gap of 3.03 eV and blue‐light emission with a PL maximum around 440 nm. The PL curves of both samples were progressively red‐shifted with increasing the solvent polarity. The influence of the annealing on the PL emission spectrum of M and P thin films was investigated.
Summary: Alkoxy substituted derivatives of poly‐ and oligo[(m‐phenylenevinylene)‐alt‐(p‐phenylenevinylene)] were synthesized via the Wittig ( P1 , OPV1 , OPV2 ) and the Wittig‐Horner ( P2 , OPV3 , OPV4 ) condensation routes. The polymers were characterized by 13C NMR, 1H NMR, FT‐IR spectroscopy and GPC. 1H NMR was a convenient tool to distinguish between the cis and trans double bonds in the compounds. Poly[(4‐decyloxy‐1,3‐phenylenevinylene)‐alt‐(1,4‐phenylenevinylene)] ( P1 ) contained cis and trans double bonds in significant amounts, the vinylene configuration of poly[(4‐decyloxy‐1,3‐phenylenevinylene)‐alt‐(2,5‐dipentyloxy‐1,4‐phenylenevinylene)] ( P2 ) was nearly exclusively trans. Model compounds ( OPV1–4 ) were also synthesized to support the structural and optical characterization. UV‐vis absorption, photoluminescence (PL) and cyclic voltammetry measurements have been performed to investigate the influence of the positions and the number of substituents on electronic levels. The polymers exhibited an intensive solid‐state emission in the blue‐green ( P1 ) and the green ( P2 ) region of the spectrum. Light emitting diodes have been fabricated consisting of ITO, PEDOT:PSS, P2 and Ca/Al. They exhibited high luminance of 100 cd · m?2 at 5.9 V and low onset voltages (4.3 V) for the electroluminescence (EL).
Schematic representation of a light emitting diode fabricated by use of an alkoxy substituted derivative of poly[(m‐phenylenevinylene)‐alt‐(p‐phenylenevinylene)] ( P2 ). 相似文献
A series of electrophosphorescent fluorene‐alt‐carbazole copolymers are synthesized by Suzuki polycondensation. A β‐diketone‐terminated alkyl chain grafted to the N‐position of carbazole serves as a ligand to form a pendant cyclometalated Ir complex with 10‐methyl‐dibenzo[a,c]phenazine (Mpq), 2,3‐diphenylquinoxaline (Bpq), and 1‐(benzo[b]thiophen‐2‐yl)isoquinoline (Biq), respectively. The emission of the device of PFCzIrBiq peaked at 715 and 790 nm, which is among the deepest red emissions reported so far. The well‐achieved device performances could be attributed to a combination of a higher triplet energy and suitable HOMO/LUMO energy levels which can assure efficient charge injection as a result of the incorporation of a 3,6‐carbazole unit into a polyfluorene backbone.
Summary: Soluble conjugated random and alternating copolymers (PCz‐PSP) derived from N‐hexyl‐3,6‐carbazole (Cz) and 1,1‐dimethyl‐2,3,4,5‐tetraphenylsilole (PSP) were synthesized by palladium(0)‐catalyzed Suzuki coupling reactions. The feed ratios of Cz to PSP were 95:5, 90:10, 80:20, 70:30, and 50:50. Chemical structures and optoelectronic properties of the copolymers were characterized by 1H NMR, 13C NMR, UV absorption, cyclic voltammetry, photoluminescence, electroluminescence, and field effect transistor. HOMO levels of the copolymers are between −5.15 and −5.34 eV. Single‐layer devices with a configuration of ITO/copolymer/Ba/Al were fabricated and the copolymer with PSP content of 20% displayed the highest external quantum efficiency of 0.77%. Field effect transistors with tantalum pentoxide‐polyacrylonitrile double insulators demonstrated that hole mobilities of the copolymers decreased with their PSP contents, and the hole mobility up to 9.3 × 10−6 cm2 · (V · s)−1 could be achieved.
Synthesis of coplymers derived from 3,6‐carbazole and silole. 相似文献
Summary: We report the thermal, optical, electrochemical and electroluminescent properties of four polymers P1 – P4 consisting of hole‐transporting [1,4‐bis(hexyloxy)‐2,5‐distyrylbenzene;DSB] and electron‐transporting [4‐(4‐(hexyloxy)phenyl)‐3,5‐diphenyl‐4H‐1,2,4‐triazole; TAZ] fluorophores linked by four kinds of connectors: (1) ether spacers, (2) single bonds, (3) 1,4‐phenylenes, and (4) 1,4‐divinylbenzenes. These polymers are soluble in common organic solvents such as chloroform, N‐methylpyrrolidone (NMP) and CH2Cl2CH2Cl2 and exhibit good thermal stability with decomposition temperatures higher than 340 °C. Compounds M1 – M3 containing a TAZ or DSB core were employed as a model to study the optical properties of the polymers. The photoluminescence (PL) spectral maxima of P1 – P4 in CHCl3 were spread over a wide range, from 453 nm to 501 nm, depending upon the chemical structures of the connectors. In the film state, the PL maxima shifted bathochromically from 464nm to 538 nm, which can be attributed to the formation of excimers. From the optimized semiempirical modified neglect of diatomic overlap (MNDO) calculations, the adjacent benzene rings between DSB and TAZ chromophores in P2 and P3 twist about 81–89° which is significantly different from P4 (circa 0°). The effect of the twisted connector architectures on optical and electrochemical properties for P1 – P4 is discussed. The electroluminescences of P1 – P4 and corresponding Commission Internationale de l'Eclairage (C.I.E.) coordinates are also depicted to indicate that incorporating different connectors to these polymers changed their color from blue, to green, to the yellow region.
The C.I.E. 1931 diagram of lights emitted from the PLED devices (ITO/PEDOT:PSS/ P1 – P4 /Al). 相似文献
Polyfluorenes are a class of promising blue light‐emitting conjugated polymer due to their excellent optoelectronic properties. However, the applications of polyfluorenes in polymer light‐emitting diodes (PLEDs) have been hampered by the appearance of long‐wavelength green emission, leading to the problem of color purity and stability. Hence, the preparation of pure blue‐emitting polyfluorenes becomes very important for the realization of real blue‐emitting PLEDs. In this short review, we introduce the efforts made by our group to realize polyfluorenes with pure blue emission, including the incorporation of spirobifluorene units, heterofluorene units, hyperbranched, and star‐shaped structures into polymer backbones.
Summary: A well defined blue electroluminescent fluorene‐carbazol‐fluorene trimer 3,6‐bis‐(9,9‐dihexyl‐9H‐fluoren‐3‐yl)‐9‐alkyl‐9H‐carbazole was synthesized using a Suzuki type cross coupling reaction as the key step. A way to attach this chromophore to a norbornene was developed and the resulting electroactive monomer was polymerised using the “3rd generation Grubbs catalyst” (N,N‐bis(mesityl) 4,5‐dihydroimidazol‐2‐ylidene)(3‐bromo‐pyridine)2(Cl)2Ru?CHPh), yielding an amorphous polymer with a narrow molecular weight distribution, which was used to build a light‐emitting diode exhibiting electroluminescence peaking at 410 nm.
Incorporation of the fluorene‐carbazol‐fluorene trimer as the emissive layer in an ITO/PEDOT:PSS/emitter/Ca/Al light emitting device. 相似文献
Summary: Novel readily soluble random low‐band‐gap conjugated copolymers (PFO–DTTP, Eg ≈ 1.77–2.00 eV) derived from 9,9‐dioctylfluorene (DOF) and 2,3‐dimethyl‐5,7‐dithien‐2‐yl‐thieno[3,4‐b]pyrazine (DTTP) were prepared. The solutions and the solid thin films of the copolymers absorbed light from 300–690 nm. Prototype photovoltaic cells from solid state composite films with the copolymer PFO–DTTP30 and [6,6]‐phenyl C61 butyric acid methyl ester (PCBM) showed power conversion efficiencies up to 0.83% under an AM1.5 solar simulator (100 mW · cm−2). For electroluminescent devices, the emission peaks were around 734–780 nm. This indicates that the low band gap copolymers are promising materials for polymeric solar cells and deep red/near infrared light‐emitting diodes.
Synthesis of novel low‐band‐gap fluorene‐based copolymer. 相似文献
A novel nitrogen‐containing electroluminescent copolymer, PQV‐alt‐MOPPV has been designed and synthesized by Wittig‐Horner polymerization. Structure, thermal stability, and optical and electrochemical properties of the resulting copolymer were characterized by FT‐IR, 1H NMR, elemental analysis, GPC, DSC, TGA, UV‐vis, PL, EL, and CV. The copolymer possesses excellent solubility in common organic solvents and good thermal stability. The absorption maxima of the copolymer in solution and a thin film are 490 and 516 nm, and the photoluminescence maxima in solution and thin film are 571 and 629 nm, respectively. The PLED (ITO/PEDOT: PSS (40 nm)/PQV‐alt‐MOPPV (80 nm)/Ca (30 nm)/Al (150 nm) shows a very pure red light emission with maximum peaks around 618 nm.
