Search

Two bipolar hosts, 8-cbzBIFP and 10-cbzBIFP, both with basic skeletons of orthogonally-connected carbazole and benzimidazo〈1,2-f〉phenanthridine (BIFP) have been prepared. The planar structure of the BIFP moiety governs the molecular stacking in the crystal lattice. Electron transport properties, in comparison to the benzimidazole derivatives, are facilitated. Both hosts display fabulous performances in phosphorescent organic light-emitting diodes with bis(2-phenylpyridine)(acetylacetonate)iridium(III) as an emitter. The optimized green PhOLED of 10-cbzBIFP achieves the maximum brightness (Lmax) of 58 810 cd m−2, the maximum current efficiency (ηc) of 87.0 cd A−1 and external quantum efficiency (EQE) of 21.1%. Likewise, 8-cbzBIFP shows an Lmax of 58 870 cd m−2, ηc of 77.3 cd A−1 and EQE of 19.1%.

This work reports on the facile synthesis, characterization, and electroactivity of a zinc-based [Zn3(TTPA)2(DHTP)3]·2DMF (1, TTPA = tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine, DHTP = dihydroxylterepthate) metal-organic framework, which has multifunctional properties due to its electroactive framework, permanent porosity, robust structure, and fluorescent nature. Topology analyses indicate that 1 contains a 3,4,4-c net. Sorption studies indicate that 1 is a suitable adsorbent for CO2 with a capacity of 10.2 wt % at 298 K; the capacity increased to 16.7 wt % at a lower temperature, 273 K. The incorporation of the redox-active TTPA ligand as an electron donor renders 1 to be an electroactive framework. The generation of radical cations from the chemical oxidation of 1 resulted in fluorescent quenching. The combination of porosity, fluorescence, and electroactivity in one entity suggests that 1 could serve as a sensing material for the detection of nitrobenzene. Exposing nitrobenzene to 1 quenches the fluorescent via host-guest interactions. The detection site of nitrobenzene in framework 1 was confirmed by single-crystal X-ray diffraction, [Zn3(TTPA)2(DHTP)3]·(H2O)(DMF)(2NB) or 1 ⊂ NB. In addition, the inclusion of nitrobenzene into the framework 1 stabilized the disordered molecules via strong hydrogen bonding. These findings indicate that versatile MOFs with multifunctional properties can be realized via a systematic design.

The efficient conversion of electron-hole (e-h) pairs into triplet excitons is a challenge for blue organic light-emitting diodes (OLEDs) based on triplet–triplet annihilation upconversion (TTAUC). The 25% fraction of e-h pairs that create singlet excitons represents a significant loss channel that can lead to parasitic red-shifted emission. In this study, an intermolecular intersystem crossing that relies on a “dark sensitizer” (DS) layer consisting of tris-(8-hydroxyquinoline)aluminum (Alq3) doped with tris[2-phenylpyridinato-C2,N]Iridium(III) (Ir(ppy)3) is demonstrated to enhance the TTAUC process. Carriers recombination and excitons generation are formed on Alq3 molecules. Alq3 singlet excitons are then quenched by the Ir(ppy)3 triplet state, followed by energy transfer to the Alq3 triplet state. The non-emissive, long-lived Alq3 triplets migrate from the sensitizer layer to an emitter layer where they undergo TTAUC to give blue fluorescence emission. This DS-TTAUC process promises no green emission from the Alq3. The efficiency of a blue OLED utilizing DS-TTAUC was improved by 34.2% compared to a standard TTAUC OLED. In addition, the device exhibited CIE coordinates of (0.15, 0.09). Furthermore, a high photoluminescence quantum yield fluorescence emitter is incorporated to enhance the singlet exciton emission in the emitter layer. A maximum external quantum efficiency of 7.54% can be achieved with recorded-high quantum yield of the TTAUC (ΦTTAUC) = 37.6% in solid state.

This work describes the successful incorporation of a redox active linker, tris(4-(1H-1,2,4-triazol-1-yl)phenyl)amine (TTPA) into Mn(II)/Cu(II) based coordination frameworks. Solution state in situ spectroelectrochemistry of EPR and UV/Vis/NIR of the TTPA ligand were measured to gain a deeper understanding of the charge delocalization of the triphenylamine backbone. The assignments of the absorption bands for the radical cations in UV/Vis/NIR spectroelectrochemistry were supported by DFT calculations. For Mn(II)/Cu(II) based coordination frameworks, solid state electrochemical and in situ spectroelectrochemical methods were applied to elucidate the accessible redox states and the optical properties of the frameworks. The findings provide a basic comprehension of the interconversion of different redox states and how an electroactive framework can be potentially used in applications of electrochromic and optical devices.

Organic light emitting diode (OLED) has lots of advantages in display technology such as self-emissive, light-weight, and compatible for flexible substrates. Compared to the red and green OLEDs, blue one has shorter lifetime due to high-energy polaron quenching. Triplet-triplet annihilation up conversion (TTAUC) is a promising way to reduce the driving voltage and improve the operation lifetime for a blue OLED. This system includes two materials, sensitizer and emitter, which has a narrower bandgap and triplet-triplet annihilation (TTA) characteristic, respectively. When the sensitizer is excited, its triplet exciton can transfer the energy to the triplet of emitter with lower triplet energy and fuse into one singlet exciton with a higher energy photon than the sensitizer. In this research, we demonstrate that a convention green fluorescent material, tris(8-hydroxyquinolinato)aluminum (Alq3) can be used as a sensitizer for a blue TTA emitter, 9,10-Bis(2-naphthyl)anthraces (ADN). In a conventional Alq3-based OLED, when the electron and hole coming from cathode and anode recombined at Alq3 as the recombination layer, 25% of singlet and 75% of triplet were generated. All triplet exciton experienced non-radiative recombination, which resulted in low efficiency due to the poor reverse intersystem crossing (RISC) rate. On the other hand, in TTAUC-OLED, triplet exciton of Alq3 (ET=2.0 eV) transferred the energy to the triplet of ADN (ET=1.67 eV) via Dexter energy transfer and two of them fused into one singlet (ES=2.83 eV) with blue emission. This recycled the useless triplet exciton and resulted in a higher external quantum efficiency (EQE) for TTAUC-OLED (2.1%) compared to the Alq3 (1.2%) and ADN (1.67%) control devices. Moreover, the recombination zone was shifted from ADN to Alq3, the operation lifetime of blue component can be increased by 3x times longer than the ADN control device. From transient electroluminescence (TrEL) measurement, Alq3-control device showed a fast decay within 1us which implied only singlet exciton involved. For the TTAUC-OLED, blue emission showed only delayed component which meant the emission came from only TTA process without direct recombination.

In this study, we demonstrated a blue phosphorescent organic light-emitting diode (BPOLED) based on a host with two carbazole and one trizole (2CbzTAZ) moiety, 9,9′-(2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)-1,3-phenylene)bis(9H-carbazole), that exhibits bipolar transport characteristics. Compared with the devices with a carbazole host (N,N’-dicarbazolyl-3,5-benzene, (mCP)), triazole host (3-(biphenyl-4-yl)-5-(4-tert-butylphenyl)-4-phenyl-4H-1,2,4-triazole, (TAZ)), or a physical mixture of mCP:TAZ, which exhibit hole, electron, and bipolar transport characteristics, respectively, the BPOLED with the bipolar 2CbzTAZ host exhibited the lowest driving voltage (6.55 V at 10 mA/cm2), the highest efficiencies (maximum current efficiency of 52.25 cd/A and external quantum efficiency of 23.89%), and the lowest efficiency roll-off, when doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic) as blue phosphor. From analyses of light leakage of the emission spectra of electroluminescence, transient electroluminescence, and partially doped OLEDs, it was found that the recombination zone was well confined inside the emitting layer and the recombination rate was most efficient in a 2CbzTAZ-based OLED. For the other cases using mCP, TAZ, and mCP:TAZ as hosts, electrons and holes transported with different routes that resulted in carrier accumulation on different organic molecules and lowered the recombination rate.

The novel ambipolar hosts of o-CbzBz and o-DiCbzBz contain carbazole and benzimidazole through an ortho-connection. The orthogonal conformations cause the triplet state to be confined at the carbazole units to secure efficient energy transfer. The phosphorescent organic light-emitting diodes (PhOLEDs) show a high current efficiency, power efficiency, and low efficiency roll-off. o-DiCbzBz can be used as a host for sky-blue, green, and orange-red PhOLEDs, giving 57.5, 78.4, and 60.3 cd/A, respectively.

Application of poly(Nʹ, Nʺ, N‴-tris[N, N-bis-(4ʹ-diphenylamino-biphenyl-4-yl)phenyl]-1, 3, 5-benzene tricarboxamide) (PG1), a triphenylamine dendritic polymer, in an complementary electrochromic device (ECD) has been studied. Electrochromic transitions of PG1 itself give very significant transmittance change (∆T) of 58.4% at 485 nm and 81.8% at 780 nm with rather good cycling stability. A complementary ECD based on the PG1 thin film and poly(3,4-ethylenedioxythiophene) (PEDOT) thin film was assembled to demonstrate panchromatic absorption characteristic through a simple fabrication process. This ECD exhibits black-to-transmissive electrochromism when switched from −0.4 to 1.5 V. Large variation in L* value in CIE L*a*b* coordinate (45.6) and ∆T (55.5% at 510 nm) is observed. In fact, the ∆T value achieved in this work is comparable to the highest value (58%) among all reported triphenylamine derivative/PEDOT ECDs after an extensive literature search. Furthermore, good cycling stability is achieved in the proposed ECD, which still retained panchromatic absorption characteristic and maintained 91.7% of the initial ∆T value at 510 nm after continuous 10,000 switchings.

An ambipolar material with a high triplet energy of 3.1 eV, 9-(2-(4,5-diphenyl-4H-1,2,4-triazol-3-yl)phenyl)-9H-carbazole (CbzTAZ), was synthesized by conjugating an electron-transporting 1,2,4-triazole and a hole-transporting carbazole and employed as the host doping with blue emitter iridium(III)bis[4,6-(difluorophenyl)-pyridinato-N,C2′]picolinate (FIrpic) to be the emitting layer (EML) of an efficient blue phosphorescent organic light-emitting diode (PhOLED). By adjusting the ratio between CbzTAZ and FIrpic, an efficient OLED performance with a current efficiency (ηC) of 50 cd/A and an external quantum efficiency (ηEQE) of 23.8% can be obtained. The position of the recombination zone located inside the EML close to the electron-transporting layer (ETL) can be detected by partially doping FIrpic in one of the three EML regions. By fine-tuning the thickness of the ETL to balance electrons and holes in the EML, a highly efficient blue PhOLED with a maximum ηC of 52.1 cd/A, a maximum power efficiency of 46...

Two novel bipolar carbzol-triazole derivatives was synthesized by conjugating hole transporting moiety carbazole (Cbz) with electron transporting moiety triazole (TAZ) to achieve the bipolar molecules, which were employed as the hosts of emitting layer doped with blue emitter FIrpic inside blue phosphorescence OLEDs with high current efficiency of 50 and 50.6 cd/A, and EQE of 20% and 21.6%.

A new multifunctional blue-emitting terfluorene derivative ( TFDPA ) featured with triphenylamine groups for hole-transportation and long alkyl chains for solution processability on the conjugation inert bridge centers was reported. TFDPA can give homogeneous thin film by solution process and exhibits high hole mobility ( μ h ≈ 10 −3 cm 2 V −1 s −1 ) and suitable HOMO for hole injection. Particularly, TFDPA performs efficient deep-blue emission with high quantum yield (∼100% in solution, 43% in thin film) and suitable triplet energy ( E T = 2.28 eV), making solution-processed OLED devices of using TFDPA as blue emitter and as host for iridium-containing phosphorescent dopants feasible. The solution-processed nondoped blue OLED device gives saturated deep-blue electroluminescence [CIE = (0.17, 0.07)] with EQE of 2.7%. TFDPA -hosted electrophosphorescent devices performed with EQE of 6.5% for yellow [(Bt) 2 Ir(acac)], 9.3% of orange [Ir(2–phq) 3 ], and 6.9% of red [(Mpq) 2 Ir(acac)], respectively. In addition, with careful control on the doping concentration of [(Bt) 2 Ir(acac)], a solution-processed fluorescence–phosphorescence hybrided two-color-based WOLED with EQE of 3.6% and CIE coordinate of (0.38, 0.33) was successfully achieved.

The two novel benzimidazole/carbazole hybrid ambipolar molecules, o-CbzDiBz and m-CbzDiBz, were synthesized as hosts for blue PHOLEDs. Bis[2-(4,6-diiluorophenyl)pyridinato-C2,N](picolinato)iridium(III) (FIrpic)-based devices can achieve 41.86 and 49.31 cd/A of current efficiency in o-CbzDiBz and m-CbzDiBz matrix, respectively.

We demonstrated a blue phosphorescent organic light-emitting diode with the maximum current efficiency and power efficiency of 57.4 cd/A and 51.6 lm/W, respectively, based on trizaole derivatives as the host of the emitting layer.

We reported a blue phosphorescent organic light-emitting diode (OLED) with the highest current efficiency of 55.2 cd/A, power efficiency of 50.5 lm/W and external quantum efficiency (EQE) of 24.8%, by using a tetraphenylsilane host in the emitting layer doped with blue emitter, bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolinato)iridium(in) (FIrpic).

A new organic host material, PCT comprising pyridine, carbazole and triazole moieties, was doped with a blue emitter bis[2-(4,6"difluorophenyl)pyridinato-C2,N](pico]inato)iridium(III) (FIrpic) to be an emitting layer (EML) of a phosphorescent organic light-emitting diodes device (PhOLED). With various FIrpic concentration (12%, 15% and 18% by volume ratio) in the EML, a series of high efficiency blue PhOLED was demonstrated showing the external quantum efficiency over 20%.

The soluble styrene polymers, bearing dicarbazole, phenylcarbazole or phenyltriphenylamine side groups were investigated as a host material for green emitter in phosphorescent PLED devices. Those polymers were synthesized by free radical polymerization via azobisisobutyronitrile (AIBN) as initiator under 75 °C. All of the host materials exhibit high thermal stability with high decomposition ( T d,5% weight loss > 398 °C) and glass transition temperatures ( T g > 172 °C). The HOMO ( ca. −5.39 ‒ −5.69 eV) and LUMO ( ca. −2.22 ‒ −2.41 eV) levels with the triplet energy of ca. 2.50–2.93 eV suggest that polymers are suitable for host materials for green emitter. The devices based on the emissive layers containing host materials doped with Ir(ppy) 3 (4 wt%) display stable green emission with high device performances. The brightness and current efficiency reach 15,800 cd/m 2 and 17.5 cd/A, respectively, at the optimum blending with 40 wt% 2-(4-biphenyl)-5-(4- tert -butylphenyl)-1,3,4-oxadiazol ( t- PBD). Furthermore, the device performance reached higher brightness (23,400 cd/m 2 ) and current efficiency (12.3 cd/A) when mixture with 2,4,6-triphenyl-1,3,5-triazine (TRZ) and t- PBD.

The study of the electrochemical fluorescence switching properties of the conjugated copolymers containing fluorene, triphenylamine, and 1,3-diphenylimidazolidin-2-one moieties is reported. The polymers show high fluorescence quantum yields, excellent thermal stability, and good solubility in polar organic solvents. While the polymer emits blue light under UV irradiation, the fluorescence intensity is quenched upon electrochemical oxidation. The fluorescent behavior can be reversibly switched between nonfluorescent (oxidized) state and strong fluorescence (neutral) state with a high contrast ratio (If/If0) of 16.3. The role of the electrochemical oxidation of the triphenylamine moieties is to generate the corresponding radical cations that lead to fluorescence quenching in the solid matrix. © 2012 Wiley Periodicals, Inc. J. Polym. Sci. Part A: Polym Chem, 2012

A series of novel oxygen-linked N-phenylcarbazole (NPC) dendritic wedges (3–5) and triphenylamine-centered dendrimers (CBD-G0 to -G2) have been synthesized and extensively studied. The aryl–oxygen–aryl (Ar–O–Ar) linkages were established on 3,6-positions of carbazole and 4-position of N-phenyl group. UV–vis spectra revealed that the Ar–O–Ar linkage would break down the π conjugation and make NPC units manifest their individual absorption moiety. Both steady-state luminescence and fluorescence decay dynamics at room temperature and 77 K in tetrahydrofuran suggested that the transfer of energy from the carbazole wedges to the triphenylamine (TPA) core operates in CBD-G1, so that the luminescence mainly arises from the core unit. The quenching of the emission from carbazole wedges by the TPA core becomes less effective as the generation develops into CBD-G2. The oxidation potential of the NPC derivatives clearly revealed the mesomeric electron-donating effect of the oxygen atom and inductive electron-withdra...

A photolithographic hole transport material of 4,4′,4″-tris(acetoxymethylene)triphenylamine (1), polyvinylcarbazole (PVK), and diphenyliodonium 9,10-dimethoxyanthracene-2-sulfonate (DIAS, a photoacid generator) has been successfully formulated. After exposure to UV irradiation (λ > 200 nm) through a patterned UV (λ >200 nm) photomask for 6 min, followed by a standard postbaking treatment at 130 °C for 5 min under vacuum and development in CH2Cl2, a negative tone image was established through the photoinduced chemical cross-linking reactions. This approach can be implemented to PLED applications. Under the optimized conditions, the polymeric light-emitting device (PLED) of ITO/photolithographic HTL/PVK–Ir(PPy)3–PBD/Mg–Ag, with a turn-on voltage of 13.0 V (100 cd/m2), a maximum brightness of 8220 cd/m2, and a current efficiency of 9.0 cd/A was achieved. Our study reviewed that three parallel mechanisms, including the photodimerization of the carbazole units, the Crivello onium salt sensitization mechanism, ...

A new class of triphenylamine substituted methanofullerene derivatives, bis(4'-(diphenylamino)biphenyl-4-yl)methanofullerene (1) and the bisadduct (2), were synthesized. The incident photon to current efficiency (IPCE) studies revealed that the diphenylamino components have contribution to the photocurrent that expands the light harvesting window around 400 nm. When being blended with poly (3-hexylthiophene) (P3HT) to fabricate the solar cell, the device of P3HT:1 (1:0.7) shows high open circuit voltage (Voc) of 0.69 V under the illumination of AM 1.5, 100 mW/cm2 with high power conversion efficiency (PCE) of 3.16%, which is about 0.1 V higher than that of the corresponding [6,6]-phenyl C61 butyric acid methyl ester (PCBM) devices. This indicates that the arylamine substituents on 1 have played some special roles on the high Voc performance. Similar effects are also observed for 2. The device of P3HT:2 (1:1) shows even higher Voc of 0.87 V with the PCE of 1.83%. These results indicate that 1 and 2 are alternative high performance acceptors.

Two novel conjugated polymers denoted TAZF2 and TAZBTF, having electron-deficient main chains and electron-rich triphenylamine pendant groups, were designed and synthesized. While TAZF2 was constructed with fluorene and electron-deficient 1,2,4-triazole as the major components of the main chain, fluorene, 1,2,4-triazole, and 2,1,3-benzothiadiazole were employed to form TAZBTF. The number-average molecular weights (Mw) of the polymers fell in the range of 1.28 × 104–2.56 × 104 with polydispersity indexes (PDI = Mw/Mn) of 1.49–1.95. The polymers had glass transition temperatures (Tg) in the range of 153–185 °C. While TAZF2 exhibited blue photoluminescence, TAZBTF exhibited yellow–green emission. Thermal stability of the conjugated polymers was enhanced due to the introduction of rigid bipolar components. The incorporation of 2,1,3-benzothiadiazole into TAZBTF reduced the coplanarity of the conjugated polymer, which prohibited the polymer from aggregation. Intramolecular and intermolecular energy transfer was clearly evidenced by the shift in light emission to the yellow–green region. TAZBTF exhibited maximum electroluminescence efficiency as high as 2.60 cd/A, demonstrating that a good balance of charge carriers is injected into our devices.

A novel carbazole-triazole derivative was used as a bipolar host of a phosphorescent blue organic light-emitting diode doped with bis[2-(4,6-difluorophenyl)pyridinato-C2,N](picolmato)iridmm(III) (FIrpic). Maximum current efficiency, power efficiency, and external quantum efficiency of this blue phosphorescent OLED reached 50.30 cd/A and 25.03%, respectively. Efficiency roll-off was alleviated due to the wide recombination zone, and current efficiency slightly reduced to 46.67 cd/A at 1000 cd/m2.

Through the Stille coupling polymerization, a series of soluble acceptor/donor quinoxaline/thiophene alternating conducting polymers with a hole-transporting moiety of carbazole as a side chain (PCPQT) has been designed, synthesized, and investigated. The UV-vis measurement of the charge-transferred type PCPQTs of different molecular weights with low polydispersity exhibits a red shifting of their absorption maximum from 530 to 630 nm with increasing chain length (M n : from 1100 to 19,200). The HOMO and LUMO energy levels of PCPQT can be determined from the cyclic voltammetry measurement to be -5.36 and -3.59 eV, respectively. Solar cells made from PCPQT/PCBM bulk heterojunction show a high open-circuit voltage, V oc of ∼0.75 V, which is significantly higher than that of a solar cell made from conventional poly(3-hexyl thiophene)/PCBM as the active polymer PCPQT has lower HOMO level. Further improvements are anticipated through a rational design of the new low band-gap and the structurally two-dimensional donor-acceptor conducting polymers.

New types of polyurethanes (PUs) were prepared from condensation polymerization of isophorone diisocyanate (IPDI) with various combination of 9-butyl-3,6-bis(4-hydroxyphenyl)carbazole (Cz) and 2,5-bis(4-hydroxyphenyl)-1,3,4-oxadiazole (OXD), and end-capped with 4- tert- butyl phenol. The Cz-OXD PUs can also be used as host for phosphorescent dye. Red EL emission was obtained when Ir(btp) 2 (acac) or Ir(2-phq) 2 (acac) was used as the phosphorescent dyes in Cz-OXD (3:1) PU. Maximum brightness of 394 cd/m 2 and EL efficiency of 1 cd/A were achieved for the Ir(2-phq) 2 (acac) base device. In addition, white light PLED was demonstrated when co-dopant of Ir(btp) 2 (acac) and Firpic were used.

We have synthesized a series of PPV copolymers and investigated the relationships between their chemical structures, thermal stabilities, and optoelectronic properties. Initially, we monitored the effects of the end group and the molecular weight on the behavior of polymer light emitting diodes (PLEDs) prepared from a series of oligo(phenylenevinylene) (OPV)-fluorene luminescent copolymers. We found that the nature of the end-capping group was an important factor affecting the luminescence properties of devices, which were improved especially when applying a triphenylamine end group. The molecular weight mainly affected the film quality of the manufactured device; that is, it improved to a certain degree when the molecular weight increased. Based on the luminescence conversion mechanism, we used a simple spin-coating process to fabricate a high-efficiency LED displaying white-light CIE 1931 (coordinates of 0.31, 0.34). The device exhibited a high current-efficiency of 3.5 cd/A and a brightness of 973 cd/m2. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 4504–4513, 2007

Dramatic photochromic-change of 2,5-bis(triphenylamine)-substituted N,N'-diphenylpyrrolo-[3,2-b]pyrrole (1) with halocarbons provides an effective route for halocarbon analysis with the naked eye. The visual detection range can reach as low as 10(-4) ∼ 10(-5) M (1-10 ppm) in CH3CN. This method can also be applied for detection of CHCl3 in water. Fabrication of a disposable paper test cartridge along with using a camera flash as the light source allows on-site halocarbon detection in seconds. Quantitative analysis for CHCl3 and CH2Cl2 have also been demonstrated.

The fluorescence and phosphorescence of 2,2'-bis(5-phenyl-1,3,4-oxadiazol-2-yl)biphenyl shows good spectral matching with the absorption spectra of the MLCT1 and MLCT3 transitions of Ir(ppy)3. The red-shift of the 0-0 band in the phosphorescence at 77 K is due to the intramolecular pi-pi interactions between the oxadiazole side chains. Maximum brightness of 43,000 cd/m2 with an efficiency of 26 cd/A at 200 cd/m2 was achieved when BOBP was used as the host material for Ir(ppy)3 in the PHOLED study. [structure: see text].

Substituent effects on the photophysical and electrochemical properties of 1,7-diaryl-substituted perylene diimides (1,7-Ar(2)PDIs) have been carefully explored. Progressive red-shifts of the absorption and emission maxima were observed when the electron-donating ability of these substituents was increased. Linear Hammett correlations of 1/lambda(max) versus sigma(+) were observed in both spectral analyses. The positive slopes of the Hammett plots suggested that the electronic transitions carry certain amounts of photoinduced intramolecular charge-transfer (PICT) character from the aryl substituents to the perylene diimide core which leads to the reduction of the electron density on the substituents. The substituent electronic effects originated mainly from the perturbation of the core PDI HOMO energy level by the substituents. This conclusion was supported by PM3 analyses and confirmed by cyclic voltammetry experiments. More interestingly, the Ph(2)NC(6)H(4)-substituted PDI, 4i, showed an unusual dual-band absorption that spans from 450 to 750 nm. We tentatively assigned these two bands as the charge-transfer band and the PDI core absorption, respectively.

A high efficiency blue phosphorescence organic light emitting device (OLED) was demonstrated by using a novel electron transporting and wide band gap material, CbzTAZ, as host doping with blue emitter, iridium(III)bis[4,6-(di-fluorophenyl)-pyridinato-N, C2′]picolinate (FIrpic). By adjusting the doping ratio of FIrpic and the thickness of emitting layer, we obtained an efficient blue phosphorescence OLED with high current efficiency over 45 cd/A and high external quantum efficiency over 23%.

The development of benzimidazole substituted biphenyls as electron-transporting hosts for bis[2-(4,6-difluorophenyl)pyridinato-C(2),N](picolinato)iridium(III) is reported. Under the optimized conditions, the organic light-emitting diode (OLED) achieves the maximum current efficiency of 57.2 cd/A, power efficiency of 50.4 lm/W, and external quantum efficiency 25.7%.

The fluorescent behavior of the electrofluorochromic devices (Type I) of greenish-yellow emitting P1 and blue emitting P2 can be reversibly switched between the nonfluorescent (oxidized) state and the fluorescent (neutral) state with a superb on/off ratio of 23.8 and 21.9, respectively. Moreover, a tunable electrofluorochromic device (Type II) based on two P1 and P2 polymeric layers that are coated individually on two independent ITO electrodes shows switchable blue-white-(greenish-yellow) multifluorescence states.

A chemically amplified resist material consisting of poly[2-cyano-2-(p-vinylphenyl) butanoic acid] and bis[[(2-nitrobenzyl)oxy]carbonyl]hexane-1,6-diamine has been designed and tested in negative and positive tone imaging. The resist operates on the principle of base-catalyzed decarboxylation. Amine generated by exposure to UV radiation catalyzes the thermal loss of carbon dioxide from the polymer side chain thereby changing the solubility of the resist film in aqueous base developer. Image reversal is accomplished by in situ silylation of the exposed and thermolyzed film followed by dry development using an oxygen plasma. The resist shows high sensitivity to deep UV irradiation, ca. 10 mJ/cm2, while image contrast is excellent.

Multi-(5-phenyl-1,3,4-oxadiazo-2-yl)benzenes show emission in organic solvents from ultraviolet to blue (339-447 nm). The reduction potentials E(1/2)(red) cover a large range of -2.11 V for 2,5-diphenyl-1,3,4-oxadiazole to -0.76 V for 1,2,3,4,5,6-hexa(5-phenyl-1,3,4-oxadiazo-2-yl)benzene. An unexpectedly wide spectral range of the oxadiazole (OXD) exciplex emissions in PVK is observed, ranging from 406 to 603 nm. The OXDs also exhibit similar electroluminescence (EL) when blended into polyvinylcarbazole (PVK). A linear correlation between the lambda(max) of the electroluminescence and photoluminescence is observed, implying that the emission mechanisms in both processes are similar. In addition, the linear correlation between the E(1/2)(red) versus lambda(max) of EL (eV) reflected that the term of the charge-transfer configuration of the contact electron-hole pair plays a major role in the exciplex emission. The exciplex EL of 1,2,5-tri(5-phenyl-1,3,4-oxadiazo-2-yl)benzene (5) could be as high as 1.0 cd/A. Since the exciplex emission usually has a large Stokes shift, this provides a window for us to generate duo emissions for near white light EL with high efficiency. Among the devices we tried, the device of PVK/2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole/5/2,5,8,11-tetra-tert-butylperylene (100:40:40:4) gave EL with good current efficiency of 1.63 cd/A.

In this experiment, a series of thermal reactions of 4,4'-disubstituted 2,2'-bis(phenylethynyl)biphenyls with 2,3,4,5-tetraphenylcyclopenta-2,4-dienone were carried out under neat conditions and in diphenyl ether at temperatures between 260 and 270 degrees C to give rise to 9,10,11,12,13,14-hexaphenylcycloocta[l]phenanthrenes as the adducts in 12-23% yields. We traced these results to the intramolecular [2 + 2] thermal cyclization of 2,2'-bis(phenylethynyl)biphenyls to form 1,2-diphenylcyclobuta[l]phenanthrenes, which were further trapped as bridged-ketone Diels-Alder adducts, followed by thermal decarbonylative ring opening, which gave rise to the products.

Dye-doped organic light-emitting diode of ITO/alpha-NPB (70 nm)/Bebq(2)-1 (7 nm)/BCP (5 nm)/Bebq(2) (33 nm)/LiF (1 nm)/Al (150 nm) shows red electroluminescence with the efficiency of 2.9 cd/A at 100 cd/m(2) and maximum brightness of 62000 cd/m(2). The physical organic aspects of the current-induced fluorescent quenching effect are discussed. [structure: see text]

Under UV irradiation, 1,4-bis(5-(4-octan-2-ylphenyl)-1,3,4-oxadiazol-2-yl)naphthalene (NOXD) and poly(fluorenetolyldiphenylamine) (PFT) are blue light emissive in solid film. When NOXD and PFT were blended to form a neat thin-film, yellowish exciplex emission was observed. The emissive properties vary when the materials were blended into different kinds of polymeric hosts; while polystyrene–NOXD–PFT (5 : 1 : 1) and PMMA–NOXD–PFT (5 : 1 : 1) showed blue light emission, poly(acrylonitrile-co-methyl acrylate) (P(AN-co-MA))–NOXD–PFT (5 : 1 : 1) showed blue and yellow dual emissions. When the film was heated at 140 °C for 2 min, the yellow light exciplex emission was enhanced. However, upon cooling to ambient temperature, the exciplex emission intensity gradually dropped back. Similar thermofluoric behaviors were observed when the thermally crosslinked polyepoxy-polymercaptan–NOXD–PFT film (20 : 1 : 1) was heated at 160–170 °C; the blue light emissive film showed yellow light emission, and turned white when cooling down to ambient temperature. This thermofluoric phenomenon is recyclable. We attributed the observation of the yellow emission to the segregation of NOXD from the polymeric host at high temperature that allows NOXD to aggregate with PFT, leading to exciplex emission.

In this latter, the authors demonstrated a phosphorescent organic light-emitting device (OLED) with a lower driving voltage and a longer operation lifetime based on 2,2′-bis[5-phenyl-2-(1,3,4)oxadazolyl]biphenyl, an oxadiazole (OXD) derivative, as the host of the emitting layer doped with a common green-emitting phosphorescent dopant, fac-tris(2-phenylpyridine) iridium [Ir(ppy)3]. Rather than an electron transporting materials, the OXD exhibits an ambipolar transport characteristic with suitable Ir(ppy)3 concentrations due to its low highest occupied molecular orbital value (5.9eV) and the hole-transporting characteristics of Ir(ppy)3. It results in a 2.4V voltage reduction and a 2.6 times lifetime elongation of the OXD-based device, as compared to the conventional phosphorescent OLED.

A novel strategy derived from sulfur-based cyclocoupling in conjunction with a modified Ramberg–Backlund reaction together with the utilization of (–)-methol as the chiral auxiliary is presented for the synthesis of (+)- and (–)-[12][12]paracyclophanes.