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Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( Pedot PSS) films as transparent electrodes for organic light-emitting diodes (OLEDs) are doped with a new solvent 1,3-dimethyl-2-imidazolidinone (DMI) and are optimized using solvent post-treatment. The DMI doped Pedot PSS films show significantly enhanced conductivities up to 812.1 S cm(-1) . The sheet resistance of the Pedot PSS films doped with DMI is further reduced by various solvent post-treatment. The effect of solvent post-treatment on DMI doped Pedot PSS films is investigated and is shown to reduce insulating PSS in the conductive films. The solvent posttreated Pedot PSS films are successfully employed as transparent electrodes in white OLEDs. It is shown that the efficiency of OLEDs with the optimized DMI doped Pedot PSS films is higher than that of reference OLEDs doped with a conventional solvent (ethylene glycol). The results present that the optimized Pedot PSS films with the new solvent of DMI can be a promising transparent electrode for low-cost, efficient ITO-free white OLEDs.

To improve a viewing angle characteristic as well as a light extraction effect, we fabricated nanoporous polymer film (NPF) as a scattering medium as well as a light extraction component. We designed two types of organic light emitting diodes (OLEDs) with strong microcavity effect containing two different hole transport layer (HTL) thickness (e.g. 30 nm and 60 nm) to investigate each optical behavior of NPF. Very interestingly, we could observe a significant enhancement of external quantum efficiency (EQE) for each device [30 nm thick HTL : 18.0 %, 60nm thick HTL : 31.6 %] when we attached 125 um thick PET film coated with NPF. Furthermore, NPF successfully suppress the viewing angle dependence to realize ideal angular emission even though it's somehow different from that of Lambertian distribution.

We have fabricated transparent inverted organic light-emitting diodes (OLEDs) using a metal mesh embedded conductive film (MEF) with a non-metal transparent conductor and a novel vacuum lamination method. The device with the proposed electrode exhibits higher transmittance, lower reflectance, and especially much more stable optical properties than those of the conventional OLEDs with thin metal top electrodes over an entire visible region. Moreover, lower driving voltage is also achieved due to the embedded metal mesh. We demonstrate its potential as a reliable transparent top electrode in various optoelectronic devices.

We report on highly efficient blue, orange, and white phosphorescent organic light emitting diodes (PHOLEDs) comprising of only two organic layers. Hole transporting 4,4’,4’’-tris(N-carbazolyl)triphenylamine (TcTa) and electron transporting 2-(diphenylphosphoryl) spirofluorene (SPPO1) were used as an emitting host for orange light-emitting bis(3-benzothiazol-2-yl-9-ethyl-9Hcarbazolato) (acetoacetonate) iridium ((btc)2(acac)Ir) and blue light-emitting iridium(III)bis(4,6-difluorophenylpyridinato-N,C2’) picolinate (FIrpic) dopant, respectively. Combining these two orange and blue light-emitting layers, we successfully demonstrated a highly efficient white PHOLEDs with maintaining Commission Internationale de L’Eclairage (CIE) coordinates of (x = 0.373, y = 0.443). Accordingly, we achieved a maximum external quantum, current, and power efficiencies of 12.9 %, 30.3 cd/A, and 30.0 lm/W without out-coupling enhancement.

We report on a novel fabrication method for organic lightemitting diodes (OLEDs) by using a multilayered graphene (MLG) film and a lamination technique. The OLED structure with the MLG top electrode has higher transmittance and lower reflectance than the OLED structure with the conventional thin metal electrode. Moreover, higher luminous current efficiency of the device with the MLG top electrode has been achieved compared with that of the conventional bottom-emission OLEDs with aluminum metal electrode.

We developed a highly refractive index planarization layer showing a very smooth surface for organic light-emitting diode (OLED) light extraction, and we successfully prepared a highly efficient white OLED device with an embossed nano-structure and highly refractive index planarization layers. White OLEDs act as an internal out-coupling layer. We used a spin-coating method and two types of TiO2 solutions for a planarization of the embossed nano-structure on a glass substrate. The first TiO2 solution was TiO2 sol, which consists of TiO2 colloidal particles in an acidic aqueous solution and several organic additives. The second solution was an organic and inorganic hybrid solution of TiO2. The surface roughness (Ra) and refractive index of the TiO2 planarization films on a flat glass were 0.4 nm and 2.0 at 550 nm, respectively. The J–V characteristics of the OLED including the embossed nano-structure and the TiO2 planarization film were almost the same as those of an OLED with a flat glass, and the luminous efficacy of the aforementioned OLED was enhanced by 34% compared to that of an OLED with a flat glass.

We suggest a new approach to improve both out-coupling efficiency and spectrum independency on viewing angle in transparent OLEDs by introducing a random nano-structured scattering layer where the waveguide mode can be minimized between the glass substrate and the ITO layer. As a result, total efficiency was remarkably enhanced in transparent OLEDs and we have achieved 52.6 lm/W with CRI 80 with over 50% of transmittance using the random nano-structured scattering layer.

We report that a potassium borohydride (KBH4)-doped 1,3,5-tri(m-pyrid-3-yl-phenyl)benzene (TmPyPB) layer can be utilized as an efficient electron-injection layer (EIL) for the inverted bottom-emission organic light-emitting diodes (IBE-OLEDs). The KBH4-doped EIL in the IBE-OLEDs having tris(2-phenylpyridine)iridium(III) as a green phosphorescent dopant show a lower turn-on voltage (∼7 V) and about two times higher efficiency (∼13.9% and 44.5 cd A−1 at 0.63 mA cm−2) compared with the device without the KBH4-doped EIL. Furthermore, the KBH4-doped EIL rarely affects the electroluminescence spectrum of the device. The KBH4-doped TmPyPB films with different doping ratios are also analyzed by using electron-only devices (EODs) and X-ray photoemission spectroscopy. As the doping ratio of the KBH4 increases, the current of the EOD and the amounts of potassium increase. This result indicates that the potassium improves the electron-injection ability of an organic electron-transport layer. Therefore, the KBH4-doped EIL can be utilized as an effective EIL in the inverted structure OLEDs.

In this work, we develop a simulation method to predict a two-dimensional luminance distribution method using a circuitry simulation. Based on the simulation results, we successfully fabricate large area (90 mm × 90 mm) transparent organic light-emitting diode panels with high luminance uniformity.

We used the magnetic resonant wireless power transmission technology to lit thin OLED lighting panels. For the magnetic resonant wireless power transmission, we used small and thin four layer printed circuit board for the receiver. The resonant frequency is lowered up to 457 kHz for the electromagnetic regulation.

We investigate the light-emitting performances of blue phosphorescent organic light-emitting diodes (PHOLEDs) with three different electron injection and transport materials, that is, bathocuproine(2,9-dimethyl-4,7diphenyl-1,10-phenanthroline) (Bphen), 1,3,5-tri(m-pyrid3-yl-phenyl)benzene (Tm3PyPB), and 2,6-bis(3-(carbazol9-yl)phenyl)pyridine (26DCzPPy), which are partially doped with cesium metal. We find that the device characteristics are very dependent on the nature of the introduced electron injection layer (EIL) and electron transporting layer (ETL). When the appropriate EIL and ETL are combined, the peak external quantum efficiency and peak power efficiency improve up to 20.7% and 45.6 lm/W, respectively. Moreover, this blue PHOLED even maintains high external quantum efficiency of 19.6% and 16.9% at a luminance of 1,000 cd/m 2 and 10,000 cd/m 2 , respectively.

This paper reports on a study of the electrical properties of integrated organic light emitting diode (OLED) with an organic photo sensor (OPS) based on poly-3-hexylthiophene (P3HT) and [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) for emotional lighting applications. The emission characteristics exhibit the changes in the current and luminance of an OLED as a function of time when the OPS is exposed to different illumination levels from full dark to 500 m W/cm2 using a xenon lamp.

We investigated the light-emitting performances of blue phosphorescent organic light-emitting diodes, known as PHOLEDs, by incorporating an N,N'-dicarbazolyl-3,5-benzen interlayer between the hole transporting layer and emitting layer (EML). We found that the effects of the introduced interlayer for triplet exciton confinement and hole/electron balance in the EML were exceptionally dependent on the host materials: 9-(4-tert-butylphenyl)-3,6-bis(triphenylsilyl)-9H-carbazole, 9-(4-tert-butylphenyl)-3,6-ditrityl-9H-carbazole, and 4,4'-bis-triphenylsilanyl-biphenyl. When an appropriate interlayer and host material were combined, the peak external quantum efficiency was greatly enhanced by over 21 times from 0.79% to 17.1%. Studies on the recombination zone using a series of host materials were also conducted.

Graphene produced by chemical vapor deposition (CVD) has attracted great interest as a transparent conducting material, due to its extraordinary characteristics such as flexibility, optical transparency, and high conductivity, especially in next-generation displays. Graphene-based novel electrodes have the potential to satisfy the important factors for high-performance flexible organic light-emitting diodes (OLEDs) in terms of sheet resistance, transmittance, work function, and surface roughness. In this study, flexible and transparent graphene electrode architecture is proposed by adopting a selective defect healing technique for CVD-grown graphene, which results in several benefits that produce high-performance devices with excellent stabilities. The proposed architecture, which has a multi-layer graphene structure treated by a layer-by-layer healing process, exhibits significant improvement in sheet resistance with high optical transparency. For improving the charge transport property and mechanical robustness, various defect sites of the CVD-grown graphene are successfully decorated with gold nanoparticles through a simple electroplating (EP) method. Further, a graphene-based OLED device that integrates the proposed electrode architecture on flexible substrates is demonstrated. Therefore, this architecture provides a new strategy to fabricate graphene electrode in OLEDs, extending graphene's immense potential as an advanced conductor toward high-performance, flexible, and transparent displays.

Highly efficient white phosphorescent organic light- emitting diodes with a mixed-host structure are developed and the device characteristics are studied. The introduction of a hole-transport-type host (N, N'- dicarbazolyl-3-3-benzen (mCP)) into an electron- transport-type host (m-bis-(triphenylsilyl)benzene (UGH3)) as a mixed-host emissive layer effectively achieves higher current density and lower driving voltage. The peak external quantum and power efficiency with the mixed-host structure improve up to 18.9% and 40.9 lm/W, respectively. Moreover, this mixed-host structure device shows over 30% enhanced performance compared with a single-host structure device at a luminance of 10,000 cd/m 2 without any change in the electroluminescence spectra.

We synthesized two fluorene-based copolymers poly[(2,5-bis(4-hexylthiophen-2-yl)thiazolo[5,4-day]thiazole-5,5'-diyl)-alt-(9,9'-dioctylfluorene-2,7-diyl)1 (PF-TTZT), and poly[(5,5'-bis(4-hexylthiophen-2-yl)-2,2'-bithiazole-5,5'-diyl)-alt-(9,9'-dioctylfluorene-2,7-diyl)] (PF-TBTT), which contain the electron-withdrawing moieties, thiazolothiazole, and bithiazole, respectively. Through electrochemical studies, we found that these two polymers exhibit stable reversible oxidation and reduction behaviors. Moreover, the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy levels of PF-TBTT are lower than those of PF-TTZT, and the bandgap of PF-TBTT is smaller than that of PF-TTZT. Thus the bithiazole moiety in PF-TBTT is more electron-withdrawing than the thiazolothiazole moiety in PF-TTZT. Light-emitting devices with indium tin oxide (ITO)/poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate)(PEDOT)/polymer/bis(2-methyl-8-quinolinato)-4-phenylphenolate aluminum (BAlq)/LiF/Al configurations were fabricated. The performance of the PF-TBTT device was found to be almost three times better than that of the PF-TTZT device, which is because electron injection from the cathode to PF-TBTT is much easier than for PF-TTZT. We also investigated the planarity and frontier orbitals of the electron donor-acceptor (D-A) moieties with computational calculations using ab initio Hartree-Fock with the split-valence 6-31G* basis set. These calculations show that TBTT has a more nonplanar structure than TTZT and that the bithiazole moiety is more electron-withdrawing than thiazolothiazole. These calculations are in good agreement with the experimental results.

The stability of ZnO TFT under bias stress was investigated. Transparent ZnO thin films deposited by means of atomic layer deposition(ALD) and plasma enhanced atomic layer deposition(PEALD) at 100 °C were used as the active channel. The TFT with PEALD grown ZnO layer has better stability under bias stress than the TFT with ALD grown ZnO layer.

A novel series of poly(10-hexyl-phenothiazine-S,S'-dioxide-3,7-diyl) and poly(9,9'-dioctyl-fluorene-2,7-diyl-alt-10-hexyl-3,7-phenothiazine-S,S'-dioxide) (PFPTZ-SS) compounds were synthesized through Ni(0)-mediated Yamamoto polymerization and Pd(II)-catalyzed Suzuki polymerization. The synthesized polymers were characterized by 1 H NMR spectroscopy and elemental analysis and showed higher glass transition temperatures than that of pristine polyfluorene. In terms of photoluminescence (PL), the PFPTZ-SS compounds were highly fluorescent with bright blue emissions in the solid state. Light-emitting devices were fabricated with these polymers in an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration. The electroluminescence (EL) of the copolymers differed from the PL characteristics: the EL device exhibited a redshifted greenish-blue emission in contrast to the blue emission observed in the PL. Additionally, this unique phenothiazine-S,S-dioxide property, triggered by the introduction of an electron-deficient SO 2 unit into the electron-rich phenothiazine, gave rise to improvements in the brightness, maximum luminescence intensity, and quantum efficiency of the EL devices fabricated with PFPTZ-SS.

Novel conjugated polyfluorene copolymers, poly[9,9-dihexylfluorene-2,7-diyl-co-(2,5-bis(4′-diphenylaminostyryl)-phenylene-1,4-diyl)]s (PGs), have been synthesized by nickel(0)-mediated polymerization from 2,7-dibromo-9,9-dihexylfluorene and 1,4′-dibromo-2,5-bis(4-diphenylaminostyryl)benzene with various molar ratios of the monomers. Because of the incorporation of triphenylamine (TPA) moieties, PGs exhibit much higher HOMO levels than the corresponding polyfluorene homopolymers and are able to facilitate hole injection into the polymer layer from the anode electrode in light-emitting diodes. Conventional polymeric light-emitting devices with the configuration ITO/PEDOT:PSS/polymer/Ca/Al have been fabricated. A light-emitting device produced with one of the PG copolymers (PG10) as the emitting layer exhibited a voltage-independent and stable bluish-green emission with color coordinates of (0.22, 0.42) at 5 V. The maximum brightness and current efficiency of the PG10 device were 3370 cd/m2 (at 9.6 V) and 0.6 cd/A, respectively. To realize a white polymeric light-emitting diode, PG10 as the host material was blended with 1.0 wt % of a red-light-emitting polymer, poly[9,9-dioctylfluorene-2,7-diyl-alt-2,5-bis(2-thienyl-2-cyanovinyl)-1-(2′-ethylhexyloxy)-4-methoxybenzene-5′,5′-diyl] (PFR4-S), and poly[2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV). The device based on PG10:PFR4-S showed an almost perfect pure white electroluminescence emission, with Commission Internationale de l'Eclairage (CIE) coordinates of (0.33, 0.36) at 8 V; for the PG10:MEH-PPV device, the CIE coordinates at this voltage were (0.30, 0.40) with a maximum brightness of 1930 cd/m2. Moreover, the white-light emission from the PG10:PFR4-S device was stable even at different driving voltages and had CIE coordinates of (0.34, 0.36) at 6 V and (0.31, 0.35) at 10 V. © 2007 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 45: 1199–1209, 2007

A series of fluorene-based copolymers composed of blue- and orange-light-emitting comonomers were synthesized through palladium-catalyzed Suzuki coupling reactions. 9,9-Dihexylfluorene and 2-(2,6-bis-{2-[1-(9,9-dihexyl-9H-fluoren-2-yl)-1,2,3,4-tetrahydroquinolin-6-yl]-vinyl)-pyran-4-ylidene)-malononitrile (DCMF) were used as the blue- and orange-light-emitting chromophores, respectively. The resulting single polymers exhibited simultaneous blue (423/450 nm) and orange (580-600 nm) emissions from these two chromophores. By adjusting the fluorene and DCMF contents, white light emission could be obtained from a single polymer; a device with an ITO/ PEDOT:PSS/polymer/Ca/Al configuration was found to exhibit pure white electroluminescence with Commission Internationale de L'Eclairage (CIE) coordinates of (0.33, 0.31), a maximum brightness of 1180 cd/m 2 , and a current efficiency of 0.60 cd/A. Furthermore, the white light emission of this device was found to be very stable with respect to variation of the driving voltage. The CIE coordinates of the device were (0.32, 0.29), (0.32, 0.29), and (0.33, 0.31) for driving voltages of 7, 8, and 10 V, respectively.

Two novel organic–inorganic hybrid polyfluorene derivatives, poly{(9,9′-dioctyl-2,7-fluorene)-co-(9,9′-di-POSS-2,7-fluorene)-co-[2,5-bis(octyloxy)-1,4-phenylene]} (PFDOPPOSS) and poly{(9,9′-dioctyl-2,7-fluorene)-co-(9,9′-di-POSS-2,7-fluorene)-co-bithiophene} (PFT2POSS), were synthesized by the Pd-catalyzed Suzuki reaction of polyhedral oligomeric silsesquioxane (POSS) appended fluorene, dioctyl phenylene, and bithiophene moieties. The synthesized polymers were characterized with 1H NMR spectroscopy and elemental analysis. Photoluminescence (PL) studies showed that the incorporation of the POSS pendant into the polyfluorene derivatives significantly enhanced the fluorescence quantum yields of the polymer films, likely via a reduction in the degree of interchain interaction as well as keto formation. Additionally, the blue-light-emitting polyfluorene derivative PFDOPPOSS showed high thermal color stability in PL. Moreover, single-layer light-emitting diode devices of an indium tin oxide/poly(3,4-ethylene dioxythiophene):poly(styrene sulfonate)/polymer/Ca/Al configuration fabricated with PFDOPPOSS and PFT2POSS showed much improved brightness, maximum luminescence intensity, and quantum efficiency in comparison with devices fabricated with the corresponding pristine polymers PFDOP and PFT2. In particular, the maximum external quantum efficiency of PFT2POSS was 0.13%, which was twice that of PFT2 (0.06%), and the maximum current efficiency of PFT2POSS was 0.38 cd/A, which again was twice that of PFT2 (0.19 cd/A). © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 44: 2943–2954, 2006

A series of fluorene-thiophene-based semiconducting materials, poly(9,9'-dioctylfluorene-alt-α,α'-bisthieno[3,2-b]thiophene) (F8TT2), poly(9,9'-di(3,6-dioxaheptyl) fluorene-alt-thieno[3,2-b]thiophene) (BDOHF8TT), poly(9,9'-di(3,6-dioxaheptyl)fluorene-alt-bithiophene) (BDOHF8T2), and poly(9,9'-dioctylfluorene-co-bithiophene-co-[4-(2-ethylhexyloxyl)phenyl]diphenylamine) (F8T2TPA), was synthesized through a palladium-catalyzed Suzuki coupling reaction. F8TT2, BDOHF8TT, BDOHF8T2, and F8T2TPA films exhibited photoluminescence maxima at 523, 550, 522, and 559 nm, respectively. Solution-processed field-effect transistors (FETs) fabricated with all the copolymers except F8T2TPA showed p-type organic FET characteristics. Studies of the differential scanning calorimetry scans and FETs of the polymers revealed that more crystalline polymers gave better FET device performance. The greater planarity and rigidity of thieno[3,2-b]thiophene in comparison with bithiophene resulted in higher crystallinity of the polymer backbone, which led to improved FET performance. On the other hand, the random incorporation of the triphenylamine moiety into F8T2TPA caused the polymer chains to lose crystallinity, resulting in an absence of FET characteristics. With this study, we could assess the liquid-crystallinity dependence of the field-effect carrier mobility on organic FETs based on liquid-crystalline copolymers.

We have carried out the fabrications of a barrier layer on a polyethersulfon (PES) film and organic light emitting diode (OLED) based on a plastic substrate by means of atomic layer deposition (ALD). Simultaneous deposition of 30 nm AlOx film on both sides of the PES film gave a water vapor transition rate (WVTR) of 0.062 g/m 2 /day (@38°C, 100% R.H.). Further, the double layer of 200 nm SiNx film deposited by plasma enhanced chemical vapor deposition (PECVD) and 20 nm AlOx film by ALD resulted in a WVTR value lower than the detection limit of MOCON. We have investigated the OLED encapsulation performance of the double layer using the OLED structure of ITO / MTDATA (20 nm) / NPD (40 nm) / AlQ (60 nm) / LiF (1 nm) / Al (75 nm) on a plastic substrate. The preliminary life time to reach 91% of the initial luminance (1300 cd/m 2 ) was 260 hours for the OLED encapsulated with 100 nm of PECVD-deposited SiNx and 30 nm of ALD-deposited AlOx.

High quality indium tin oxide (ITO) thin films were grown by pulse laser deposition (PLD) on flexible polyethersulphone (PES) substrates. The electrical, optical, and surface morphological properties of these films were examined as a function of substrate temperature and oxygen pressure. ITO thin films, deposited by PLD on a PES substrate at room temperature and an oxygen pressure of 15 mTorr, have a low electrical resistivity of 2.9×10 - 4 Ω cm and a high optical transmittance of 84 % in the visible range. They were used as the anode in organic light-emitting diodes (OLEDs). The maximum electro luminescence (EL) and current density at 100 cd/m 2 were 2500 cd/m 2 and 2 mA/cm 2 , respectively, and the external quantum efficiency of the OLEDs was found to be 2.0 %.

We report here the synthesis via Suzuki polymerization of two novel alternating polymers containing 9,9-dioctylfluorene and electron-withdrawing 4,4′-dihexyl-2,2′-bithiazole moieties, poly[(4,4′-dihexyl-2,2′-bithiazole-5,5′-diyl)-alt-(9,9-dioctylfluorene-2,7-diyl)] (PHBTzF) and poly[(5,5′-bis(2″-thienyl)-4,4′-dihexyl-2,2′-bithiazole-5″,5″-diyl)-alt-(9,9-dioctylfluorene-2,7-diyl)] (PTHBTzTF), and their application to electronic devices. The ultraviolet–visible absorption maxima of films of PHBTzF and PTHBTzTF were 413 and 471 nm, respectively, and the photoluminescence maxima were 513 and 590 nm, respectively. Cyclic voltammetry experiment showed an improvement in the n-doping stability of the polymers and a reduction of their lowest unoccupied molecular orbital energy levels as a result of bithiazole in the polymers' main chain. The highest occupied molecular orbital energy levels of the polymers were −5.85 eV for PHBTzF and −5.53 eV for PTHBTzTF. Conventional polymeric light-emitting-diode devices were fabricated in the ITO/PEDOT:PSS/polymer/Ca/Al configuration [where ITO is indium tin oxide and PEDOT:PSS is poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonic acid)] with the two polymers as emitting layers. The PHBTzF device exhibited a maximum luminance of 210 cd/m2 and a turn-on voltage of 9.4 V, whereas the PTHBTzTF device exhibited a maximum luminance of 1840 cd/m2 and a turn-on voltage of 5.4 V. In addition, a preliminary organic solar-cell device with the ITO/PEDOT:PSS/(PTHBTzTF + C60)/Ca/Al configuration (where C60 is fullerene) was also fabricated. Under 100 mW/cm2 of air mass 1.5 white-light illumination, the device produced an open-circuit voltage of 0.76 V and a short-circuit current of 1.70 mA/cm2. The fill factor of the device was 0.40, and the power conversion efficiency was 0.52%. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 1845–1857, 2005

With the progress of organic electronics, materials possessing various functionalities are attracting much attention. Here we have synthesized a novel photo-alignment polymer composed of a conjugated carbazole main-chain and a coumarin side-chain through nickel(0)-mediated polymerization. Carbazole is a well-known hole transporting material and coumarin is also famous for its good photo-alignment properties. The photochemical reactivity of thecoumarin side-chain was monitored by UV-vis spectroscopy and the liquid crystal (LC) photo-alignment direction of the polymer film was proved to be perpendicular to the polarization direction of the irradiated UV light. the highest occupied molecular orbital (HOMO) level of the polymer, measured from both cyclic voltammetry and photoelectron spectroscopy, was -5.32 eV. Organic light-emitting diodes (OLEDs) of the configuration [ITO/polymer/NPB/Alq 3 /LiF/Al] showed a higher efficiency (2.17%) and brightness (14000 cd.m -2 ) than a control device due to enhanced charge balance.

This paper investigates the absorption and emission changes in poly(di-n-hexylfluorene)s. We prepared the poly(di-n-hexylfluorene)s end capped with 2-bromofluorene, 2-bromo-9,9-di-n-hexylfluorene, and 9-bromoanthracene through Ni (0) mediated polymerization. In addition, we also synthesized a structurally distorted copolymer of 2,7dibromo-9,9-di-n-hexylfluorene and 9,9-bis(4-bromophenyl) fluorene end capped with 2-bromofluorene through the same polymerization method. The absorption and emission changes of these polymers between before and after thermal annealing in a nitrogen atmosphere clarify the role of aggregate/excimer formation in poly(fluorene)s. The large absorption changes must be attributed to aggregate formation (ground state interaction), which causes only a slight red shift of the vibronically structured emission bands. We assign the additional long wavelength emission as an excimer band (excited state interaction), which is preferably formed at chain ends.

A single-chamber system capable of depositing both organic and inorganic layers by initiated chemical vapor deposition (iCVD) and atomic layer deposition (ALD) is demonstrated to facilitate the fabrication of organic/inorganic hybrid thin film encapsulation (TFE). The chamber geometry and the process conditions of iCVD and ALD are similar to each other, which enabled the design of the single-chamber system. Both organic and inorganic films deposited via the single-chamber system produces films with their properties equivalent to those deposited in separate iCVD and ALD reactors. Alternating the deposition mode between iCVD and ALD produces organic/inorganic multilayers with outstanding barrier properties as well as optical transparency mechanical flexibility.

We report on the bias stability characteristics of transparent ZnO thin film transistors (TFTs) under visible light illumination. The transfer curve shows virtually no change under positive gate bias stress with light illumination, while it shows dramatic negative shifts under negative gate bias stress. The major mechanism of the bias stability under visible illumination of our ZnO TFTs is thought to be the charge trapping of photo-generated holes at the gate insulator and/or insulator/channel interface.

Poly[2-(5-cyclohexylmethoxypentyloxy)-5-methoxy-1,4-phenylenevinylene] (PMCYHPV) was synthesized through dehydrohalogenation polymerization. This polymer shows good solubility in common organic solvents. The absorption and photoluminescence (PL) emission maxima of PMCYHPV are 497 nm and 590 nm, respectively. The electroluminescence (EL) properties of poly[2-methoxy-5-(2-ethylhexyloxy)-1,4-phenylenevinylene] (MEH-PPV) and PMCYHPV were studied by means of the EL spectra, current-voltage characteristics, and EL power-current characteristics. The measured relative EL quantum efficiency of PMCYHPV is about 6 times higher than that of MEH-PPV. The EL enhancement of PMCYHPV originates from the reduction of non-radiative decay of excitons caused by better separation of the polymer chains due to the rigid cyclohexyl side group. Furthermore, we found that the PL quantum efficiency of PMCYHPV is 15% higher than that of MEH-PPV.