A correlation between electrochemical properties and geometrical structure of some triarylamines used as hole transporting materials in organic electroluminescent devicesElectronic supplementary information (ESI) available: Optimised Cartesian coordinates calculated using AM1 of: 1. TPA 2. TTA 3.... (original) (raw)
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High-TgN-Triarylamine Derivatives as a Hole Injecting Layer in Organic Light-Emitting Diodes
Molecular Crystals and Liquid Crystals, 2009
N-triarylamines, m-MTDAPB and 1-TNAPB, with high glass transition temperature and hole affinity were evaluated as a hole injection layer (HIL) in organic light-emitting diodes (OLEDs) with the configuration of ITO=N-triarylamine= a-NPD (HTL)=Alq 3 (EML)=LiF=Al. The performance of N-triarylamines as HIL in OLEDs was investigated in terms of turn-on voltage, luminescence, color purity, etc. Better EL performance was observed in OLED with m-MTDAPB as HIL, showing turn-on voltage of 6 V and maximum luminescence of 2,976 cd=m 2 at 13.5 V. This might be attributed to well-matched HOMO energy offsets at the interfaces of anode=HIL=HTL layers in OLED with the configuration of ITO=m-MTDAPB=a-NPD (HTL)=Alq 3 (EML)=LiF=Al, compared to OLED with 1-TNAPB as HIL.
Journal of Polymer Science Part A: Polymer Chemistry, 2010
Novel bi-triphenylamine-containing aromatic dibromide M3, N,N-bis(4-bromophenyl)-N 0 ,N 0 -dipheny-l,4-phenylenediamine, was successfully synthesized. The novel conjugated polymer P1 having number-average molecular weight of 1.31 Â 10 4 was prepared via Suzuki coupling from the dibromide M3 and 9,9-dioctylfluorene-2,7-diboronic acid bis(1,3-propanediol) ester. Polymer P1 had excellent thermal stability associated with a high glass-transition temperature (T g ¼ 141 C). The hole-transporting and UV-vis-near-infrared electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the conjugated polymer films cast onto indium-tin oxide-coated glass substrates exhibited two reversible oxidation redox couples at E 1/2 values of 0.73 and 1.13 V versus Ag/Ag þ in acetonitrile solution. The hole mobility of the conjugated polymer P1 revealed $10 À3 cm 2 V À1 s À1 , which is much higher than that of other conjugated polymer systems. The observed UV-vis-nearinfrared absorption change in the conjugated polymer film P1 at applied potentials ranging from 0.00 to 1.23 V are fully reversible and associated with strong color changes from pale yellowish in its neutral form to green and blue in its oxidized form. Using a combination of experimental study and theoretical investigation, we proposed an oxidation mechanism based on molecular orbital theory, which explains the cyclic voltammetry experimental results well. V C 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: [4654][4655][4656][4657][4658][4659][4660][4661][4662][4663][4664][4665][4666][4667] 2010
Organic Electronics, 2009
This paper describes the synthesis of three triaryldiamine derivatives presenting two thermally polymerizable trifluorovinyl ether groups that can be polymerized through thermal curing to form perfluorocyclobutyl (PFCB) polymers. These PFCB polymers, studied using time-of-flight techniques for the first time, exhibited remarkable non-dispersive holetransport properties, with values of l h of ca. 10 À4 cm 2 V À1 s À1 . When we employed these thermally polymerized polymers as hole-transport layers (HTLs) in electroluminescence devices containing tris(8-hydroxyquinolate) aluminum (Alq 3 ) as the emission layer, we obtained high current densities (ca. 3400 mA cm À2 ), impressive brightnesses (5 Â 10 4 cd m À2 ), and high external quantum efficiencies (EQEs = 1.43%). These devices exhibited the same turn-on voltage, but higher EQEs, relative to those incorporating the vacuum-processed model compound N,N 0 -di(1-naphthyl)-N,N 0 -diphenylbenzidine (a-NPD) (EQE = 1.37%) as the HTL under the same device structure.
The Journal of Physical Chemistry A, 2003
To enable the design of efficient organic electroluminescence (OLED) devices with desirable charge carrier transport properties, the mobilities of hole and electron in a series of compounds were studied computationally based on the Marcus electron transfer theory. MO calculations were performed, using the DFT B3LYP/6-31G* method in the Gaussian 98 program suite, on the following compounds: biphenyl (Bp), 4,4′biphenyldiamine (BA), triphenylamine (TPA), trip -tolylamine (TTA), 4-biphenylphenyl-m-tolylamine (BPTA), 4,4′-bis(phenyl-m-tolylamino)biphenyl (TPD), naphthalene (Np), 1-naphthyldiphenylamine (NDPA), 1-biphenylnaphthylphenylamine (BNPA), and 4,4′-bis(1-naphthylphenylamino)biphenyl (NPB). The geometries of these compounds in their neutral, cationic, and anionic states were optimized. The optimized geometries were then used to calculate the ionization potential, electron affinity, and reorganization energies. For compounds containing a biphenyl moiety (Bp, BA, BPTA, TPD, BNPA, and NPB), the interring distance and torsional angle followed the trend neutral g cationic g anionic, except NPB in which these two parameters in anionic state were larger than the corresponding parameters in the cationic state because of a small contribution from the biphenyl moiety to its LUMO. Also, the ionization potentials follow the order Bp > BPTA ≈ BNPA > BA > NPB ≈ TPD. The electron affinities were calculated to range from-1.54 to-0.05 eV for all compounds except NPB which has a positive electron affinity 0.24 eV due to the dominant contribution of two naphthyl groups to LUMO. For most compounds, the reorganization energy λ + for the hole transport is larger than λfor the electron transport except NPB and BA py (constrained nitrogen pyramidal geometry). These exceptions were rationalized by the special structures for their anionic states. According to the magnitudes of λ + , compounds can be divided into two groups: λ + g 0.28 eV (BA pl (constrained planar nitrogen geometry) ≈ Bp > TPD ≈ NPB) for compounds containing biphenyl group with or without two amino groups and λ + e 0.2 eV (TPA ≈ TTA <BPTA < BNPA ≈ NDPA) for compounds with single triarylamine group. According to the magnitudes of λ-, compounds can be divided into three groups: λg 0.50 eV (TPD > Bp > BPTA) for compounds with a dominating biphenyl group in their LUMO, λe 0.32 eV (NDPA > BNPA > Np > NPB) for compounds with a dominating naphthyl group in their LUMO, and the other compounds (TPA and TTA). From these results, λ + is determined mainly by the moiety which contributes predominantly to its HOMO, whereas λis determined mainly by the moiety which contributes predominantly to its LUMO. Therefore, by controlling the major contributors to the HOMO and LUMO, and by incorporating substituents to fine-tune the energy levels of these frontier orbitals (HOMO and LUMO), a systematic design of materials for OLED with desirable charge carrier transport properties should be feasible.
Optical Materials, 2010
We have presented 17 solution-processable linear and star-shaped imines with triphenylamine moieties. Six different amines with electron-donating or electron-withdrawing substituents and three aldehydes varying in the number of carbonyl groups have been used to study structure-optical property correlations. The unsymmetrical and symmetrical imines have been examined as a hole-transporting material (p-type) for organic light-emitting diodes (OLED)s. Current-voltage measurements were performed on ITO/compound/Alq 3 /Al devices. The lowest optical band gap value was detected at 2.12 eV. The symmetry and shape of the compounds along with the structure of the amines influenced the photoluminescence (PL) properties. Most of the obtained imines emitted blue light. The excitation wavelength and concentration of the imines also affected PL. Relative PL intensity of the imines investigated in chloroform solution was found at the range of 0.15-61% in relation to 9,10-diphenylanthracene. Melting point and glass transition temperature detected via differential scanning calorimetry (DSC) increased in the following order: unsymmetrical imines, symmetrical linear imines and star-shaped ones.
Novel hole transporting materials based on 4-(9H-carbazol-9-yl)triphenylamine derivatives for OLEDs
Molecules (Basel, Switzerland), 2014
During the past few years, organic light emitting diodes (OLEDs) have been increasingly studied due to their emerging applicability. However, some of the properties of existing OLEDs could be improved, such as their overall efficiency and durability; these aspects have been addressed in the current study. A series of novel hole-transporting materials (HTMs) 3a-c based on 4-(9H-carbazol-9-yl)triphenylamine conjugated with different carbazole or triphenylamine derivatives have been readily synthesized by Suzuki coupling reactions. The resulting compounds showed good thermal stabilities with high glass transition temperatures between 148 and 165 °C. The introduction of HTMs 3b and 3c into the standard devices ITO/HATCN/NPB/HTMs 3 (indium tin oxide/dipyrazino(2,3-f:2',3'-h)quinoxaline…