A study of thermal,optical and electrical properties of new branched triphenylamine-based polyazomethines

A series of branched aromatic polyazomethines have been obtained by high temperature solution polycondensation of 4,4′,4″-triformyltriphenylamine with 3,3′-dimethoxybenzidine with different feed molar ratio. For three polymers additional condensation of chain end groups with monofunctional monomers such as 4-formyltriphenylamine or 2-naphthylamine was carried out. Moreover, two model compounds were prepared and investigated for comparison with branched polymers. The structures of polymers and models were characterized by means FTIR, ¹H, ¹³C NMR spectroscopy, elemental analysis and gel permeation chromatography (GPC). UV–vis properties of the thin films of the polymers and compounds were investigated on the glass substrate. Eg of the branched polymers was found about 2.47 eV. UV–vis and FTIR spectroscopy for iodine doped compounds were investigated. Doping decreased the value of Eg of the branched polyazomethines to about 1.71 eV. Refractive index (n) for branched polyazomethines was found about 1.97, while for the doped compounds was a little higher (～2.48). Absorption (UV–vis) properties of the doped with iodine branched imines were investigated additionally after heating in different temperatures from 50 to 200 °C. Intensity of photoluminescence of branched imines in relation to 9,10-diphenylanthracene was found in the range 0.2–1.0% and 2.7–43.7% in dependence on the excitation wavelengths. Current–voltage (I–V) measurements were performed on ITO/TiO₂/polymer/Al, ITO/polymer/Alq₃/Al and ITO/TiO₂/polymer/Alq₃/Al devices in the dark and during irradiation with light (under illumination 1000 W/m²). The sol–gel technique was applied to prepared TiO₂ layer. TiO₂ layers and devices were investigated by Atomic Force Microscopy (AFM). Moreover, properties of these branched polymers were compared with the linear polyazomethine based on 3,3′-dimethoxybenzidine and 4,4′-diformyltriphenylamine.     

Aliphatic–aromatic poly(azomethine)s with ester groups as thermotropic materials for opto(electronic) applications

We have explored the opto(electronic) and liquid crystal properties of a new series of semiconducting materials based on aliphatic–aromatic poly(azomethine)s. The structures of polymers were characterized by means of FTIR, ¹H, ¹³C NMR spectroscopy, and elemental analysis. UV–vis properties of the thin films of the polymers were investigated on the quartz substrate. The lowest optical energy gap (E_g) at 2.28 eV was found. The polymers were irradiated with a test dose of 2 Gy Co-60 gamma-rays to detect their thermoluminescence properties in the temperature range 25–200 °C. Mesomorphic behavior was investigated via differential scanning calorimetry (DSC) and polarizing optical microscopy (POM) studies. Being into consideration backbone geometry, all polymers, excepted polymer PAZ2, obtained from poly(1,4-butanediol)bis(4-aminobenzoate) and 9-(2-ethylhexyl)carbazole-3,6-dicarboxaldehyde, exhibited liquid-crystalline properties. Moreover, the electrical characterizations of bulk heterojunction (BHJ) and bilayer devices with the following architecture ITO/PEDOT/PAZ:TiO₂/Al were investigated. Additionally, devices without and with TiO₂ layer such as ITO/PAZ/Al and ITO/TiO₂/PAZ/Al were prepared and investigation in the dark and during irradiation with light (under illumination 1000 W/m²). The sol–gel technique was applied to prepared TiO₂ layers and powders. Moreover, impedance spectroscopy at different temperatures for electrical properties measurement was used. Additionally, the compounds were tested using various AFM techniques such as Mode and Phase Imaging and local contrast force–distance curve measurement and roughness (Ra, Rms) along with skew and kurtosis are presented.     

Highly efficient energy transfer to a novel organic dye in OLED devices

The neutral 4,4-difluoro-8-(2,2′:6′,2″-terpyridine-4′-yl)-1,3,5,7-tetramethyl-2,6-diethyl-4-bora-3a,4a-diaza-s-indacene (Boditerpy) molecule was synthesized and incorporated as dopant (<1%) in double-layer organic light emitting diodes (OLEDs) with the configuration ITO/α-NPD(60 nm)/Alq₃(60 nm):Boditerpy (0.4 nm)/LiF(0.02 nm)/Al(80 nm). This device exhibits green emission with a brightness of 545 cd/m² at 8 V and a maximum power efficiency of 0.9 lm/W. A full quantitative energy transfer process is indicated by a complete quenching of light emission from Alq₃ in photoluminescence. However, I–V characteristics indicate some losses during the charge transfer processes in OLED configuration     

Organic light-emitting device using new distyrylarylene host materials

Novel distyrylarylene-based blue host materials, 4,4′-bis(1,2-diphenylvinyl)-p-terphenyl (2), 4,4′-bis[1-phenyl-2-(p-tolyl)vinyl]-p-terphenyl (3) and 4,4′-bis[1-phenyl-2-(4,4′-biphenyl)vinyl]-p-terphenyl (4) were successfully synthesized using 4,4′-bisbenzoyl-p-terphenyl (1) through Wittig–Hornor reaction and a blue organic light-emitting diode (OLED) was made from them. The structure of the blue device is ITO/DNTPD/NPB/Host:DSA-Ph/Alq₃/Al-LiF. Here, NPB is used as a hole transport layer, DNTPD as the hole injection layer, DSA-Ph as the blue dopant, Alq₃ as the electron transport layer and Al as the cathode. The blue device doped with 5%-DSA-Ph shows a blue EL spectrum at 463 nm and a high efficiency of 4.14–5.13 cd/A.     

A blue organic emitting diode derived from new styrylamine type dopant materials

We have designed and synthesized new dopant materials based on the styrylamine moiety, 4-[(1,2-diphenyl)-4′-(N,N-diphenyl-4-vinylbenzenamine)]biphenyl (4) and 4-[(1,2-diphenyl)-4′-(N,N-diphenyl-4-vinylbenzenamine)]terphenyl (8). Blue OLEDs were obtained from new styrylamine dopant materials and compared with those of blue dopant bis[4-(di-p-N,N-diphenylamino)styryl]stilbene (DSA-Ph) and diphenyl[4-(2-terphenyl vinyl)phenyl]amine (R-BD). The ITO/DNTPD/NPB/MADN:dopant/Alq₃/Al-LiF device obtained from 4 shows blue EL spectrum at 469 nm and high efficiency 3.02 cd/A at 7 V. 8 also shows blue EL spectrum around λ_max = 468 nm, efficiency of 3.51 cd/A and a current density of 25.94 mA/cm² (855.7 cd/m²) at 7 V.     

Transient electroluminescence in organic alloy light emitting diodes

In this paper, we report on transient electroluminescence (EL) studies in (ITO/TPD/alloy/Alq₃/Al) organic light emitting diodes. The alloy in the active layer is a co-evaporated mixture of TPD + Alq₃ in the ratio TPD:Alq₃ = 1:4. These results were compared with the transient EL response of a standard device (ITO/TPD/Alq₃/Al). The EL response of the alloy device consists of two components – a fast component (10–20 μs) and a slow component (200–300 μs). It is shown that the slow component arises due to the leakage of electrons from the Alq₃ layer into the alloy layer and subsequent exciton formation in the alloy layer. The magnitude of the fast component depends on the pulse repetition rate and temperature. This is shown to be related to the presence of deep traps in the alloy layer. The presence of deep traps is also confirmed by current transients in the alloy device.     

Synthesis,photoluminescent and electroluminescent properties of a novel europium(III) complex involving both hole- and electron-transporting functional groups

A novel europium(III) complex involving a carbazole fragment as hole-transporting group and an oxadiazole fragment as electron-transporting group was synthesized and used as red light-emitting material in organic light-emitting diodes (OLEDs). The complex is amorphous, and exhibits high glass transition temperature (T_g = 157 °C) and high thermal stability with a 5% weight loss temperature of 367 °C. Two devices, device 1: ITO/NPB (40 nm)/Eu(III) complex (30 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al (100 nm) and device 2: ITO/NPB (40 nm)/3% Eu(III) complex: CBP (30 nm)/BCP (10 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al (100 nm), were fabricated, where NPB is N,N′-di(naphthalene-1-yl)-N,N′-diphenyl-benzidine, Alq₃ is tris(8-hydroxyquinoline) Al(III), CBP is 4,4′-bis(carbazole-9-yl)-biphenyl, and BCP is 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, respectively. In contrast with device 1, owing to less self-quenching and better charge confinement, device 2 shows improved performances: the maximum luminance of device 2 was dramatically increased from 199 to 1845 cd/m², the maximum current efficiency was increased from 0.69 to 2.62 cd/A, the turn-on voltage was decreased from 9.5 to 5.5 V, and higher color purity was attained.     

Phenothiazine conjugated bipyridine as ancillary ligand in Ru(II)-complexes for application in dye sensitized solar cell

A new high molar extinction coefficient ruthenium(II)-bipyridine complex “cis-Ru(4,4′-bis((E)-2-(10-decyl-10H-phenothiazin-3-yl)vinyl)-2,2′-bipyridine)(4,4′-dicarboxylic acid-2,2′-bipyridine)(NCS)₂ PTZ1″ was synthesized through conjugation of phenothiazine unit with bipyridine and characterized by FT-IR, ¹H-NMR and ESI-MASS spectroscopes. Absorption measurements and time dependent-density functional theory (TD-DFT) calculations show increased spectral response for the ancillary ligand and the corresponding complex. The dye upon anchoring onto mesoporous nanocrystalline TiO₂ solar cells exhibited solar-to-electric energy conversion efficiency (η) of 3.77% short-circuit photocurrent density (J_SC) = 7.79 mA/cm², open-circuit voltage (V_OC) = 640 mV, fill factor = 0.750) under air mass 1.5 sunlight, the reference Z907 and HRS1sensitized solar cells, fabricated and evaluated under identical conditions exhibited η-value of 7.02% (J_SC = 15.25 mA/cm², V_OC = 650 mV, fill factor = 0.705) and 3.05% (J_SC = 8.20 mA/cm², V_OC = 610 mV, fill factor = 0.620) respectively. The lower film absorption of PTZ1on TiO₂ surface could be probably due to larger molecular diameter and planarity of phenothiazine prone to aggregate in solution as well as on TiO₂ surface. The DFT calculations show that the first three HOMOs of PTZ1 have t2g character as observed in case of Z907, while HOMO-4 and HOMO-5 have π-orbitals with major component on phenothiazine moieties of L1.     

Synthesis,spectroscopy and electroluminescence of cadmium(II) polypyridyl complexes

Five new complexes [Cd(ptpy-R)₂](PF₆)₂ (ptpy = 4′-phenyl-2,2′:6′,2″-terpyridine; R = tert-Butyl (1), hexyloxy (2), carbozole-9-yl (3), naphthalene-1-yl-phenylamine-N-yl (4) and diphenylamine-N-yl (5)) were synthesized and characterized by ¹H NMR, elemental analyses, UV–vis spectroscopy and cyclic voltammetry. The emission color of resultant complex molecules has been tuned effectively, from violet (397 nm) for 1 to orange (602 nm) for 5 in film, by modifying the electron-donating ability of the substituent R. The UV–vis spectroscopy and the solution-state luminescence showing remarkable solvatochromism suggests the emission involves the intra-ligand charge transfer (¹ILCT) excited state, occurring from the substituent R moiety to Cd(II) coordinated terpyridine. The electroluminescence (EL) properties for these organic materials were also studied and complexes 3, 4 and 5 exhibit EL wavelength at 548 nm, 596 nm and 604 nm with maximum current efficiency of 3.25 cd/A, 3.15 cd/A and 2.16 cd/A, respectively.     

Low voltage organic light emitting diode using p–i–n structure

Efficient n-type doping has been achieved by doping Liq in electron transport material Alq₃. Detailed investigation of current density–voltage characteristics of electron only devices with different doping concentrations of Liq in Alq₃ has been performed. An increase in current density by two orders of magnitude has been achieved with 33 wt% of Liq doped in Alq₃. Organic light emitting diode with p–i–n structure was fabricated using F₄-TCNQ doped α-NPD as hole transport layer, Ir(ppy)₃ doped CBP as emitting layer and 33 wt% Liq doped Alq₃ as electron transport layer. Comparison of OLEDs fabricated using undoped Alq₃ and 33 wt% Liq doped Alq₃ as electron transport layer shows reduction in turn on voltage from 5 to 2.5 V and enhancement of power efficiency from 5.8 to 10.6 lm/W at 5 V.     

Highly efficient red electroluminescence induced by efficient electron injection and exciton confinement

Highly efficient DCJTB-doped device was realized by enhanced electron injection and exciton confinement. A fluorine end-capped linear phenylene/oxadiazole oligomer 2,5-bis(4-fluorobiphenyl-4′-yl)-1,3,4-oxadiazole (1) and a trifluoromethyl end-capped oligomer 2,5-bis(4-trifluoromethylbiphenyl-4′-yl)-1,3,4-oxadiazole (2) were designed and incorporated as an electron transporting/hole blocking material in the device structure ITO/NPB (60 nm)/DCJTB:Alq₃ (0.5%, 10 nm)/1 or 2 (20 nm)/Alq₃ (30 nm)/LiF (1 nm)/Al (100 nm). The devices showed highly efficient red luminescence. In particular, the device based on 1 achieved pure red luminescence at 620 nm originating from DCJTB, with a narrow FWHI of 65 nm, maximal brightness of 13,300 cd/m² at voltage of 20.8 V and current density of ca. 355 mA/cm². High current and power efficiencies (>3.6 cd/A, 1.0 lm/W) were retained within a wide range of current densities. Our results show efficient and stable DCJTB-doped red electroluminescence could be anticipated for practical applications by taking advantage of the present approaches. The control experiments using BCP were also studied.     

Synthesis,optical and electrochemical properties of novel hole-blocking poly(biphenylene-1,3,4-oxadiazole) containing electron-withdrawing trifluoromethyl groups

New poly(biphenylene-1,3,4-oxadiazole) P1 and poly(biphenylene hydrazide) P2 containing electron-withdrawing trifluoromethyl group at the 2 and 2′ positions of biphenyl moiety were synthesized. The biphenyl is forced to adapt a non-coplanar conformation due to the bulky trifluoromethyl group. High quality polymer P1 thin film can be easily obtained by thermal cyclodehydration from its soluble polyhydrazide precursor P2. The polymer P1 exhibited good thermal stability with glass transition temperature of 234 °C and 5% decomposition temperature of 469 °C. The optical and electrochemical properties were investigated by UV–vis spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. For polymer P1 film, two absorption peaks at 370 and 414 nm were observed. It also exhibited a photoluminescent peak at 555 nm when excited by 414 nm light. The cyclic voltammetric studies revealed that polymer P1 had extremely low HOMO (?6.85 eV) and LUMO (?3.71 eV) energy levels due to the presence of strong electron-withdrawing trifluoromethyl group. It also exhibited a large energy gap (3.14 eV) which is an indication of short conjugation length resulted from non-coplanar biphenyl structure. Its HOMO energy was even lower than that of widely used hole-blocking material, 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole PBD (?6.30 eV). The low LUMO energy of polymer P1 could allow the easier electron injection from air-stable cathode such as aluminum. The good electron transfer ability was also shown by measuring the current density of electron-only devices with the structures of Al/P1 (150 nm)/Alq₃ (50 nm)/Al and Al/Alq₃ (200 nm)/Al. Combined with high thermal stability and amorphous morphology, polymer P1 would be a promising candidate as the hole-blocking material for organic light-emitting diodes.     

Synthesis and characterization of pentacene derivative by Wittig–Horner reagent and its composite with nano-sized TiO2

Wittig–Horner reagent was firstly used to prepare a pentacene derivative which was designated as 6-phenylidene-13,13-dihydropentacene (PHP). The newly prepared derivative was more soluble than pentacene due to the introduction of substituted group. UV–vis spectra showed that it displayed a wide absorption in the range of 470–650 nm in CHCl₃, and with a maximum absorption at 555 nm. In cyclic voltammetry (CV) test, it was found that its forbidden band gap was as small as 1.34 eV. During the photo-oxidation test, the as-prepared pentacene was sensitive to ambient light but sluggish to air in solution. Moreover, a composite of PHP–TiO₂ was also constructed. A series of characterizations proved that an interaction between PHP and TiO₂ most probably had occurred, leading to generation of some novel properties which were different from both PHP and TiO₂. The most interesting result is that the band gap of the composite material is smaller than that of PHP and TiO₂, with the value of 1.18 eV.     

Photoluminescence and electroluminescence of 3-methyl-8-dimethylaminophenazine

A new phenazine dye—3-methyl-8-dimethylaminophenazine (MDAP) with intramolecular charge transfer (ICT) property was synthesized. The photoluminescence and electroluminescence of were investigated. The device with a configuration of ITO/TPD (30 nm)/TPD:MDAP (30 nm)/Alq₃:MDAP (35 nm)/Alq₃ (30 nm)/Mg:Ag (200 nm) showed a good performance with a brightness of 21650 cd/m² at 250 mA/cm², a maximum luminous efficiency of 9.97 cd/A and a yellow emission peaked at about 564–586 nm.     

Synthesis and characterization of novel 2,5-diphenyl-1,3,4-oxadiazole derivatives of anthracene and its application as electron transporting blue emitters in OLEDs

With a general aim to make anthracene derivatives multifunctional (n-type emitter) and also study their suitability as electron transport layers for organic light emitting diodes (OLED), we report the synthesis and characterization of five novel molecules in which the 9 and 10 positions of anthracene have been directly substituted by 2,5-diphenyl-1,3,4-oxadiazole groups. We have carried out detailed characterization of these molecules which include photophysical, electrochemical, thermal, electroluminescent and computational studies. The electron affinity is very high, around 3.7 eV, and the ionization potential is around 6.7–6.8 eV, which is relatively higher than the most commonly used electron transport electroluminescent layer Alq₃. The studies reveal that the new molecules being reported by us, in addition to the high thermal stability, are quite efficient in a two layer unoptimized nondoped device with the device structure ITO/α-NPD/10a–11b/LiF/Al and have an emission in pure blue. They also show very high efficiency as electron transport layer in device structure ITO(120 nm)/α-NPD(30 nm)/Ir(ppy)₃ doped CBP(35 nm)/BCP(6 nm)/10a(28 nm)/LiF(1 nm)/Al(150 nm). From these studies we conclude that these anthracene derivatives also have considerable potential as multifunctional layers and as electron transport layers in OLED.     

Manufacture of brightness enhancement films (BEFs) by ultraviolet (UV) irradiation and their applications for organic light emitting diodes (OLEDs)

By ultraviolet (UV) irradiation, brightness enhancement films (BEFs) have been successfully manufactured with UV-curable polymers and applied for organic light emitting diodes (OLEDs).With BEFs, either green OLEDs (BEF/ITO glass/NPB (30 nm)/Alq₃ (65 nm)/LiF (0.5 nm)/Al (100 nm)) or white OLEDs (BEF/ITO glass/TAPC (40 nm)/mCP:Os:Firpic mixture (weight ratio = 82:17:1; 25 nm)/BCP (15 nm)/Alq₃ (30 nm)/LiF (0.5 nm)/Al(150 nm)) exhibit better electroluminescent performances than those without BEFs. In case of green OLEDs, the luminance and electroluminescent yield with 45° compound BEFs are, respectively, 1.51-fold and 1.42-fold (at 9 V, 60 mA/cm²) larger than those without BEFs. In case of white OLEDs, moreover, the luminance and electroluminescent yield with 45° compound BEFs are, respectively, 1.28-fold and 1.21-fold (at 9 V, 16 mA/cm²) larger than those without BEFs.     

Effect of TiO2 on thermal,structural and third-order nonlinear optical properties of Ca–La–B–O glass system

A series of calcium lanthanum metaborate glasses in the composition (wt%) of 23.88CaO–28.33La₂O₃–47.79B₂O₃ modified with TiO₂ up to 20 wt% are prepared by a melt quenching technique to study the influence of TiO₂ on their thermal, structural, linear and nonlinear optical properties. The differential thermal analysis (DTA) studies have demonstrated significant effects due to the presence of TiO₂ on the glass forming ability and crystallization situations. The glass with 15 wt% TiO₂ has achieved a eutectic composition and also exhibited a better glass forming ability among the glasses studied. The FT-IR spectra of these glasses show mainly vibration modes corresponding to stretching of BO₃ trigonal, BO₄ tetrahedral units and of B–O–B bending bonds. At higher concentrations of TiO₂, development of vibration band around 400 cm^?1 has indicated the formation of TiO₆ structural units in the glass network. The red shift of optical absorption edge (UV cutoff) shows a monotonous decrease in direct and indirect optical band gap energies (E_opt) with an increase of TiO₂ content in the glasses based on their absorption spectra. The optical transparency of these glasses is found to be varied from 64 to 87% within the wavelength range 450–1100 nm depending on the TiO₂ content. Besides these studies, linear refractive indices, the nonlinear optical properties of these glasses have also been evaluated.     

Polypyridyl Ru(II)-sensitizers with extended π-system enhances the performance of dye sensitized solar cells

New polypyridyl ruthenium(II) complexes “cis-Ru(4,4′-dimesityl-2,2′-bipyridine) (Ln) (NCS)₂ H102” and “cis-Ru(4,4′-bis(2,3,6-tri-isopropylphenyl)-2,2′-bipyridine) (Ln) (NCS)₂ H105”, where Ln = 4,4′-dicarboxylic acid-2,2′-bipyridine; were synthesized and successfully applied to sensitization of nano-crystalline TiO₂ based solar cells (DSSCs). The DSSCs of H102 and H105 fabricated from 0.16 cm² TiO₂ electrodes exhibited broader comparable photocurrent action spectra with almost identical solar-to-electrical energy conversion efficiency (η) as compared to N719 sensitizer. The incident photon-to-current conversion efficiency (IPCE) values of 98% and 95% were obtained for H102 and H105 sensitizers respectively. Under 1 sun condition, η-values of 8.39% (short-circuit photocurrent (J_SC) = 16.4 mA/cm², open-circuit photo voltage (V_OC) = 692 mV, fill factor = 0.734), 8.76% (J_SC = 16.3 mA/cm², V_OC = 735 mV, fill factor = 0.734) and 9.12% (J_SC = 16.1 mA/cm², V_OC = 745 mV, fill factor = 0.753) were obtained for H102, H105 and N719 sensitizers respectively.     

Low band gap copolymer containing naphthalene-1,4,5,8-tetracarboxylic bisimide: Synthesis,properties and organic solar cell applications

A new alternating donor–acceptor copolymer, poly{[2,7-(9,9′-dioctylfluorene)-alt-5,5′-(bis(2,2′-thiophene)-4,7-(2,1,3-benzothiadiazole)]-co-[2,7-(9,9′-dioctylfluorene)-alt-5,5′-(bis(2,2′-thiophene)-2,6-naphthalene-1,4,5,8-tetracarboxylic-N,N′-di(2-ethylhexyl)imide]} (PFTBTN), was synthesized for the use of photovoltaic cells. The copolymer containing fluorene, as the donor segment and naphthalene bisimide, dithienylbenzothiadiazole, as the acceptor segment was polymerized via Suzuki couplings to achieve a polymer with a narrow band gap. The band gap values of the copolymer film determined from optical and electrochemical measurements were 1.69 and 2.06 eV, respectively. The optical absorption spectrum revealed two broad bands in the range of 300–750 nm. Electrochemical studies indicate sufficiently deep HOMO/LUMO levels that enable a high open-circuit voltage when fullerene derivative ([6,6]-phenyl-C₆₁ butyric acid methyl ester) was used as an electron acceptor. Bulk heterojunction photovoltaic cells were fabricated in the device configuration of ITO/PEDOT:PSS/PFTBTN:PCBM/TiO_x/Al. Open-circuit voltage reached 0.74 V with the maximum energy conversion efficiency of 0.40% under the illumination of AM 1.5 (100 mW/cm²).     

Synthesis and hole-transporting properties of vinyl-type polynorbornenes with ethyl ester linked triarylamine side groups

Palladium(II)-catalyzed polymerization of norbornene monomers bearing triarylamine side groups was investigated to prepare the vinyl-type polynorbornenes having hole-transporting properties. Norbornene monomers (M1–M3) with the ethyl ester linked aryldiphenylamines where the aryl group is phenyl, m-tolyl, and 1-naphthyl, respectively, were employed. The combined use of the Pd(II) catalyst supported by N-heterocyclic carbene ligand and AgSbF₆ leads to the production of soluble polynorbornenes (P1–P3). While the cyclic voltammetry measurements show the relatively low oxidational stability of polymers, the polymers exhibit the high glass transition temperature of 305–333 °C. The atomic force microscopy images of the thin film of P1 reveal the very smooth film surface with a roughness of 0.29 nm, indicating the good film-forming capability of polymer. When incorporated as a hole-transporting layer in Alq₃-based electroluminescent devices, the spin-coated polymer films display hole-transporting property suitable for the proper green emission of Alq₃. Among the devices studied, the one based on 1-naphthylamine-containing P3 exhibits the highest performance in terms of luminance and external quantum efficiency.