<span style="font-size:13.0pt;mso-bidi-font-size: 10.0pt;font-family:"Times New Roman";mso-fareast-font-family:"Times New Roman"; mso-ansi-language:EN-GB;mso-fareast-language:EN-US;mso-bidi-language:AR-SA" lang="EN-GB">Synthesis of new iridium complexes with substituted 1,3,4-oxadiazole and β –diketones as ligands for OLED application</span>

937-942<span style="mso-bidi-font-size:9.0pt;letter-spacing: -.1pt" lang="EN-GB">New iridium(III) complexes, viz., (OctOXD)2Ir(tta) and (OctOXD)2Ir(tmd) [OctOXD = 2-(4-butyloxyphenyl)-5-phenyl-[1,3,4]oxadiazolato-N4,C2, tta = 4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedione, tmd = 2,2,6,6-tetramethylheptane-3,5-dione] have been synthesized and characterized. These complexes have two cyclometalated ligands (C^N) and a bidentate diketone ligand {[(C^N)2Ir(X)], where X is a β-diketone with trifloromethyl, theonyl or t-butyl groups} and show good thermal stability in air up to 400 oC. The photoluminescence spectra of the two complexes show peak emissions at 537 and 557 nm, respectively. The electroluminescent properties of these complexes have been studied by fabricating multilayer devices. The electroluminescence spectra also show peak emission at 541 and 564 nm for (OctOXD)2Ir(tta) and (OctOXD)2Ir(tmd), respectively. </span

Dithieno[3,2-b:2′,3′-d]pyrrole–alkylthiophene–benzo[c][1,2,5]thiadiazole-based highly stable and low band gap polymers for polymer light-emitting diodes

A series of new low band gap π-conjugated polymers containing N-alkyldithieno[3,2-b:2′,3′-d]pyrrole, benzo[c][1,2,5]thiadiazole, and alkylthiophenes are reported. The polymerization condition was standardized and the use of CuO to obtain high-molecular-weight polymer was also realized. The molecular weight of the polymers was found to be in the range of 45,000–53,000. All the polymers were found to be soluble in most of the common organic solvents, such as chloroform, dichloromethane, THF, and chlorobenzene with excellent film forming properties. The λmax of the polymers was found to be in the range of 687–663 nm with band gap in the range of 1.35–1.43 eV. The oxidation potential of the polymers from cyclic voltammetry was determined to be 0.5–0.75 V. The HOMO levels of the above synthesized polymers were found to be between 5.24 and 5.54 eV. All the polymers exhibited a PL emission in between 755 and 773 nm. The polymers were found to be thermally stable above 277 °C with only a 5% weight loss. From the thermal stability values, it is expected that the current set of polymers are stable enough for the application in electronic devices. To realize the potential use of the polymers, EL devices were fabricated and found to show red emission with comparatively low threshold voltage. A brightness of 54 cd m−2 for the device with polymer PC could be reached

Synthesis and characterization of 5,7-dimethyl-8-hydroxyquinoline and 2-(2-pyridyl)benzimidazole complexes of zinc(II) for optoelectronic application

Bis(5,7-dimethyl-8-hydroxyquinolinato)zinc(II) (Me2q)2Zn and 5,7-dimethyl-8-hydroxyquinolinato(2-(2-pyridyl)benzimidazole) zinc(II) Me2q(pbi)Zn have been synthesized and characterized by various techniques. These metal complexes have high thermal stability (>300 °C) and high glass transition temperatures (>150 °C). The vacuum deposited films of these materials show good film forming property and are suitable for opto-electronic applications. Multilayered organic electroluminescent (EL) devices have been fabricated having structure ITO/α-NPD/zinc complex/BCP/Alq3/LiF/Al, which produce emission with chromaticity having Commission Internationale d’Eclairage (CIE) coordinates x = 0.506 and y = 0.484 for (Me2q)2Zn; x = 0.47 and y = 0.52 for (Me2q)(pbi)Zn complex. The electroluminescence spectra show peak emission centered at 572 and 561 nm respectively for these materials

Hyperbranched Poly(arylene ethynylene)s with Triphenylamine Core for Polymer Light-Emitting Diodes

A series of light-emitting hyperbranched poly(arylene ethynylene)s (HB-PAEs) were prepared by the Sonogashira coupling from bisethynyl of carbazole, fluorene, or dialkoxybenzenes (A2 type) and tris(4-iodophenyl)amine (B3 type). For comparison, two linear polymers (L-PAEs) of the HB analogs were also synthesized. The polymers were characterized by Fourier transform infrared, NMR, and GPC. The HB polymers showed excellent solubility in chloroform, THF, and chlorobenzene when compared with their linear analogs. The number-average molecular weight (Mn) of the polymers determined from GPC was found to be in the range of 18,600–34,200. The polymers were thermally stable up to 298–330 °C with only 5% weight loss. The absorption maxima of the polymers were between 354 and 411 nm with optical band gap in the range of 2.5–2.9 eV. The HB polymers were found to be highly fluorescent with photoluminescence quantum yields around 33–42%. The highest occupied molecular orbital energy levels of the polymers calculated from onset oxidation potentials were found to be in the range from −5.83 to −6.20 eV. Electroluminescence (EL) properties of three HB-PAEs and one L-PAE were investigated with device configuration ITO/PEDOT:PSS/Polymer/LiF/Al. The EL maxima of HB-PAEs were found to be in the range of 507–558 nm with turn-on voltages around 7.5–10 V and maximum brightness values of 316–490 cd/m2. At the same time, linear analog of one HB-PAE was found to show a maximum brightness of 300 cd/m2 at a turn-on voltage of 8.2 V

n-Type ternary zinc complexes: Synthesis, physicochemical properties and organic light emitting diodes application

We report synthesis, characterization and use of ternary zinc complexes as emissive and electron transport material in organic light emitting devices (OLED). 5,7-Dimethyl-8-hydroxyquinoline or 2-carbonitrile-8-hydroxyquinoline have been used with 2-(2-hydroxyphenyl)benzoxazole to synthesize (2-(2-hydroxyphenyl)benzoxazolato) (5,7-dimethyl-8-hydroxyquinolinato)zinc(II) [Zn(HPB)(Me(2)q)] and (2-(2-hydroxyphenyl) benzoxazolato)(2-carbonitrile-8-hydroxyquinolinato)zinc(II) [Zn(HPB)(CNq)] complexes. These complexes possessed high thermal stability and having good film forming property. Optical properties of the synthesized complexes have been studied by UV-visible absorption, photoluminescence and time resolved photo-luminescence spectroscopy. Density functional theoretical calculations have been performed to demonstrate the three-dimensional geometries and the frontier molecular orbital energy levels of these compounds. Synthesized materials show quite good efficiency in multilayered device structure ITO/alpha-NPD/Zinc complex/BCP/Alq(3)/LiF/Al with maximum brightness of 7017 cd/m(2) and 6925 cd/m(2) having electroluminescence spectral peak emission centered at 567 nm and 569 nm, respectively. Electron mobility of these molecules were found to be 1.5 x 10(-6)-1.2 x 10(-5) cm(2)/V s for electric field range 1000-1200 (V/cm)(1/2) and hence showed very high efficiency as electron transport layer in device structure ITO/alpha-NPD/5% Ir(ppy)(3) doped CBP/BCP/Zn(HPB)(Me(2)q) or Zn(HPB)(CNq)/LiF/Al

Synthesis and characterization of alternative donor–acceptor arranged poly(arylene ethynylene)s derived from 1,4-diketo-3,6-diphenylpyrrolo[3,4-c]pyrrole (DPP)

A series of donor–acceptor type poly(arylene ethynylene)s (PAEs) have been synthesized through Sonogashira polycondensation. The polymers consist of an electron donating 9,9-bis(2-ethylhexyl)-9H-fluorene, triphenylamine, 1,4-dialkoxybenzene or 9-(2-ethylhexyl)-9H-carbazole unit and an electron accepting 2,5-bis(2-ethylhexyl)-3,6-diphenylpyrrolo[3,4-c]pyrrole-1,4(2H,5H)-dione (EH-DPP) unit, alternately connected through ethynyl bridge. The polymers exhibit weight-average molecular weights (Mw) up to 68, 500 and are soluble in chlorobenzene, dichlorobenzene, THF, chloroform and toluene. A brilliant red solution with absorption maxima between 491 and 500 nm was observed for all the polymers. An intense red fluorescent with photoemission maxima between 551 and 571 nm was observed from polymer solutions. The polymers showed good thermal stability with decomposition temperature more than 260 °C at 5% weight loss. Onset oxidation potentials of the polymers were observed between 1.30 and 1.58 V with HOMO energy levels in the range of −6.10 to −6.38 eV. The OLED devices were fabricated with configuration of ITO/PEDOT:PSS/polymer/LiF/Al for all the polymers and EL maxima between 666 and 684 nm were observed

Synthesis, Characterization, and Electroluminescent Characteristics of Mixed-Ligand Zinc(II) Complexes

Mixed-ligand zinc complexes, i.e., 2-(2-hydroxyphenyl)benzothiazolato-5,7- dichloro-8-hydroxyquinolinato zinc(II) [ZnBTZ(Cl(2)q)], 2-(2-hydroxyphenyl) benzothiazolato-5,7-dimethyl-8-hydroxyquinolinato zinc(II) [ZnBTZ(Me(2)q)], and 2-(2-hydroxyphenyl)benzothiazolato-2-carbonitril-8-hydroxyquinolinato zinc(II) [ZnBTZ(CNq)], were synthesized and characterized. The metal complexes have high thermal stability (> 300A degrees C) and high glass-transition temperature (> 150A degrees C) and are suitable for optoelectronic applications. Optical properties of the synthesized complexes were characterized by using ultraviolet-visible (UV-Vis) and photoluminescence spectroscopy. Color tuning by changing the ligand was observed in synthesized complexes. Multilayered organic electroluminescent devices were fabricated having structure indium-tin oxide (ITO)/N,N'-diphenyl-N,N'-bis(1-naphthyl)-1,1'-biphenyl-4,4'-diamine (alpha-NPD)/zinc complex/2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP)/tris(quinolinolate)Al-III (Alq(3))/LiF/Al using the synthesized complexes as emissive material. The electroluminescence spectra show peak emission centered at 532 nm, 572 nm, and 541 nm, respectively, for these materials. The emitted light has chromaticity with Commission Internationale d'A parts per thousand clairage coordinates x = 0.35 and y = 0.56 for ZnBTZ(Cl(2)q), x = 0.49 and y = 0.47 for ZnBTZ(Me(2)q), and x = 0.48 and y = 0.40 for ZnBTZ(CNq) complex

White organic light emitting diodes based on DCM dye sandwiched in 2-methyl-8-hydroxyquinolinolatolithium

Stable white electroluminescence (EL) has been achieved from organic LED, in which an ultrathin 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl-aminostyryl)-4H-pyran (DCM) dye layer has been inserted in between two 2-methyl-8-hydroxyquinolinolatolithium [LiMeq] emitter layer and by optimizing the position of the DCM dye layer from the α-NPD/LiMeq interface. Electroluminescence spectra, current–voltage–luminescence (I–V–L) characteristics of the devices have been studied by changing the position of the dye layer. As the distance of DCM layer from α-NPD/LiMeq interface is increased, the intensity of host emission enhances rapidly. Introduction of thin layer of DCM in emissive layer increases the turn on voltage. The best Commission International de L’ Eclairage (CIE) coordinates i.e. (0.32, 0.33) were obtained with device structure ITO/α-NPD(30 nm) /LiMeq(10 nm)/DCM(1 nm)/LiMeq(25 nm)/BCP(6 nm)/Alq3(28 nm)/LiF(1 nm)/Al(100 nm). The EL spectrum covers the whole visible spectra range 400–700 nm. The color rendering index (CRI) for our best white light (Device 4) is 47.4. The device shows very good color stability in terms of CIE coordinates with voltages. The maximum luminescence 1240 cd/m−2 has been achieved at 19 V