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Abstract: The Suzuki–Miyaura coupling between 3,6-dibromo-N-hexylcarbazole and aryl-boronic acids catalyzed by Pd(PPh3)4 afforded blue emitting molecules, 3,6-diaryl-N-hexylcarbazole: aryl=phenyl (1), p-methoxyphenyl (2), p-cyanophenyl (3), p-acetophenyl (4), pyrenyl (5), biphenyl (6), difluorophenyl (7) and p-nitrophenyl (8), in good yield. The HOMO level of the carbazole derivative varied between −5.67 and −6.02eV due to the electron-withdrawing or donating substituent in the aryl group. This is confirmed by the linear correlation of the Hammett parameter of the substituent in the phenyl group with oxidation potential or energy levels. Density functional theory calculation (B3LYP/6-31G*) of carbazole derivatives confirmed the experimentally observed trend. Blue fluorescence quantum yield of these molecules is high (0.19–0.96), except for the nitrophenyl derivative (<0.1). Single layer organic light emitting devices (OLEDs) using spin-coated films of 2–5 showed blue electroluminescence (EL) with a turn-on voltage at ∼6–7V. The performance of blue EL of molecules 3 and 4 improved dramatically (turn-on at ∼3V, brightness at ∼1000cd/m2, efficiency at ∼1cd/A) in a multilayer OLED designed using standard molecules as electron and hole transport layers for efficient and balanced carrier injection. [Copyright &y& Elsevier]

Abstract: N-N′-diphenyl-N,N′-(bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine) (TPD), was used to fabricate single layer devices (ITO/TPD/Ca/Al). A near-white emission (CIE coordinate of 0.25, 0.24) is observed in electroluminescence (EL) of the single layer device with prominent emission bands at 400, 475 and 670nm. Steady state and time-resolved emission spectra of spin-coated and annealed TPD films and TRES and TRANES analysis confirmed that emission at 400 and 475nm are due to monomer and excimer emission, respectively. The origin of the red emission at 670nm in EL is discussed. [Copyright &y& Elsevier]

Abstract: 3,6-diarylcarbazole derivatives, 3,6-di-(p-cyanophenyl)-N-hexylcarbazole (CNHC) and 3,6-di-(p-acetylphenyl)-N-hexylcarbazole (ANHC) were synthesized, characterized and energy levels determined. Steady state fluorescence of these molecules showed blue emission in thin films. Blends of these molecules with N,N′-diphenyl-N,N′-(bis(3-methylphenyl)-1,1′-biphenyl-4,4′-diamine (TPD) showed exciplex emission as the dominant one. Single layer organic light emitting devices (OLEDs) of CNHC, ANHC and their blends with TPD were fabricated using ITO as anode and Ca as cathode. The blend film devices showed pure exciplex electroluminescence. [Copyright &y& Elsevier]

Abstract: New heteroleptic iridium(III) complexes of 2-(p-substituted-phenyl)-pyridine were synthesized and characterized. These complexes have two cyclometalated ligands (C ∧ N) and a bidentate ancillary ligand (LX), that is, (C ∧ N)2Ir(LX). LX was either acetylacetonate or 5-nitro-8-hydroxy quinolate. Substitution on the p-phenyl of C ∧ N ligands was used to alter the electronic properties of these complexes. The (C ∧ N)2Ir(acac) complexes show phosphorescence with good quantum yields and microsecond lifetimes and also show photoluminescence over a wide visible range (λ max =503–620nm). The HOMO level and triplet energy level of these complexes were also determined. These data indicate their potential use as emitting materials for organic light emitting diodes, OLEDs. [Copyright &y& Elsevier]

The article offers information on several research related to perovskites including the metalhalide perovskite solar cells, the perovskite composition for making solar cells led by researcher Wolfgang Tress, and the promise of perovskites for light emitting devices (LEDs).