We demonstrate very high efficiency electrophosphorescence in organic light-emitting devices employing a phosphorescent molecule doped into a wide energy gap host. Using bis(2-phenylpyridine)iridium(III) acetylacetonate [(ppy)2Ir(acac)] doped into 3-phenyl-4(1′-naphthyl)-5-phenyl-1,2,4-triazole, a maximum external quantum efficiency of (19.0±1.0)% and luminous power efficiency of (60±5) lm/W are achieved. The calculated internal quantum efficiency of (87±7)% is supported by the observed absence of thermally activated nonradiative loss in the photoluminescent efficiency of (ppy)2Ir(acac). Thus, very high external quantum efficiencies are due to the nearly 100% internal phosphorescence efficiency of (ppy)2Ir(acac) coupled with balanced hole and electron injection, and triplet exciton confinement within the light-emitting layer.

Nearly 100% internal phosphorescence efficiency in an organic light emitting device

Organic–inorganic hybrid perovskite materials are attracting great interest for their applications in photovoltaics where they have demonstrated excellent efficiency. Here, Dou et al. demonstrate room temperature, solution-processed hybrid perovskite photodetectors with fast response and high detectivity.

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Solution-processed hybrid perovskite photodetectors with high detectivity

A comprehensive review of the literature on electron transport materials (ETMs) used to enhance the performance of organic light-emitting diodes (OLEDs) is presented. The structure−property−performance relationships of many classes of ETMs, both small-molecule- and polymer-based, that have been widely used to improve OLED performance through control of charge injection, transport, and recombination are highlighted. The molecular architecture, electronic structure (electron affinity and ionization potential), thin film processing, thermal stability, morphology, and electron mobility of diverse organic ETMs are discussed and related to their effectiveness in improving OLED performance (efficiency, brightness, and drive voltage). Some issues relating to the experimental procedures for the estimation of relevant material properties such as electron affinity and electron mobility are discussed. The design of multifunctional electroluminescent polymers whereby light emission and electron- and hole-transport pro...

Electron Transport Materials for Organic Light-Emitting Diodes

Most present-day semiconductor devices use inorganic crystalline materials, with single-crystalline silicon dominating other materials like GaAs by about a factor of 1000. Despite the advantages of single-crystalline inorganic semiconductors like high room-temperature mobility (up to 1000 cm2/(V s)) and high stability, these materials are less suitable for low-cost and large-area applications. Additionally, silicon is an indirect semiconductor and therefore is not well suited for optoelectronic applications like light-emitting diodes. Solar cells from silicon are expensive and require a large amount of energy for their fabrication, leading to a long energy payback time. As an alternative, organic semiconductors have recently gained much attention (for review articles, see refs 1 -3 (OLEDs), ref 4 (organic electronics in general), and refs 5 and 6 (organic solar cells)). Originally, much of the research concentrated on single crystals, which can have mobilities of a few cm2/(V s) at room temperature and even much higher values at low temperature, as shown in the pioneering work of Karl et al.7 However, for practical applications, thinfilm organic semiconductors with disordered morphology, such as evaporated small-molecule compounds or polymers processed from solution, are prevailing. Organic semiconductors are already broadly applied as photoconductors for copiers and laser printers. * Corresponding author. E-mail: leo@iapp.de. Web address: www.iapp.de. 1233 Chem. Rev. 2007, 107, 1233−1271

Highly efficient organic devices based on electrically doped transport layers.

The present invention provides a heterocyclic compound and an organic light-emitting device including the heterocyclic compound. The organic light-emitting devices using the heterocyclic compounds have high-efficiency, low driving voltage, high luminance and long lifespan.

Organic light-emitting device

One of the keys to highly efficient phosphorescent emission in organic light-emitting devices is to confine triplet excitons generated within the emitting layer. We employ “starburst” perfluorinated phenylenes (C60F42) as a both hole- and exciton-block layer, and a hole-transport material 4,4′,4″-tri(N-carbazolyl) triphenylamine as a host for the phosphorescent dopant dye in the emitting layer. A maximum external quantum efficiency reaches to 19.2%, and keeps over 15% even at high current densities of 10–20 mA/cm2, providing several times the brightness of fluorescent tubes for lighting. The onset voltage of the electroluminescence is as low as 2.4 V and the peak power efficiency is 70–72 lm/W, promising for low-power display devices.

Highly efficient phosphorescence from organic light-emitting devices with an exciton-block layer

Light aqueduct: Periodic mesoporous organosilica exhibits strong light absorption due to densely packed organic chromophores within the pore walls. Light energy absorbed by 125 biphenyl groups in the pore walls is funneled into a single coumarin 1 molecule in the mesochannels with almost 100 % quantum efficiency, and results in significant enhancement of emission from the coumarin 1 dye.

Light harvesting by a periodic mesoporous organosilica chromophore.

Hole-transporting framework is formed by surfactant-templated sol−gel polycondensation of an electroactive phenylenevinylene-based organosilane precursor. Molecular geometry of the three-armed precursor contributes to both formation of periodic mesostructures and introduction of hole conductivity in the organosilica hybrids. Electroactive organosilicas with mesopores and large surface areas have great potentials for novel photovoltaic and photocatalytic systems.

Hole-transporting periodic mesostructured organosilica.

An enhancement in the external quantum efficiency (QE) of red phosphorescent organic light-emitting devices (OLEDs) by using facially encumbered and bulky meso-aryl substituted Pt II porphyrin complexes is demonstrated. The maximum external QEs of phosphorescent OLEDs doped with the facially non-encumbered Pt II porphyrin complex 1 [5,15-bis[4-(4,4-dimethyl-2,6-dioxacyclohexyl)phenyl]-2,8,12,18-tetrahexyl-3,7,13,17-tetramethylporphyrin platinum(II)], the facially encumbered Pt II porphyrin complex 2 [5,15-bis(2,6-dimethoxyphenyl)-2,8,12,18-tetrahexyl-3,7,13,17-tetramethylporphyrinato platinum(II)], the Pt II porphyrin complex 3 that bears bulkier 3,5-di-tert-butylphenyl substituents [5,15-bis(3,5-di-t-butylphenyl)-2,8,12,18-tetrahexyl-3,7,13,17-tetramethylporphyrin platinum(II)], and the "doubly-decamethylene-strapped" Pt II porphyrin complex 4 were 1,4.2,7.3, and 8.2 %, respectively. The trend of increasing QE values in the order of 1<2<3<4 may be related to facial encumbrance and steric bulkiness ef meso-aryl substituted Pt II porphyrin complexes. Especially, in the case of the Pt II porphyrin 4, it is considered that the "double straps" play an important role in restricting rotational freedom of the meso-aryl substituents. The triplet excited-state lifetimes for Pt II porphyrins 1-4 in OLEDs at an injection current density of 0.55 mA cm -2 were 80, 103, 140, and 152 μs, respectively. We believe that the trend of increasing triplet lifetime in going from 1 to 4 is correlated with suppressing non-radiative decay.

Enhancement of External Quantum Efficiency of Red Phosphorescent Organic Light-Emitting Devices with Facially Encumbered and Bulky PtII Porphyrin Complexes

Synthesis of N,N,N′,N′-tetrasubstituted 1,3-bis(4-aminophenyl)azulenes and their application to a hole-injecting material in organic electroluminescent devices

Masamichi Ikai

Papers

Highly efficient phosphorescence from organic light-emitting devices with an exciton-block layer

Light harvesting by a periodic mesoporous organosilica chromophore.

Hole-transporting periodic mesostructured organosilica.

Enhancement of External Quantum Efficiency of Red Phosphorescent Organic Light-Emitting Devices with Facially Encumbered and Bulky PtII Porphyrin Complexes

Synthesis of N,N,N′,N′-tetrasubstituted 1,3-bis(4-aminophenyl)azulenes and their application to a hole-injecting material in organic electroluminescent devices