摘要:

AbstractA review of recent developments in the design and use of small molecular organic electroluminescent materials for display applications is presented. The material issues pertaining to transport properties, color, emission efficiencies, and operational stability are described.

ISSN:1022-1360    

DOI:10.1002/masy.19981250102

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractAt‐butyl substituted red fluorescent dye, 4‐(dicyanomethylene)‐2‐t‐butyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJTB), has been found to be an excellent dopant in AIQ3which produces a highly efficient organic EL device with improved red chromaticity. Unlike 4‐(dicyanomethylene)‐2‐methyl‐6‐(1,1,7,7‐tetramethyljulolidyl‐9‐enyl)‐4H‐pyran (DCJT), DCJTB can be synthesized in a pure form directly from theunsymmetrical4‐(dicyanomethylene)‐2‐(t‐butyl)‐6‐methyl‐4H‐pyran without the contamination of the non‐fluorescentbis‐condensation byproduct which is prevalent in the DCJT preparation. Both photoluminescence and electroluminescence in the solid films of DCJTB in AlQ3are modestly enhanced by the extra t‐butyl substitution as a result of a reduction in the effect of concentration quenching. The operation stability of the DCJTB doped EL device is superior, having a ha

ISSN:1022-1360    

DOI:10.1002/masy.19981250103

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractA study of the main failure mechanisms in vacuum vapor‐deposited organic light‐emitting diodes (LED's) is presented. Three degradation modes were identified for a prototype bilayer ITO/TPD/Alq3/Mg/Ag device: a) formation and growth of black non‐emissive spots, b) abrupt ceasing of light emission associated with catastrophic failures caused by electrical shorts, and c) long term wearout associated with the decrease of quantum efficiency and luminance along with an increase in voltage, while the device is stressed under constant cu

ISSN:1022-1360    

DOI:10.1002/masy.19981250104

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractWe have studied the photoluminescence properties of the metal chelates aluminum‐tris(8‐hydroxychinoline) (Alq3) and tris(4,4,4‐trifluoro‐1‐(2‐thienyl)‐1,3‐butanediono)‐1,10‐phenanthroline europium(III) (Eu(TTFA)3Phen) sandwiched between a planar Fabry‐Perot microcavity structure. A strong influence of the position of the emission thin film on the luminescence spectra has been observed. The emission intensity normal to the substrate surface is drastically enhanced by an order of a magnitude if the active layer is placed at the antinode of the standing wave in the cavity. In comparison to non‐resonant Alq3structures, the FWHM of the spectrum is reduced from 100 nm to about 20 nm. We also show that the Eu(TTFA)3Phen luminescence is spacially directed due to the inheren

ISSN:1022-1360    

DOI:10.1002/masy.19981250105

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractInfluence of emission sites on emission efficiency and running durability of molecular organic electroluminescent devices was investigated. When fluorescent dye rubrene was doped into TPD diamine hole transport layer, rubrene molecule emitted bright yellow light with a max. luminance of 61 000 cd/m2. The device had the highest efficiency of 9.8 Im/W at 100 cd/m2. Half‐decay time of the device from initial luminance of 530 cd/m2under constant direct current was 3 600 h. On the other hand, when rubrene was doped into BeBq2complex electron transport layer, the efficiency was 4.4 Im/W and the half‐decay time was 110 h. Thus doping site is found to exert significant influence both on the emission efficiency and the running durabil

ISSN:1022-1360    

DOI:10.1002/masy.19981250106

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractMetal/polymer interfaces play an important role in polymeric light emitting diodes (LEDs). In typical organic light‐emitting devices, metallic electrodes are used to inject charged carriers into the organic electroluminescent (EL) medium. However, what other effects the metals have on the organic medium is not well known. In this work, we report severe photoluminescence (PL) quenching of organic thin films comprising of one of the most useful materials, namely 1,4‐bis[4‐(3,5‐di‐tert‐butylstyryl)styryl]benzene (4PV), upon sub‐monolayer deposition of Al, Ag, and Ca in an ultra high vacuum environment. The severity of the luminescence quenching may greatly affect the EL device performance. Gap states at the Ca/4PV interface are shown to be responsible for the PL quenching. The oxidation of Ca resulted in the removal of the gap states and the recovery of th

ISSN:1022-1360    

DOI:10.1002/masy.19981250107

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractThis article presents an overview of the work that has been done recently in our laboratory concerning the development and application of new conjugated materials with tunable properties. We have designed polymers containing oligo(phenylenevinylene)‐type conjugated segments of well defined size and structure isolated either in their main‐chain or in the side‐chains. Model oligomers corresponding to the conjugated parts of the polymers have also been studied. We show how these materials perform in light‐emission applications (light‐emitting diodes, lasers) or photovolt

ISSN:1022-1360    

DOI:10.1002/masy.19981250108

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractStatistical copolymers5containing poly(2‐dimethyloctylsilyl‐1,4‐phenylenevinylene) (DMOS‐PPV) and poly[2‐methoxy‐5‐(2′‐ethylhexyloxy)‐1,4‐phenylenevinylene] (MEH‐PPV) have been synthesized using the dehydrohalogenation condensation route. The copolymers show a shift of photoluminescence maxima to longer wavelengths as the proportion of the MEH‐PV unit increases. This trend is accompanied by reduced efficiencies and lower turn‐on voltages in single layer electroluminescent devices. Light‐emitting electrochemical cells (LECs) have been prepared using a blend of DMOS‐PPV1with poly(ethylene oxide)/lithium triflate and the homopolymer poly[2‐methoxy‐5‐(triethoxymethoxy)‐1,4‐phenylene vinylene] (MTEM‐PPV)9with lithium triflate. In comparison with single‐layer devices which were fabricated using the homopolymers1and poly[2,5‐bis(triethoxymethoxy)‐1,4‐phenylene vinylene] (BTEM‐

ISSN:1022-1360    

DOI:10.1002/masy.19981250109

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractSpiro‐linkage of low molecular weight entities as a new structural concept for the design of new active materials for electroluminescent applications is presented. These spiro linked compounds result in nonpolymeric organic glasses with high thermal stability as can be derived from their high glass transition temperatures (Tg), and characterized by differential scanning calorimetry. Blue emitters based on spiro linked oligophenyles are presented. These compounds are soluble in common organic solvents and show high photoluminescence quantum efficiency in the solid state and high morphologic stability with glass transition temperatures up to 250°C. Charge transport materials based on spiro linked versions of 2‐(4‐biphenyl)‐5‐(4‐tert‐butylphenyl)‐1,3,4‐oxadiazole (PBD) for electron transport, and spiro linked versions of triphenyldiamin derivatives (TPD) for hole transport show improved morphologic properties with nearly unchanged electronic properties compared to the parent compounds.High quality amorphous films can be prepared with the spiro compounds by vapor deposition as well as by s

ISSN:1022-1360    

DOI:10.1002/masy.19981250110

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY

摘要:

AbstractAn alternating copolymer with monomer units of fluorene and phenylenedivinylene was synthesized by reaction between n‐hexyl fluorene phosphonium salt and isophthalic aldehyde based on the Wittig reaction. The polymer solution in chloroform was made into a film with a very fine surface by spin‐casting on indium‐tin oxide (ITO) coated glass to fabricate a light emitting diode (LED) with an aluminum negative electrode. The optical absorption spectrum of the solid film shows a peak at 370 ran while the PL spectrum has the main peak at 560 nm with a secondary peak at 440 nm and the EL spectrum has a single peak at 560 nm showing the Stokes shift of 190 nm. The peak in the PL spectrum shifts to 420 nm with a vibronic structure at 440 nm on either dilution by chloroform or blending with polyvinylcarbazole (PVK). The emissive polymer bulk seemed to generate sites for excimers and molecular aggregates which were diminished on the dilution or blending. The peak in the EL spectrum also shifts to 440 nm on blending of 20% of the copolymer with PVK. Further dilution to 10% of the copolymer shifts the EL peak to 420 nm with the onset potential of 15 V and the highest quantum efficiency of 0.01% in this series. The concentrated channels were developed in the blends with severe phase separation to show a lower onset potential but poor quantum effic

ISSN:1022-1360    

DOI:10.1002/masy.19981250111

出版商:Hüthig&Wepf Verlag    

年代:1998

数据来源: WILEY