Improvement of luminescence efficiency by electrical annealing in single-layer organic light-emitting diodes based on a conjugated dendrimer

In this paper, we study the effects of electrical annealing at different voltages on the performance of organic light-emitting diodes. The light-emitting diodes studied here are single-layer devices based on a conjugated dendrimer doped with 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the emissive layer. We find that these devices can be annealed electrically by applying a voltage. This process reduces the turn-on voltage and enhances the brightness and efficiency. We obtained an external electroluminescence quantum efficiency of 0.07% photon/electron and a brightness of 2900 cd m(-2) after 12.4 V electrical annealing, which are about 6 times and 9 times higher than un-annealing devices, respectively. The improved luminance and efficiency are attributed to the presence of a space charge field near the electrodes caused by charging of traps.

[1]  I. Samuel,et al.  Control of electrophosphorescence in conjugated dendrimer light-emitting diodes , 2001 .

[2]  H. Bässler,et al.  Control of mobility in molecular organic semiconductors by dendrimer generation , 2001 .

[3]  O. Park,et al.  Effect of electrical annealing on the luminous efficiency of thermally annealed polymer light-emitting diodes , 2000 .

[4]  Liping Ma,et al.  Device performance and polymer morphology in polymer light emitting diodes: The control of device electrical properties and metal/polymer contact , 2000 .

[5]  Yijian Shi,et al.  Device performance and polymer morphology in polymer light emitting diodes: The control of thin film morphology and device quantum efficiency , 2000 .

[6]  E. W. Meijer,et al.  Energy transfer in supramolecular assemblies of oligo(p-phenylene vinylene)s terminated poly(propylene imine) dendrimers , 2000 .

[7]  Mark E. Thompson,et al.  Improving the performance of conjugated polymer-based devices by control of interchain interactions and polymer film morphology , 2000 .

[8]  I. Samuel,et al.  Electroluminescence from a new distyrylbenzene based triazine dendrimer , 2000 .

[9]  Yoshio Taniguchi,et al.  Charge carrier trapping effect by luminescent dopant molecules in single-layer organic light emitting diodes , 1999 .

[10]  F. Huang,et al.  Role of ionic species in determining characteristics of polymer LEDs , 1999 .

[11]  Ching Wan Tang,et al.  Interface engineering in preparation of organic surface-emitting diodes , 1999 .

[12]  S. Mukamel,et al.  Exciton-scaling and optical excitations of self-similar phenylacetylene dendrimers , 1999 .

[13]  I. Samuel,et al.  CONJUGATED DENDRIMERS FOR LIGHT-EMITTING DIODES : EFFECT OF GENERATION , 1999 .

[14]  M. Rubner,et al.  SOLID-STATE LIGHT-EMITTING DEVICES BASED ON THE TRISCHELATED RUTHENIUM(II)COMPLEX. 1. THIN FILM BLENDS WITH POLY(ETHYLENE OXIDE) , 1998 .

[15]  F. E. Karasz,et al.  Bright red electroluminescence from a dye/copolymer blend , 1998 .

[16]  H. Sasabe,et al.  HYPERBRANCHED POLYMERS FOR ELECTROLUMINESCENCE APPLICATIONS , 1998 .

[17]  Alan G. MacDiarmid,et al.  AN IODINE-DOPED POLYMER LIGHT-EMITTING DIODE , 1997 .

[18]  J. C. Scott,et al.  Enhanced luminance in polymer composite light emitting devices , 1997 .

[19]  H. Bässler,et al.  Charge carrier recombination in organic bilayer electroluminescent diodes. I. Theory , 1997 .

[20]  H. Aziz,et al.  ELECTRIC-FIELD-INDUCED DEGRADATION OF POLY(P-PHENYLENEVINYLENE) ELECTROLUMINESCENT DEVICES , 1997 .

[21]  Yang Yang,et al.  Efficient blue-green and white light-emitting electrochemical cells based on poly[9,9-bis(3,6-dioxaheptyl)-fluorene-2,7-diyl] , 1997 .

[22]  Michael R. Shortreed,et al.  Spectroscopic Evidence for Excitonic Localization in Fractal Antenna Supermolecules , 1997 .

[23]  Ching Wan Tang,et al.  Organic electroluminescent devices with improved stability , 1996 .

[24]  J. J. M. Vleggaar,et al.  Electron and hole transport in poly(p‐phenylene vinylene) devices , 1996 .

[25]  Jeffrey S. Moore,et al.  Electroluminescent diodes from a single component emitting layer of dendritic macromolecules , 1996 .

[26]  Michel Schaer,et al.  Effects of doping in polymer light‐emitting diodes , 1995 .

[27]  R. H. Friend,et al.  Efficient light-emitting diodes based on polymers with high electron affinities , 1993, Nature.

[28]  A. Miura,et al.  Molecular design for nonpolymeric organic dye glasses with thermal stability : relations between thermodynamic parameters and amorphous properties , 1993 .

[29]  A. Heeger,et al.  Improved efficiency in semiconducting polymer light-emitting diodes , 1991 .

[30]  R. N. Marks,et al.  Light-emitting diodes based on conjugated polymers , 1990, Nature.

[31]  C. Tang,et al.  Organic Electroluminescent Diodes , 1987 .