Horizontal Orientation of Disk-like Hole Transport Molecules and Their Application for Organic Light-Emitting Diodes Requiring a Lower Driving Voltage

2012 ◽  
Vol 116 (15) ◽  
pp. 8699-8706 ◽  
Author(s):  
Jun Y. Kim ◽  
Daisuke Yokoyama ◽  
Chihaya Adachi
Keyword(s):  
Light Emitting Diodes ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Driving Voltage ◽  
Light Emitting ◽  
Horizontal Orientation ◽  
Organic Light ◽  
Transport Molecules

scholarly journals Effects of the Thickness of N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine on the Electro-Optical Characteristics of Organic Light-Emitting Diodes

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 966
Author(s):  
Sang-Geon Park ◽  
Won Jae Lee ◽  
Min Jong Song ◽  
Johngeon Shin ◽  
Tae Wan Kim
Keyword(s):  
Current Efficiency ◽  
Current Density ◽  
Light Emitting Diodes ◽  
Light Emitting Diode ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Optical Characteristics ◽  
Driving Voltage ◽  
Light Emitting ◽  
Organic Light

We examined the electro-optical characteristics of organic light emitting diodes according to the N,N'-diphenyl-N,N'-di(m-tolyl)-benzidine (TPD) thicknesses. The thicknesses of TPD were varied from 5 nm to 50 nm. The current density of the device with a TPD thickness of 5 nm was 8.94 times higher than that with a thickness of 50 nm at a driving voltage of 10 V. According to the conduction–current characteristics of conductors, the current densities improved with a decreasing TPD thickness. Different from the current density–voltage characteristics, the current efficiency–current density characteristics showed an improved efficiency with a 50 nm TPD thickness. The current efficiencies of a device with a 5 nm TPD thickness at a driving voltage of 10 V was 0.148 and at a 50 nm TPD thickness 0.993 cd/A, which was 6.7 times higher than the 5 nm TPD thickness. These results indicated that hole transport in Organic Light-Emitting Diode (OLED) devices were more efficient with thin 5 nm TPD than with thick 50 nm TPD, while electron transport was more efficient with thick 50 nm TPD, which caused conflicting results in the current efficiency-current density and current density-voltage characteristics according to TPD thicknesses.

Substituted tetrapyrazolylporphyrins: application in organic light-emitting diodes

2005 ◽  
Vol 09 (12) ◽  
pp. 830-834 ◽  
Author(s):  
Can-Cheng Guo ◽  
Tie-Gang Ren ◽  
Jian-Xin Song ◽  
Qiang Liu ◽  
Kai Luo ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Driving Voltage ◽  
Free Base ◽  
Red Emission ◽  
Light Emitting ◽  
Host Layer ◽  
Organic Light ◽  
Electron Donating Groups

Six substituted tetrapyrazolylporphyrins ( TAPyPH 2), meso-tetrakis(1-phenylpyrazol-4-yl)porphyrin ( TPPyPH 2), meso-tetrakis[1-(p-tolyl)pyrazol-4-yl] porphyrin ((p- CH 3) TPPyPH 2), meso-tetrakis[1-(p-methoxyphenyl)pyrazol-4-yl]porphyrin ((p- CH 3 O ) TPPyPH 2), meso-tetrakis[1-(p-chlorophenyl) pyrazol-4-yl]porphyrin ((p- Cl ) TPPyPH 2), meso-tetrakis[1-(p-bromophenyl)pyrazol-4-yl]porphyrin ((p- Br ) TPPyPH 2) and meso-tetrakis[1-(m-tolyl)pyrazol-4-yl]porphyrin ((m- CH 3) TPPyPH 2), were synthesized by the condensation of pyrrole with the corresponding substituted formylpyrazole and used as the doping materials in the Organic Light-Emitting Diodes (OLEDs) with hole-transport materials of N , N '-diphenyl- N , N '-bis (4-methylphenyl)-[1,1'-biphenyl]-4,4'-diamine (TPD) within a tris(8-hydroxyquinoline) aluminum ( Alq 3) host layer. Both the electroluminescence properties of these OLEDs and effects of the peripheral substituents of the tetrapyrazolylporphyrins on EL properties of the OLEDs were studied. The tests found that the OLEDs using substituted tetrapyrazolylporphyrins ( TAPyPH 2) as the dopants had the saturated red emission at a concentration of 1.5 wt.%. The electron-donating groups of tetrapyrazolylporphyrins (for example, p- CH 3 and p- CH 3 O ) increased the luminance of OLEDs, while the electron-drawing groups (for example, p- Cl and p- Br ) decreased the luminance. The OLEDs using meso-tetrakis(1-phenylpyrazol-4-yl)porphyrin ( TPPyPH 2) as a dopant showed saturated red emission at 680 nm (CIE coordinates of x = 0.65, y = 0.31) with a luminance of 305 cd/m2 at a driving voltage of 25 V at concentration of 1.5 wt.%. Compared with OLEDs doped by the free-base tetraphenylporphyrin (TPPH2), the OLEDs doped by the tetrapyrazolylporphyrins had better luminance and higher emission efficiency. An explanation for these results was given based on the molecular structure and spectral properties of the porphyrin compounds.

Hole Transport Molecules in HighTgPolymers:  Their Effect on the Performance of Organic Light-Emitting Diodes

2001 ◽  
Vol 13 (5) ◽  
pp. 1739-1745 ◽  
Author(s):  
F. Santerre ◽  
I. Bedja ◽  
J. P. Dodelet ◽  
Y. Sun ◽  
J. Lu ◽  
...  
Keyword(s):  
Light Emitting Diodes ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Light Emitting ◽  
Organic Light ◽  
Transport Molecules

Improve the Charge Balance of White Phosphorescent Organic Light Emitting Diodes Using Co-Doped Electron Transport Layer in Emitting Layer

2011 ◽  
Vol 287-290 ◽  
pp. 3051-3055
Author(s):  
Yu Sheng Tsai ◽  
Lin Ann Hong ◽  
Fuh Shyang Juang ◽  
Kuang Chih Lai ◽  
Chang Jun Lai ◽  
...  
Keyword(s):  
Electron Transport ◽  
Power Efficiency ◽  
Light Emitting Diodes ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Electron Transport Layer ◽  
Driving Voltage ◽  
Light Emitting ◽  
Organic Light ◽  
Luminance Efficiency

White phosphorescent organic light-emitting diodes (WPHOLED) with high efficiency and low driving voltage were achieved by incorporating an electron transport material (3TPYMB) into a hole transport-type host (TCTA) as a mixed-host structure. For electrons, the emitting layer is nearly barrier-free until they reach the region of exciton formation, which keeps the driving voltage low. Therefore, improved the charge carrier balance within the emitting layer and enhanced the power efficiency of device. White PHOLED at a luminance of 1000 cd/m2 shown a driving voltage of 4.38 V, luminance efficiency of 36.1 cd/A, and power efficiency of 26.4 lm/W was observed. Furthermore, the power efficiency can be improved to 34.27 lm/W, and luminance efficiency to 46.7 cd/A by attaching a brightness enhancement film (BEF).

scholarly journals Solution-Processed Efficient Blue Phosphorescent Organic Light-Emitting Diodes (PHOLEDs) Enabled by Hole-Transport Material Incorporated Single Emission Layer

Materials ◽  
2021 ◽  
Vol 14 (3) ◽  
pp. 554
Author(s):  
Taeshik Earmme
Keyword(s):  
Light Emitting Diodes ◽  
Blue Emission ◽  
Hole Transport ◽  
Organic Light Emitting Diodes ◽  
Emission Layer ◽  
Solution Processed ◽  
Light Emitting ◽  
Organic Light ◽  
Single Emission ◽  
Blue Phosphorescent

Solution-processed blue phosphorescent organic light-emitting diodes (PHOLEDs) based on a single emission layer with small-molecule hole-transport materials (HTMs) are demonstrated. Various HTMs have been readily incorporated by solution-processing to enhance hole-transport properties of the polymer-based emission layer. Poly(N-vinylcarbazole) (PVK)-based blue emission layer with iridium(III) bis(4,6-(di-fluorophenyl)pyridinato-N,C2′)picolinate (FIrpic) triplet emitter blended with solution-processed 1,1-bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC) gave luminous efficiency of 21.1 cd/A at a brightness of 6220 cd/m2 with an external quantum efficiency (EQE) of 10.6%. Blue PHOLEDs with solution-incorporated HTMs turned out to be 50% more efficient compared to the reference device without HTMs. The high hole mobility, high triplet energy of HTM, and favorable energy transfer between HTM blended PVK host and FIrpic blue dopant were found to be important factors for achieving high device performance. The results are instructive to design and/or select proper hole-transport materials in solution-processed single emission layer.

Sign in / Sign up

Export Citation Format

Share Document