• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2004년도 Asia Display / IMID 04
• /
• pp.612-615
• /
• 2004

We present an extremely high efficient red organic light-emitting diodes (OLEDs) using a fluorescent dye 4-(dicyanomethylene)-2-tert-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB) doped into an emitting region which consists of multiple pairs of a doped and an undoped layer. An emitting region of OLEDs composes of a tris-(8-hydroxyquinolinato) aluminum (Alq3) codoped with rubrene of 5% wt. or a mixture of Alq3 and rubrene (1:1). The luminance yield of the codoped device and the mixed device are 6.5 cd/A and 9.2 cd/A at 10 mA/$cm^2$, respectively. We have considerably improved the luminance yields of red OLEDs as much as ${\sim}$90% at 10 mA/$cm^2$ compared with that of the device doped with only DCJTB. We attribute it to both the emitting assist dopant (rubrene) and the dotted-line doping structure in an emitting region of OLED.

• 한국세라믹학회지
• /
• 제44권6호
• /
• pp.303-307
• /
• 2007

Transparent In-doped zinc oxide (IZO) thin films are deposited with variation of pulsed DC power at Ar atmosphere on coming 7059 glass substrate by pulsed DC magnetron sputtering. A c-axis oriented IZO thin films were grown in perpendicular to the substrate. The optical transmittance spectra showed high transmittance of over 80% in the UV-visible region and exhibited the absorption edge of about 350 nm. Also, the IZO films exhibited the resistivity of ${\sim}10^{-3}{\Omega}\;cm$ and the mobility of ${\sim}6cm/V\;s$. Organic Light-emitting diodes (OLEDs) with IZO/N,N'-diphenyl-N, N'-bis(3-methylphenl)-1, 1'-biphenyl-4,4'-diamine (TPD)/tris (8-hydroxyquinoline) aluminum ($Alq_3$)/LiF/Al configuration were fabricated. LiF layer inserted is used as an interfacial layer to increase the electron injection. Under a current density of $100\;mA/cm^2$, the OLEDs show an excellent efficiency (9.4 V turn-on voltage) and a good brightness ($12000\;cd/m^2$) of the emission light from the devices. These results indicate that IZO films hold promise for anode electrodes in the OLEDs application.

• 한국전기전자재료학회논문지
• /
• 제21권9호
• /
• pp.853-858
• /
• 2008

The structure of organic light-emitting diodes(OLEDs) with typical heterostructure consists of anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. 4,4bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl(NPB) used as a hole transport layer and 4'4-bis(2,2'-diphenyl vinyl)-1,1'-biphenyl(DPVBi) used as a blue light emitting layer were graded-mixed at selected ratio. Interface at heterojunction between the hole transport layer and the elecrtron transport layer restricts carrier's transfer. Mixing of the hole transport layer and the emitting layer reduces abrupt interface between the hole transport layer and the electron transport layer. The operating voltage of OLED devices with graded mixed-layer structure is 2.8 V at 1 $cd/m^2$ which is significantly lower than that of OLED device with typical heterostructure. The luminance of OLED devices with graded mixed-layer structure is 21,000 $cd/m^2$ , which is much higher than that of OLED device with typical heterostructure. This indicates that the graded mixed-layer enhances the movement of carriers by reducing the discontinuity of highest occupied molecular orbital(HOMO) of the interface between hole transport layer and emitting layer.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2006년도 6th International Meeting on Information Display
• /
• pp.1075-1078
• /
• 2006

New iridium complex was synthesized and demonstrated a deep red light emission in organic light-emitting diodes (OLEDs). The maximum luminance of 8320 cd/m2 at 15 V and the luminance efficiency of 2.5 cd/A at 20 mA/cm2 were achieved. The peak wavelength of the electroluminescence was at 626 nm with the CIE coordinates of (0.69, 0.30), and the device also showed a stable color chromaticity with various voltages.

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2009년도 9th International Meeting on Information Display
• /
• pp.415-417
• /
• 2009

Color stable and efficient two wavelength white organic light emitting diodes (OLEDs) were fabricated using a iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,$C^2$'] picolinate (FIrpic) as a blue phosphorescent emitter and a bis(1-phenylisoquinolinato-$C^2$,N)iridium (acetylacetonate) ((piq)$_2$Ir(acac)) as a red phosphorescent emitter. The emitting layers consist of two blue emitting layers and one red emitting layer which is between the two blue layers. The device reaches the peak efficiencies of 7.84 % and 10.3 cd/A at 0.6 mA/$cm^2$. Furthermore, there was little change of EL spectra according to current density change in the device.

• Bulletin of the Korean Chemical Society
• /
• 제34권5호
• /
• pp.1355-1360
• /
• 2013

We have developed a new multifunctional material, 4,4',4"-tris(4-naphthalen-2-yl-phenyl)amine (2-TNPA), which can be used as a blue-emitting and hole-transporting material in organic light-emitting diodes (OLEDs), as well as a donor material in organic solar cells (OSCs) and an active material in organic thin-film transistors (OTFTs). The OLED device doped with 3% 2-TNPA shows a maximum current efficiency of 3.0 $cdA^{-1}$ and an external quantum efficiency of 3.0%. 2-TNPA is a more efficient hole-transporting material than 4,4'-bis[N-(naphthyl-N-phenylamino)]biphenyl (NPD). Furthermore, 2-TNPA shows a power-conversion efficiency of 0.39% in OSC and a field-effect mobility of $3.2{\times}10^{-4}cm^2V^{-1}s^{-1}$ in OTFTs.

• 한국전기전자재료학회논문지
• /
• 제28권5호
• /
• pp.344-349
• /
• 2015

A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/$Alq_3$/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/$Alq_3$/BCP/Lif/Al were studied experimentally.

• Bulletin of the Korean Chemical Society
• /
• 제35권6호
• /
• pp.1670-1674
• /
• 2014

Two red emitters, 2-(7-(4-(diphenylamino)styryl)-2-methyl-4H-chromen-4-ylidene)malonitrile (Red 1) and 2-(7-(julolidylvinyl)-2-methyl-4H-chromen-4-ylidene)malonitrile (Red 2) have been designed and synthesized for application as red-light emitters in organic light emitting diodes (OLEDs). In these red emitters, the julolidine and triphenyl moieties were introduced to the emitting core as electron donors, and the chrome-derived electron accepting groups such as 2-methyl-(4H-chromen-4-ylidene)malononitrile were connected to electron donating moieties by vinyl groups. To explore the electroluminescence properties of these materials, multilayered OLEDs using red materials (Red 1 and Red 2) as dopants in $Alq_3$ host were fabricated. In particular, a device using Red 1 as the dopant material showed maximum luminous efficiencies and power efficiencies of 0.82 cd/A and 0.33 lm/W at $20mA/cm^2$. Also, a device using Red 2 as a dopant material presented the CIEx,y coordinates of (0.67, 0.32) at 7.0 V.

• Bulletin of the Korean Chemical Society
• /
• 제29권11호
• /
• pp.2270-2272
• /
• 2008

• 한국정보디스플레이학회:학술대회논문집
• /
• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
• /
• pp.66-69
• /
• 2007

We have investigated printing techniques for processing organic light-emitting diodes (OLEDs). We succeeded to gravure print uniform organic thin films as well as screen print low work function cathode for OLED structure. Furthermore, by using roll-to-roll manufacturing methods, we have been able to fabricate all-printed flexible OLED demonstrator.