• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.11a
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• pp.316-319
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• 2001

Organic light emitting diodes(OLEDs) with a hole injection layer inserted between Indium-Tin-Oxide(ITO) anode and hole transport layer were fabricated. The effect of plasma treatment on the surface properties of Indium-Tin-Oxide(ITO) anode were studied. The electrical and optical characteristics of the fabricated organic light emitting diodes(OLEDs) were also studied. The diode including of plasma treated ITO substrate and the hole injection layer, which showed the luminance of 5280 cd/㎡ at 8 V

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.31-32
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• 2008

The structure of OLEDs with conventional heterostructure consists of anode, hole injection layer, hole transport layer, light-emitting layer, electron transport layer, electron injection layer, and cathode. NPB used as a hole transport layer and 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 device's stability. Mixing of the hole transport layerand the emitting layer removes abrupt interface between the hole transport. layer and the electron transport layer. The stability of OLED with graded mixed-layer developed in this study was improved.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.69-70
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• 2006

We studied increasement of efficiency of Organic Light-emitting Diodes depending on thickness variation of LiF, Material of Electron Injection Layer in structure of ITO/Hole Injection Layer (PTFE)/Hole Transportion Later (TPD)/Emitting Layer (Alq3)/Electron Injection Layer (LiF)/Al. TPD and $Alq_3$ is deposited as rate of 1.3~1.5 [${\AA}/s$] in high vacuum ($5{\times}10^{-6}$ [torr]). In result of these studies, we can know maximum efficiency in 0.7 [nm], thickness of LiF. And samples with electron injection material are increased about 5-fold in maximum efficiency in compare with sample without electron injection material.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.310-310
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• 2009

In the two structure of ITO/N,N'-diphenyl-N,N' bis (3-methylphenyl)-1,1'-biphenyl-4,4'-diamine(TPD)/R-H : R-D/Al device, ITO/Amorphous Fluoropolymers/TPD/R-H : R-D/LiF/Al device. we studied the effect of organic materials defending on the electrical characteristics of red OLEDs. The thickness of TPD and R-H : R-D was manufactured 40 nm, 60 nm, respectively under a base pressure of $5\times10^{-6}$Torr using a thermal evaporation. The AF used for an hole-injection is the thickness of 0.5 [nm] and the LiF used for an electron-injection is the thickness of 0.5 [nm]. Compared to the two from the devices made with the hole injection and without hole injection We found that the luminous efficiency and the external quantum efficiency are improved a fact of one- hundred, two, respectively.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.14 no.8
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• pp.675-678
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• 2001

We fabricated the organic light emittign diodes (OLEDs) with ITO/Cu-Pc/triphenyl-diamine (TPD)/TPD+tris-(8-hydroxyquinoline) aluminum (Alq$_3$)/Al. The electrical properties of Cu-Pc thin film were studied as a hole injection layer. the energy gap of Cu-Pc thin films is decreased according to the substrate heat treatment temperature increased. It could be controlled the hole mobility by changing the heat treatment condition of Cu-Pc. The emission wavelengths could be controlled by changing hole mobility and recombination zone in emission layer.

• Transactions on Electrical and Electronic Materials
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• v.8 no.6
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• pp.260-264
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• 2007

We have studied stability in organic light-emitting diode depending on buffer layer and cathode. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. An electron injection energy barrier into organic material is different depending on a work function of cathodes. Theoretically, the energy barriers for the electron injection are 1.2 eV, -0.1 eV, and 0.0 eV for Al, LiAl, and LiF/Al at 300 K, respectively. We considered the cases that holes are injected to organic light-emitting diode. The hole injection energy barrier is about 0.7 eV between ITO and TPD without buffer layer. For hole-injection buffer layers of CuPc and PEDOT:PSS, the hole injection energy barriers are 0.4 eV and 0.5 eV, respectively. When the buffer layer of CuPc and PEDOT:PSS is existed, we observed the effects of hole injection energy barrier, and a reduction of operating-voltage. However, in case of PVK buffer layer, the hole injection energy barrier becomes high(1.0 eV). Even though the operating voltage becomes high, the efficiency is improved. A device structure for optimal lifetime condition is ITO/PEDOT:PSS/TPD/$Alq_3$/LiAl at an initial luminance of $300cd/m^2$.

• Transactions on Electrical and Electronic Materials
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• v.6 no.5
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• pp.233-237
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• 2005

In the device structure of ITO/hole injection layer/N, N'-biphenyl-N, N'-bis-(1-naphenyl)-[1,1'-biphenyl]4,4'-diamine(NPB)/tris(8-hydroxyquinoline) aluminum$(Alq_3)/Al$, we investigated an effect of hole-injection materials (PTFE, PVK) on the electrical characteristics and efficiency of organic light-emitting diodes. A thermal evaporation was performed to make a thickness of NPB layer with a evaporation rate of $0.5\~1.0\;\AA/s$ in a base pressure of $5\times10^{-6}$ Torr. We measured current-voltage characteristics and efficiency with a thickness variation of hole-injection layer. The PTFE and PVK hole-injection layer improve a performance of the device in several aspects, such as good mechanical junction, reducing the operating voltage and energy band adjustment. Compared with the devices without a hole-injection layer, we have obtained that an optimal thickness of NPB was 20 nm in the device structure of $ITO/NPB/Alq_3/Al$. And using the PTFE or PVK hole-injection layer, the external quantum efficiencies of the devices were improved by $24.5\%\;and\;51.3\%$, respectively.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.07b
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• pp.968-971
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• 2002

Hole injection characteristics have been investigated with various metal anodes such as Ni, Pt, Cu, and AI for the top emission polymer light emitting diodes (PLEDs). Devices were composed of metal anode, Poly(3,4-ethylenedioxythiophene) doped with polystyrene sultponated acid (PEDT:PSS), poly [2-methoxy-5-(2-ethylhexyoxy)-1,4-phenylene-vinylene] (MEH-PPV) and Al cathode. The hole injection from ITO anode has been also investigated for the comparison. The I-V characteristics of the PLEDs with different metal anodes were measured. The work function of the anode is strongly related to the hole injection of the device. The current density of the device with Ni anode with higher work function was higher than that of the device with ITO or AI anode at the same operating voltage.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.7
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• pp.622-626
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• 2003

We report the electrical properties of organic light emitting diodes (OLEDs) depending on the crystal structure of hole injection layer of copper(II)-phthalocyanine(CuPc) and the light irradiation the carrier mobility of copper(II)-phthalocyanine(CuPc) of light source. OLEDs were constructed with indium tin oxide(ITO)/CuPc/triphenyl-diamin(TPD)/tris-(8-hydroxyquinoline)aluminum(Alq$_3$)/Al.Photocurrent multiplication of OLEDs was varied by the heat-treatment condition of CuPc thin film and the light irradiation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.9
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• pp.771-774
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• 2003

In this paper, the programming characteristics of the multi-bit devices based on SONOS structure are investigated. Our devices have been fabricated by 0.35 $\mu\textrm{m}$ complementary metal-oxide-semiconductor (CMOS) process with LOCOS isolation. In order to achieve the multi-bit operation per cell, charges must be locally frapped in the nitride layer above the channel near the source-drain junction. Programming method is selected by Channel Hot Electron (CUE) injection which is available for localized trap in nitride film. To demonstrate CHE injection, substrate current (Isub) and one-shot programming curve are investigated. The multi-bit operation which stores two-bit per cell is investigated. Also, Hot Hole(HH) injection for fast erasing is used. The fabricated SONOS devices have ultra-thinner gate dielectrics and then have lower programming voltage, simpler process and better scalability compared to any other multi-bit storage Flash memory. Our programming characteristics are shown to be the most promising for the multi-bit flash memory.