• Macromolecular Research
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• v.13 no.5
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• pp.403-408
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• 2005

A new terphenylenevinylene carbazylenevinylene alternating copolymer with the advantage of poly(p-phenylenevinylene) (PPV), poly(p-phenylene )(PPP) and poly(carbazole) was designed, synthesized and characterized. The polymer structure was confirmed by various spectroscopic analyses and the number average molecular weight ($M_n$) of the obtained polymer was 7,800. The resulting polymer was thermally stable with high glass transition temperature ($T_g$) ($150^{\circ}C$), and was readily soluble in common organic solvents. Cyclic voltammetry study revealed that the HOMO and LUMO energy levels of the polymer were 5.37 and 2.47 eV, respectively. The ITO/PEDOT/polymer/AI device fabricated from the polymer emitted bright sky blue light with a maximum peak of around 478 nm. The device showed the maximum brightness of 1,200 nW with a turn-on voltage of 7V.

• JSTS:Journal of Semiconductor Technology and Science
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• v.4 no.2
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• pp.94-99
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• 2004

silicided 50-nm-gate-length n-type Schottky barrier metal-oxide-semiconductor field-effect-transistors (SB-MOSFETs) with 5 nm gate oxide thickness are manufactured. The saturation current is $120{\mu}A/{\mu}m$ and on/off-current ratio is higher than $10^5$ with low leakage current less than $10{\mu}A/{\mu}m$. Novel phenomena of this device are discussed. The increase of tunneling current with the increase of drain voltage is explained using drain induced Schottky barrier thickness thinning effect. The abnormal increase of drain current with the decrease of gate voltage is explained by hole carrier injection from drain into channel. The mechanism of threshold voltage increase in SB-MOSFETs is discussed. Based on the extracted model parameters, the performance of 10-nm-gate-length SB-MOSFETs is predicted. The results show that the subthreshold swing value can be lower than 60 mV/decade.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.06a
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• pp.159-159
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• 2008

Indium-tin oxides (ITO) films have been widely used as transparent electrodes for optoelectronic devices such as organic light emitting diodes (OLEDs), photovoltaics, touch screen devices, and flat-paneldisplay. In particular, to improve hole injection efficiency in OLEDs, transparent electrodes should have high work-function besides their transparency and low resistivity. Nevertheless, few studies have been made on engineering the work function of ITO for use as an efficient anode. In this study, the effects of a wide range of Nb or Zn doping rate on the changes in work functions of ITO anode were investigated. The Nb or Zn doped ITO films were fabricated on glass substrates using combinatorial sputtering system which yields a linear composition spread of Nb or Zn concentration in ITO films in a controlled manner by co-sputtering two targets of ITO and Nb2O5 or ITO and ZnO. We have also examined the resistivity, transmittance, and other structural properties of the Nb or Zn-doped ITO films. Furthermore, OLEDs employing Nb or Zn-doped ITO anodes were fabricated and the device performances were investigated concerned with the work function changes.

• 한국정보디스플레이학회:학술대회논문집
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• 2009.10a
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• pp.118-120
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• 2009

We reported that the evidence of oxygen doping to copper-phthalocyanine (CuPc) by $O_2$-plasma treatment to Au electrode of inverted top emitting organic light emitting diodes (ITOLEDs). The operation voltage of OLEDs at 150 mA/$cm^2$ decreased from 16.1 to 10.3 V as oxygen atoms indiffued to CuPc layer using $O_2$-plasma. Synchrotron radiation photoelectron spectroscopy results showed that a new bond of Cu-O appeared and the energy difference between the highest occupied molecular orbital and $E_F$ is lowered by 0.20 eV after plasma treatment. Thus the hole injection barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs.

• Journal of the Semiconductor & Display Technology
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• v.10 no.1
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• pp.27-32
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• 2011

In this study, we have investigated the power conversion efficiency of organic solar cells utilizing conjugated polymer/fullerene bulk-hetero junction(BHJ) device structures. We have fabricated poly(3-hexylthiophene)(P3HT), poly[2methoxy-5-(3',7'-dimethyloctyl-oxy)-1-4-phenylenevinylene] as an electron donor, [6,6]-phenyl $C_{61}$ butyric acid methylester(PCBM-$C_{61}$)as an electron acceptor, and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS) used as a hole injection layer(HIL), after fabricated active layer, between active layer and metal cathode(Al) deposited LiF interlayer(5 nm). The properties of fabricated organic solar cell(OSC) devices have been analyzed as a function of different thickness. The electrical characteristics of the fabricated devices were investigated by means J-V, fill factor(FF) and power conversion efficiency(PCE). We observed the highest PCEs of 0.628%(MDMO-PPV:PCBM-$C_{61}$) and 2.3%(P3HT:PCBM-$C_{61}$) with LiF inter-layer at the highest thick active layer, which is 1.3times better than the device without LiF inter-layer.

• Journal of the Semiconductor & Display Technology
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• v.18 no.3
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• pp.100-104
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• 2019

We have investigated the feasibility of fabricating fine stripes using needle coating for potential applications in solution-processed organic light-emitting diodes (OLEDs). To this end, we have employed an aqueous poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS) solution that has been widely used as a hole injection layer (HIL) of OLEDs and performed needle coatings by varying the process parameters such as the coating gap and coating speed. As expected, the stripe width is reduced with increasing coating speed. However, the central thickness of the stripe is rather increased as the coating speed increases, which is different from other coating processes such as slot-die and blade coatings. It is due to the fact that the meniscus formed between the needle tip and the substrate varies depending sensitively on the coating speed. It is also found that the stripe width and thickness are reduced with increasing coating gap. To demonstrate its applicability to OLEDs, we have fabricated a red OLED stripe and obtained light emission with the width of about 90㎛.

• KIEE International Transactions on Electrophysics and Applications
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• v.3C no.1
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• pp.19-22
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• 2003

The co-evaporated cathodes composed of A1 and CsF is adopted to enhance the electrical and the optical properties of organic light emitting diodes (OLEDs). The hole transport layer (HTL), made of 50nm thick N,N-dipheny1-N,N-bis(3-methylphenyl)-1,1-bipheny14,4-diamine (TPD), and the electron transport layer (ETL), made of 50nm thick tris(8-hydroxy-quinoline) aluminum (A1q$_3$), were deposited under the base pressure of 1.6$\times$10$^{-6}$ Torr. In depositing A1-CsF, the mass ratio of CsF is varied between 1 and 10wt%. OLEDs with co-evaporated cathodes have luminance of about 35,000cd/$m^2$, and external quantum efficiency of about 1.38%. Cs tends to diffuse into the organic layer and then re-forms Cs$^{+}$cation and free electron with the Cs-doped surface region.n.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.5
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• pp.409-417
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• 2003

We have studied electrical properties and luminous efficiency of organic light-emitting diodes(OLEDs) with different buffer layer and cathodes in a temperature range of 10 K and 300 K. Four different device structures were made. The OLEDs are based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as a hole transport, tris(8-hydroxyquinolinato) aluminum(III) (Alq$_3$) as an electron transport and omissive layer, and poly(3,4-ethylenedioxythiophene) :poly (styrenesulfonate) (PEDOT:PSS ) as a buffer layer. And LiAl was used as a cathode. Among the devices, the ITO/PEDOT:PSS/TPD/Alq$_3$/LiAl structure has a low energy-barrier height for charge injection and show a good luminous efficiency. We have got a highly efficient and low-voltage operating device using the conductive PEDOT:PSS and low work-function LiAl. From current-voltage characteristics with temperature variation, conduction mechanisms are explained SCLC (space charge limited current) and tunneling one. We have also studied energy barrier height and luminous efficiency at various temperature.

• Proceedings of the KIEE Conference
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• 2006.07c
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• pp.1293-1294
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• 2006

OLEDs based on organic thin films are similar to semiconductor base light-emitting diodes in that they were also considered to be one of the next generation flat-panel displays. They are attractive because of low-operating voltage, low power consumption, ease of fabrication, and low cost. In this study, we used poly (3,4-ethylenedioxythiophene)/poly (4-styrenesulfonate) (PE DOT : PSS) as a hole injection layer. In this experiment spin coating method was used with various speed rate. The fundamental structure of the OLEDs was ITO/PEDOT:PSS/NPB/$Alq_3$/Al. As a result, we obtained the enhancement performance of OLEDs when the spin coating speed was 4000 rpm. We obtained a maximum luminance of 24334 $cd/m^2$ at a current density of 967 $mA/cm^2$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.436-437
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• 2006

In this work, impedance Spectroscopic analysis was applied to study the effect of plasma treatment on the surface of indum-tin oxide (ITO) anodes using $O_2$ gas and to model the equivalent circuit for organic light emitting diodes (OLEDs) with the $O_2$ plasma treatment of ITO surface at the anodes. This device with ITO/TPD/Alq3/LiF/Al structure can be modeled as a simple combination of a resistor and a capacitor. The $O_2$ plasma treatment on the surface of ITO shifts the vacuum level of the ITO as a result of which the barrier height for hole injection at the ITO/organic interface is reduced. The impedance spectroscopy measurement of the devices with the $O_2$ plasma treatment on the surface of ITO anodes shows change of values in parallel resistance ($R_p$) and parallel capacitance ($C_p$).