• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.446-447
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• 2007

Aluminisum-doped zinc oxide (AZO) films are attractive materials as transparent conductive electrode because they are inexpensive, nontoxic and abundant element compared with indium tin oxide (ITO). In our paper, AZO films have been deposited on glass (coming 1737) substrates by RF magnetron sputtering. The AZO film was post-annealed at $600^{\circ}C$, $800^{\circ}C$ for 2 hr with $N_2$ atmosphere, respectively. We investigated that the electric properties and qualitative analysis of AZO films, which measured using the methods of Hall effect, X-ray photoelectron spectroscopy (XPS).

• Korean Journal of Materials Research
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• v.19 no.2
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• pp.108-110
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• 2009

Transparent Sn-doped $In_2O_3$ (ITO) single-layer and ITO/Au/ITO multilayer films were deposited on glass substrates by reactive magnetron sputtering to compare the properties of the films. They were then annealed in a vacuum of $1{\times}10^{-2}\;Pa$ at temperatures ranging from 150 to $450^{\circ}C$ for 20 min to determine the effect of the annealing temperature on the properties of the films. As-deposited 100 nm thick ITO films exhibit a sheet resistance of $130{\Omega}/{\square}$ and optical transmittance of 77% at a wavelength length of 550 nm. By inserting a 5 nm-thick Au layer in ITO/metal/ITO (IMI) films, the sheet resistance was decreased to as low as $20{\Omega}/{\square}$ and the optical transmittance was decreased to as little as 73% at 550 nm. Post-deposition annealing of ITO/Au/ITO films led to considerably lower electrical resistivity and higher optical transparency. In the Xray diffraction pattern, as-deposited ITO films did not show any diffraction peak, whereas as-deposited ITO/ Au/ITO films have Au (222) and $In_2O_3$ (110) crystal planes. When the annealing temperature reached the 150 - $450^{\circ}C$ range, the both diffraction peak intensities increased significantly. A sheet resistance of $8{\Omega}/{\square}$ and an optical transmittance of 82% were obtained from the ITO/Au/ITO films annealed at $450^{\circ}C$.

• Polymer(Korea)
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• v.32 no.4
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• pp.372-376
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• 2008

Vacuum deposited 4,4',4"-tris(N-(2-naphthyl)-N-phenylamino)-triphenylamine (2-TNATA), used as a hole injection (HIL) material in OLEDs, is placed as a thin interlayer between indium tin oxide (ITO) electrode and a hole transporting layer (HTL) in the devices. C60-doped 2-TNATA:C60 (20 wt%) film was formed via co-evaporation process and molecular ordering and topology of 2-TNATA:C60 films were investigated using XRD and AFM. The J-V, L-V and current efficiency of multi-layered devices were characterized as well. Vacuum-deposited C60 film was molecularly oriented, but neither was 2-TNATA:C60 film due to the uniform dispersion of C60 molecules in the film. By using C60-doped 2-TNATA:C60 film as a HIL, the current density and luminance of a multi-layered ITO/2-TNATA:C60/NPD/$Alq_3$/LiF/Al device were significantly increased and the current efficiency of the device was increased from 4.7 to 6.7 cd/A in the present study.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.2
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• pp.23-28
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• 2008

To improve the external quantum efficiency by means of the optimization of the polymer light emitting diodes(PLEDs) structure, the PLED with ITO/PEDOT:PSS/(PFO)/PFO:MEH-PPV/LiF/Al structure were fabricated and investigated the electrical and optical properties for the prepared devices. ITO(indium tin oxide) and PEDOT:PSS [poly (3,4-ethylenedioxythiophene): poly(styrene sulfolnate)] were used as transparent anode film and hole transport materials, respectively. PFO[poly(9,9-dioctylfluorene)] and MEHPPV[poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and dopant materials. The doping concentration of MEH-PPV was 9wt% with thickness of about $400{\AA}$. We investigated the dependence of the PFO thickness ranging from $200{\AA}$ to $300{\AA}$ on the electrical, optical properties of PLEDs. Among prepared PLED devices with different PFO thicknesses, the highest value of the luminance was obtained for the PLED device with $250{\AA}$ in thickness. As a result, the current density and luminance ware found to be about $400mA/cm^2$ and $1500cd/m^2$ at 13V, respectively. In addition, the luminance and current efficiency of PLED device with double emitting layer (PFO/PFO:MEH-PPV) were improved about 3 times compared with the one with single emitting layer (PFO:MEH-PPV).

• Applied Chemistry for Engineering
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• v.26 no.6
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• pp.640-647
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• 2015

As the need for next-generation flexible electronics grows, novel materials and technologies that can replace conventional indium tin oxide (ITO) for transparent electrodes have been of great interest. Among them, a conducting polymer, especially poly(3,4-ethylenedioxythiophene) : poly(styrene sulfonate) (PEDOT : PSS) is one of the most promising candidates because it is mechanically flexible, inexpensive, and capable of being processed in solution. Currently, there are a lot of research efforts on enhancing its electrical conductivity to the level of ITO or metal electrodes through chemical and/or physical processing. In this review article, we present various additives and pre-/post-deposition processing methods for improving the electrical conductivity of PEDOT : PSS. Some of representative reports are also introduced, which demonstrated the use of conductivity-enhanced PEDOT : PSS as transparent electrodes in electronics and energy conversion.

• Journal of the Microelectronics and Packaging Society
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• v.15 no.4
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• pp.59-64
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• 2008

In this paper, white polymer light emitting diodes(WPLEDs) were fabricated and investigated the electrical and optical properties for the prepared devices. ITO(indium tin oxide) and PEDOT:PSS [poly(3,4-ethylenedioxythiophene):poly(styrene sulfolnate)] as anode and hole injection materials, PFO [poly(9,9-dioctylfluorene)] and MEH-PPV [poly(2-methoxy-5(2-ethylhe xoxy)-1,4-phenylenevinyle)] were used as the light emitting host and guest materials, respectively. The LiF(lithium flouride) and Al(aluminum) were used electron injection materials and cathode materials. Finally, the WPLED with structure of ITO/PEDOT:PSS/PFO:MEH-PPV/LiF/Al was fabricated. The prepared WPLED showed white emission with CIE coordinates of (x=0.36, y=0.35) at the applied voltage of 9V. The maximum current density and luminance were about $740mA/cm^2\;and\;900cd/m^2$ at 13V, respectively. And the maximum current efficiency was 0.37 cd/A at $200cd/m^2$ in luminance.

• Journal of the Korean institute of surface engineering
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• v.42 no.1
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• pp.21-25
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• 2009

Using an evaporation system, $SiO_2$ was deposited as a buffer layer between a PET substrate and a ITO layer and then ITO/$SiO_2$/PET layers were annealed for 1.5 hours at the temperature of $180^{\circ}C$. Adhesion and electro-optical properties of ITO films were studied with thickness variance of a $SiO_2$ buffer layer. As a result of introduction of the $SiO_2$ buffer layer, sheet resistance and resistivity increased and a ITO film with optimum sheet resistance ($529.3{\Omega}/square$) for an upper ITO film of resistive type touch panel could be obtained when $SiO_2$ of $50{\AA}$ was deposited. And it was found that ITO films with $SiO_2$ buffer layer have higher transmittance of $88{\sim}90%$ at 550 nm wavelength than ITO films with no buffer layers and the transmittance was enhanced as $SiO_2$ thickness increased from $50{\AA}$ to $100{\AA}$. Adhesion property of ITO films with $SiO_2$ buffer layers became better than ITO films with no buffer layers and this property was independent of $SiO_2$ thickness variance ($50{\sim}100{\AA}$). By depositing a $SiO_2$ buffer layer of $50{\AA}$ on the PET substrate and sputtering a ITO thin film on the layer, a ITO film with enhanced adhesion, electro-optical properties could be obtained.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.347.2-347.2
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• 2016

Recently, in order to improve the performance of the colloidal quantum dot solar cells (CQDSCs), various efforts such as the modification of the cell architecture and surface treatment for quantum dot (QD) passivation have been made. Especially, the incorporation of halides into the QD matrix was reported to improve the performances significantly via passivating QD trap states that lower the life-time of the minority-carrier. In this work, we fabricated a lead sulfide (PbS) QD bilayer treated with different ligands and utilized it as a photoactive layer of the CQDSCs. The bottom and top PbS layer was treated using metal iodide ($MI_x$ and butanedithiol (BuDT), respectively. All the depositions and ligand treatments were carried out in air using layer-by-layer spin-coating process. The fabrication of the active layers as well as the n-type zinc oxide (ZnO) layer was successfully carried out on the bendable indium-tin-oxide (ITO)-coated polyethylene terephthalate (PET) substrate, which implies that this technique can be applied to the fabrication of flexible and/or wearable solar cells. The power conversion efficiency (PCE) of the CQDSCs with the architecture of $PET/ITO/ZnO/PbS-MI_x/PbS-BuDT/MoO_x/Ag$ reached 4.2 %, which is significantly larger than that of the cells with single QD (PbS-BuDT) layer.

• Proceedings of the Korean Vacuum Society Conference
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• 2015.08a
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• pp.143.2-143.2
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• 2015

백색유기발광소자는 저전력, 높은 명암비 및 빠른 응답속도와 넓은 시야각 등의 장점을 가지고 있어 대형 디스플레이, 모바일 디스플레이, 백색 광원 등에 사용되는 차세대 광원으로써 각광 받고 있고 이를 상용화하기 위해 많은 연구가 진행되고 있다. 하지만 다층 발광층을 가지는 백색유기발광소자는 발광층에 지역이 인가된 전압에 의해 바뀌어 색안정성이 떨어진다는 단점을 가지고 있다. 본 연구에서는 백색유기발광소자의 발광 메커니즘 규명하고 색안정성을 고찰하였다. 이 백색유기발광 소자는 indium-tin-oxide (ITO) 양극전극에 진공 증착 방법을 통해 전하생성층으로 tungsten oxide(WO3)층과 5,6,11,12-tetraphenyltetracene(rubrene)가 도핑된 N,N',-bis-(1-naphthyl)-N,N'-diphenyl1-1'-biphenyl-4,4'-diamine(NPB)층을 사용하여 제작되었다. ITO를 양극으로, NPB를 정공수송층으로, DPVBi를 발광층으로, 4,7-diphenyl-1,10-phenanthroline(BPhen)을 전자수송층으로, WO3와 0, 1, 2, 또는 3 wt% rubrene 도핑된 NPB를 전하생성층으로, Liq를 전자주입지연층으로, Al을 음극 전극으로 각각 사용하였다. 전하생성층으로 사용한 NPB층의 rubrene 도핑농도가 변화하여 백색유기발광소자의 발광 메커니즘을 규명하였다. rubrene 도핑된 NPB층에서 발광하는 노란빛과 발광층에서 발생하는 파란빛에 의해 백색광을 방출, NPB층에 도핑된 rubrene 도핑 농도가 증가할수록 소자의 전류밀도와 밝기가 증가했다.

• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.336.2-336.2
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• 2014

Indium Tin Oxide (ITO) thin films are used as the Transparent Conducting Oxide (TCO), such as flat panel display, transparent electrodes, solar cell, touch screen, and various optical devices. ZnO has attracted attention as alternative materials to ITO film due to its resource availability, low cost, and good transmittance at the visible region. Recently, very thin film deposition is important. In order to minimize the damage caused by bending. However, ZnO thin film such as Ga-doped ZnO(GZO) has poor sheet resistance characteristics. To solve this problem, By adding the conductive metal on films can decrease the sheet resistance and increase the mobility of the films. In this study, We analyzed the electrical and optical characteristics of GZO/Ag/GZO (GAG) films by change in Ag and GZO thickness.