• Proceedings of the Korean Vacuum Society Conference
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• 2014.02a
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• pp.391.2-391.2
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• 2014

Solution-processible hybrid bipolar field effect transistors (HBFETs) with balanced hole and electron mobilities were fabricated using a combination of the organic p-type poly (3-hexylthiophene) (P3HT) layer and inorganic n-type ZnO material. The hole and electron mobilities were first optimized in single layer devices by using acetonitrile as a solvent additive to process the P3HT and annealing to process the ZnO layer. The highest hole mobility of the P3HT-only-devices with 5% acetonitrile was 0.15 cm2V-1s-1, while the largest electron mobility was observed in the ZnO-only-devices annealed at $200^{\circ}C$ and found to be $7.2{\times}10-2cm2V-1s-1$. The inorganic-organic HBFETs consisting of P3HT with 5% acetonitrile and ZnO layer annealed at $200^{\circ}C$ exhibited balanced hole and electron mobilities of $4.0{\times}10-2$ and $3.9{\times}10-2cm2V-1s-1$, respectively. The effect on surface morphology and crystallinity by adding acetonitrile and thermal annealing were investigated through X-ray diffraction and atomic force microscopy (AFM). Our findings indicate that techniques demonstrated herein are of great utility in improving the performance of inorganic-organic hybrid devices

• Journal of the Korean Graphic Arts Communication Society
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• v.22 no.2
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• pp.179-198
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• 2004

Organic electroluminescent devices are light-emitting diodes in which the active materials consist entirely of organic materials. Recently, many fluorescent organic materials have been reported and the study on synthesis and application of new organic light-emitting materials has been demanded. This paper reports the optical and electrical characteristics of OLEDs using novel polymers containing biphenyl structure. First, Optical properties of novel light-emitting biphenyl derivatives doped with poly(9-vinyl carbazole)(PVK) and emitted blue, bluish green color, which is attributed to the overlap area between PL spectrum of host(PVK) and absorption spectra of guests(polymer). This is correspondent with F$\"{o}$rster energy transfer process in the blends. And, OLED devices were fabricated using poly (3,4-ethylenedioxy thiophene) (PEDOT) as a hole injection material and tris-(8-hydroxyquinoline) aluminum ($Alq_3$) as an electron transporting material. EL devices fabricated as ITO/PEDOT/PVK doped with biphenyl derivatives/$Alq_3$/Li:Al and I-V-L chatacteristics and emitting efficiency of EL devices were examined. Finally, the drift mobility of PVK doped with biphenyl derivatives and $Alq_3$ were measured by TOF technique varying applied electric field. EL efficiency was increased as the ratio of hole mobility of PVK doped with biphenyl derivatives and electron mobility of $Alq_3$ was close to one.

• Korean Journal of Digital Imaging in Medicine
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• v.8 no.1
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• pp.51-55
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• 2006

The effects of Asaddition in amorphous selenium(a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating(MPG) technique. This method utilizes the moving interference pattern generated by the superposition of the two frequency shifted laser beams for the illumination of the sample. This moving intensity grating induces a short circuit current, j$_{sc}$ in a-Se:As film. The transport parameters of the sample are extracted from the grating-velocity dependent short circuit current induced in the sample along the modulation direction. The electron and hole mobility, and recombination lifetime of a-Se films with arsenic(As) additions have been obtained. We have found an Increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As device. The fabricated a-Se(0.3% As) device film exhibited the highest X-ray sensitivity out of 5 samples.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.1047-1052
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• 2003

Controlling carrier transport in light emitting polymers is extremely important for their efficient use in organic opto-electronic devices [1]. Here we show that the interactions between single wall carbon nanotubes (SWNTs) and conjugated polymers can be used to modify the overall mobility of charge carriers within nanotube-polymer nanocomposites. By using a unique, double emitting-organic light emitting diodes (DE-OLEDs) structure. we have characterized the hole transport within electroluminescent nanocomposites (nanotubes in poly (m-phenylene vinylene-co-2,5-dioctoxy-p-phenylene) or PmPV). We have shown using this idea that single devices with color tunability can be fabricated. It is seen that SWNTs in PmPV are responsible for hole trapping, leading to shifts in the emission wavelengths. Our results could lead to improved organic optical amplifiers, semiconducting devices, and displays.

• Proceedings of the Materials Research Society of Korea Conference
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• 2010.05a
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• pp.56.1-56.1
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• 2010

A novel electrochemical potentiostatic method has been examined in order to enhance the hole concentration of p-type GaN thin films using KOH and HCl electrolyte. The hole concentration was increased more than 2 times by the electric voltge apply with the mobility of $10{\sim}12cm^2/V.s$. At optimum condition of 3V apply, hole concentration was enhanced more than reference sample from $1.7{\times}10^{-17}cm^{-3}$ to $4.1{\times}10^{-17}cm^{-3}$. Application of this activation method to blue-LED fabrication improved optical output from 18.4mW to 20.6mW, that is ~12% increase. SIMS analysis indicates that nearly 70% of hydrogen atoms could be removed by this method.

• 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.

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.280.2-280.2
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• 2016

The graphene, a single atomic sheet of graphite, has attracted tremendous interest owing to its novel properties including high intrinsic mobility, optical transparency and flexibility. However, for more diverse application of graphene devices, it is essential to tune its transport behavior by shifting Dirac Point (DP) of graphene. So, in the following context, we suggest a method to tune structural and electronic properties of graphene using atomic layer deposition. By atomic layer deposition of zinc oxide (ZnO) on graphene using 4-mercaptophenol as linker, we can fabricate n-doped graphene. Through ${\pi}-{\pi}$ stacking between chemically inert graphene and 4-mercaptophenol, conformal deposition of ZnO on graphene was enabled. The electron mobility of graphene TFT increased more than 3 times without considerably decreasing the hole mobility, compared to the pristine graphene. Also, it has high air stability. This ZnO doping method by atomic layer deposition can be applicable to large scale array of CVD graphene TFT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2001.07a
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• pp.947-950
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• 2001

We report the characteristics of organic light emitting diodes (OLEDS) by controlling the carrier mobility according to the crystalline of Iron(II) Phthalocyanine(Fe-Pc) and metal-free Phthalocyanine (H$_2$-Pc). In order to change the recombination zone, we controlled the hole mobility by changing the crystal structures of Fe-Pc and H$_2$-Pc. OLEDs were constructed with ITO/Fe-Pc/triphenyl-diamine (TPD)/tris-(8-hydroxyquinoline)aluminum (Alq$_3$)/Al and ITO/H$_2$-Pc/triphenyl-diamine (TPD)/tris-(8-hydroxyquinoline)aluminum (Alq$_3$)/Al. The electroluminescent properties were changed according to the heat-treatments of Fe-Pc and H$_2$-Pc. We observed that the recombination zone and the carrier mobility were changed as the higher occupied molecular orbital levels of Fe-Pc and H$_2$-Pc decreased.

• Macromolecular Research
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• v.14 no.6
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• pp.630-633
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• 2006

In heterojunction photovoltaic devices of $ITO/TiO_2/poly$(3-alkylthiophene)/Au, the photo current was characterized at different temperatures for different alkyl chain lengths and regioregularities: regiorandom, regioregular poly(3-hexylthiophene), and regioregular poly(3-dodecylthiophene). The regioregularity and alkyl chain length affected the photovoltaic characteristics due to differences in hole-carrier transportation. The drift charge mobilities of these devices were analyzed by the space-charge-limited current theory using the relation between the dark current and the bias voltage. The photocurrent in the devices based on poly(3-alkylthiophene)s decreased rapidly below the temperature at which the drift charge mobility was $10^{-5}\;cm^2/V{\cdot}s$.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2005.11a
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• pp.305-306
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• 2005

The effects of As addition In amorphous selenium (a-Se) films for digital X-ray conversion material have been studied using the moving photocarrier grating (MPG) technique We have found an increase in hole drift mobility and recombination lifetime, especially when 0.3% As is added into a-Se film, whereas electron mobility decreases with As addition due to the defect density. The transport properties for As doped a-Se films obtained by using MPG technique have been compared with X-ray sensitivity for a-Se:As X-ray device. The fabricated a-Se (0.3%As) based X-ray detector exhibited the highest X-ray sensitivity of 5 samples.