• Current Applied Physics
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• v.18 no.11
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• pp.1415-1421
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• 2018

Unlike ordinary organic field-effect transistors (OFETs), saturation current is hardly to be found in vertical OFETs (VOFETs). Moreover, the fabrication process of patterned sourced for VOFETs is quite complex. In this current work, a simple solution processed VOFET with directly deposited intermediate silver source electrode has been demonstrated. The VOFET exhibits a high leakage current that induces an inversion polarity of its transistor behavior. Interestingly, a well-defined saturation current was observed in the linear scale of transfer characteristic. The VOFET operated with high-current density > $280mA/cm^2$ at $V_d=5V$. Overview potential of the fabricated device in display application is also presented. This preliminary work does open-up a new direction in VOFET fabrication and their application.

• Proceedings of the Materials Research Society of Korea Conference
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• 2007.11a
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• pp.17.1-17.1
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• 2007

• Polymer Science and Technology
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• v.21 no.4
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• pp.296-301
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• 2010

• Polymer Science and Technology
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• v.26 no.3
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• pp.232-237
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• 2015

• Bulletin of the Korean Chemical Society
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• v.33 no.11
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• pp.3645-3650
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• 2012

Two new blue emitting cationic iridium(III) complexes with two substituted 2-phenlypyridine ligands as main ligands and one 2,2'-biimidazole as an ancillary ligand, $[(L1)_2Ir(biim)]Cl$ (1) and $[(L2)_2Ir(biim)]Cl$ (2), where L1 = 2-(2',4'-difluorophenyl)-4-methylpyridine, L2 = 2-(2',4'-difluoro-3'-trifluoromethylphenyl)-4-methylpyridine and biim = 2,2'-biimidazole, were synthesized for applications in phosphorescent organic light-emitting diodes (PhOLEDs). Their photophysical, electrochemical and electroluminescent (EL) device performances were examined. The photoluminescent (PL) spectra revealed blue phosphorescence in the 450 to 485 nm range with a quantum yield of more than 10%. The iridium(III) compounds studied showed good solubility in organic solvents with no solvatochromism dependent on the solvent polarity. The solution-processed OLEDs were prepared with the configuration, ITO/PEDOT:PSS (40 nm)/mCP:Ir(III) (70 nm)/OXD-7 (20 nm)/LiF (1 nm)/Al (100 nm), by spin coating the emitting layer containing the mCP host doped with the iridium phosphors. The best performance of the fabricated OLEDs based on compound 1 showed an external quantum efficiency of 4.5%, luminance efficiency of 8.52 cd $A^{-1}$ and blue emission with the CIE coordinates (x,y) of (0.16, 0.33).

• Proceedings of the Korean Vacuum Society Conference
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• 2016.02a
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• pp.293.2-293.2
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• 2016

The In this paper, we have fabricated the solution processed In-Ga-ZnO thin film transistors (IGZO TFTs) by varying indium and gallium ratio. The indium ratio of IGZO TFTs was changed from 1 to 5 at fixed gallium and zinc oxide atomic percent of 1:1 and gallium ratio was varied from 1 to 5 at fixed indium and zinc oxide atomic percent of 1:1. When the indium ratio was increased at fixed gallium and zinc oxide ratio of 1:1, threshold voltage was negatively shifted from 1.03 to -6.18 V and also mobility was increased from 0.018 to $0.076cm2/V{\cdot}sec$. It means that the number of carriers in IGZO TFTs were increased due to great formation of the oxygen vacancies which generate electrons. In contrast, when the gallium ratio was increased in IGZO TFTs with indium and zinc oxide ration of 1:1, the on/off current ratio was increased from $1.88{\times}104$ to $2.22{\times}105$. It is because gallium have stronger chemical bonds with oxygen than that with the zinc and indium ions that lead to the decreased in electron concentration.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.30 no.9
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• pp.566-571
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• 2017

A soft baking process was used to enhance the electrical characteristics of solution-processed indium-zincoxide (IZO) thin-film transistors (TFTs). We demonstrate a stable soft baking process using a hot plate in air to maintain the electrical stability and improve the electrical performance of IZO TFTs. These oxide transistors exhibited good electrical performance; a field-effect mobility of $7.9cm^2/Vs$, threshold voltage of 1.4 V, sub-threshold slope of 0.5 V/dec, and a current on/off ratio of $2.9{\times}10^7$ were measured. To investigate the static response of our solutionprocessed IZO TFTs, simple resistor load type inverters were fabricated by connecting a resistor (5 or $10M{\Omega}$). Our IZO TFTs, which were manufactured using the soft baking process at a baking temperature of $120^{\circ}C$, performed well at the operating voltage, and are therefore a good candidate for use in advanced logic circuits and transparent display backplanes.

• Journal of Information Display
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• v.11 no.4
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• pp.165-168
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• 2010

A solution-processed multicomponent oxide, yttrium hafnium zinc oxide (YHZO), was synthesized and deposited as a gate insulator. The YHZO film annealed at $600^{\circ}C$ contained an amorphous phase based on the results of thermogravimetry, differential thermal analysis, and X-ray diffraction. The electrical characteristics of the YHZO film were analyzed by measuring the leakage current. The high dielectric constant (16.4) and high breakdown voltage (71.6 V) of the YHZO films resulted from the characteristics of $HfO_2$ and $Y_2O_3$, respectively. To examine if YHZO can be applied to thin-film transistors (TFTs), indium gallium zinc oxide TFTs with a YHZO gate insulator were also fabricated. The desirable characteristics of the YHZO films when used as a gate insulator show that the limitations of the general binary-oxide-based materials and of the conventional vacuum processes can be overcome.

• Transactions of the Korean hydrogen and new energy society
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• v.24 no.4
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• pp.282-287
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• 2013

Hydrogen production from water using solar energy is attractive way to obtain clean energy resource. Among the various solar-to-hydrogen production techniques, a combination of a photovoltaic and an electrolytic cell is one of the most promising techniques in term of stability and efficiency. In this study, we show successful fabrication of precursor solution processed CIGS thin film solar cells which can generate high voltage. In addition, CIGS thin film solar cell modules producing over 2V of open circuit voltage were fabricated by connecting three single cells in series, which are applicable to water electrolysis. The operating current and voltage during water electrolysis was measured to be 4.23mA and 1.59V, respectively, and solar to hydrogen efficiency was estimated to be 3.9%.

• Journal of the Korean Applied Science and Technology
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• v.30 no.2
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• pp.290-296
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• 2013

We analysed interfacial traps in organic thin-film transistors (TFTs) in which pentacene and 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-pentacene) organic semiconductors were deposited by means of vacuum-thermal evaporation and drop-coating methods, respectively. The thermally-deposited pentacene film consists of dentritic grains with the average grain size of around 1 m, while plate-like crystals over a few hundred microns are observed in the solution-processed TIPS-pentacene film. From the transfer characteristics of both TFTs, lower subthreshold slope of 1.02 V/decade was obtained in the TIPS-pentacene TFT, compared to that (2.63 V/decade) of the pentacene transistor. The interfacial trap density values calculated from the subthreshold slope are about $3.4{\times}10^{12}/cm^2$ and $9.4{\times}10^{12}/cm^2$ for the TIPS-pentacene and pentacene TFTs, respectively. Herein, lower subthreshold slope and less interfacial traps in TIPS-pentacene TFTs are attributed to less domain boundaries in the solution-processed TIPS-pentacene film.