• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.9-10
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• 2006

The patterning for the active layer of organic semiconductors is important to attain completely organic-based OTFTs(Organic Thin Film Transistors). We studied on possibility of the application of the conventional photolithography technique to pattern the organic active layer poly(3-hexylthiophene)(P3HT). Patterned P3HT-based OTFTs with Bottom Contact(BC) configuration were fabricated using the conventional photolithography. We achieved field-effect mobilities in the saturation regime ${\sim}1.2{\times}10^{-3}cm^2/V{\cdot}s$, $I_{on/off}$ ratios ${\sim}10^5$ in the subtractive method, ${\sim}8{\times}10^{-4}cm^2/V{\cdot}s$, $I_{on/off}$ ratios ${\sim}10^3$ in the additive one.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.467-468
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• 2006

We report on the fabrication of P3HT-based thin-film transistors (TFT) that consist of indium-zinc-oxide (IZO), PVP (poly-vinyl phenol), and Ni for the source-drain (S/D) electrode, gate dielectric, and gate electrode, respectively. The IZO S/D electrodes of which the work function is well matched to that of P3HT were deposited on a P3HT channel by thermal evaporation of IZO and showed a moderately low but still effective transmittance of ~25% in the visible range along with a good sheet resistance of ${\sim}60{\Omega}/{\square}$. The maximum saturation current of our P3HT-based TFT was about $15{\mu}A$ at a gate bias of -40V showing a high field effect mobility of $0.05cm^2/Vs$ in the dark, and the on/off current ratio of our TFT was about $5{\times}10^5$. It is concluded that jointly adopting IZO for the S/D electrode and PVP for gate dielectric realizes a high-quality P3HT-based TFT.

• Proceedings of the Korean Vacuum Society Conference
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• 2012.08a
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• pp.163-163
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• 2012

We observed strain evolution of P3HT crystals in P3HT:PCBM films and the effect of Al electrode on the evolution during real time annealing process. Based on simple assumptions, both relaxed lattice parameters and thermal expansion coefficient could be quantitatively determined. P3HT:PCBM films displayed tensile strain in as-prepared samples regardless of the presence of an Al layer. In the absence of Al layer, P3HT crystals showed only strain relaxation at an annealing temperature of $180^{\circ}C$. Meanwhile In the presence of an Al layer, the strain was relaxed and changed to compressive strain at around 120C annealing temperature, which indicated a tightening of the thiophene ring packing. These behaviors support the improved performance of devices fabricated by post annealing process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.191-191
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• 2007

By employing a photo-sensitive PVA as a photoresist, we first demonstrated simultaneous patterning and passivation of P3HT active layer. The passivation layers were obtained by annealing the organic layers after developing PVA and over-etching the P3HT layer. The fabricated OTFTs were electrically characterized. The OTFTs after the passivation exhibited the field-effect of ${\sim}5.9{\times}10^{-4}cm^2/V{\cdot}s$, on/off current ratio of ${\sim}10^3$. The value of OTFTs a little degradation with time in air but it appeared different unpassivated OTFT.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.06a
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• pp.460-461
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• 2009

We studied the effects of post-annealing treatment on poly(3-hexylthiophene)(P3HT, donor):[6,6]-phenyl $C_{61}$ butyric acid methyl ester(PCBM, acceptor) blend film as an active layer in the organic solar cells(OSCs). For the formation of the active layer, 3 wt.% P3HT:PCBM solution in chlorobenzene were deposited by spin-coating method. In order to optimize the performance of OSCs, the P3HT crystallization and the redistribution of PCBM cluster at P3HT:PCBM composition as a function of post-annealing condition from room temperature to $200^{\circ}C$ were measured by the Hall effect and the UV-vis Spectrophotometer. We thought that the improved efficiency in the OSCs with post-annealing treatment at $150^{\circ}C$ can be explained by the efficient separation or collection of the photogenerated excitons at donor-acceptor interface by P3HT crystallization.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2002.04b
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• pp.45-48
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• 2002

Poly(3-hexylthiophene) or P3HT based organic thin film transistor (OTFT) array was fabricated on flexible poly carbonate substrates and the electrical characteristics were investigated. As the gate dielectric, a dual layer structure of polyimide-$SiO_2$ was used to improve the roughness of $SiO_2$ surface and further enhancing the device performance and also source-drain electrodes were $O_2$ plasma treated for improvement of the electrical properties, such as drain current and field effect mobility. For the active layer, polymer semiconductor, P3HT layer was printed by contact-printing and spin-coating method. The electrical properties of OTFT devices printed by both methods were evaluated for the comparison. Based on the experiments, P3HT-based OTFT array with field effect mobility of 0.02~0.025 $cm^{2}/V{\cdot}s$ and current modulation (or $I_{on}/I_{off}$ ratio) of $10^{3}\sim10^{4}$ was fabricated.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.21 no.5
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• pp.426-433
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• 2008

We first demonstrated simultaneous patterning and passivation of P3HT active layer with photosensitive PVA. The passivation layers were obtained by annealing the organic layers after developing PVA and subsequent over-etching the P3HT layer. The fabricated OTFTs were electrically characterized. The OTFTs exhibited the mobility of ${\sim}5.9{\times}10^{-4}\;cm^2/V{\cdot}s$ and on/off current ratio of ${\sim}10^4$. After passivation, the results showed the extended lifetime of ${\sim}250$ hours with photosensitive PVA layer.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1998.11a
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• pp.57-60
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• 1998

Poly(3-hexylthiophene)(P3HT) was synthesized by use of FeCl$_3$ as a oxidizing agent at $25^{\circ}C$. The infrared spectrum of our polymer gave good evidence for the conjugation of 3-hexylthiophene monomer unit. P3HT contains the HT(head-to-tail) linkage larger than 64% based on NMR analysis. Electronic absorption and photoluminescence studies show that cast films of P3HT have three exciting state. Absorption spectrum was separated with three maximum peaks by Giese-French method and shifted to the shorter wavelength with increasing temperature. Separated absorption spectrum of P3HT is well adapted to PL peak appeared at longer wavelength. Low temperature PL spectrum is well separated at 669nm, 733nm and 812nm.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.19 no.12
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• pp.1140-1143
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• 2006

We report on the fabrication of P3HT-based thin-film transistors (TFTs) for liquid crystal display that consist of $NiO_x$, poly-vinyl phenol (PVP), and Ni for the source-drain (S/D) electrodes, gate dielectric layer, and gate electrode, respectively The $NiO_x$ S/D electrodes of which the work function is well matched to that of P3HT are deposited on a P3HT channel by electron-beam evaporation of NiO powder. The maximum saturation current of our P3HT-based TFT is about $15{\mu}A$ at a gate bias of -30 V showing a high field effect mobility of $0.079cm^2/Vs$ in the dark, and the on/off current ratio of our TFT is about $10^5$. It is concluded that jointly adopting $NiO_x$ for the S/D electrodes and PVP for gate dielectric realizes a high-quality P3HT-based TFT.

• Journal of the Korean Academy of Child and Adolescent Psychiatry
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• v.12 no.2
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• pp.165-178
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• 2001

In order to elucidate the biological etiology and the relationship between the ontogenesis of serotonin system and psychopathology in ADHD, plasma serotonin(5-hydroxytryptamine, 5-HT) and 5-hydroxyindoleacetic acid(5-HIAA) were measured and the correlation between the plasma levels of 5-HT and 5-HIAA and age were evaluated in 46 ADHD patients and 18 control subjects. The ADHD patients were composed of 16 combined type, 10 inattentive type, and 20 hyperactive-impulsive type and the control subjects were communication disorders. The results are summarized as follows：1) There was significant difference in plasma 5-HT levels among combined, inattentive and hyperactive-impulsive and control subjects(ANOVA F=4.33, df 3, 60, p<0.05), and post-hoc test using Scheffe method showed significant difference between the combined type and control group. But, post-hoc tests showed no significant differences between combined and inattentive, combined and hyperactive-impulsive, hyperactive-impulsive and inattentive, hyperactive-impulsive and control and inattentive and control groups. 2) There was no significant differences in plasma 5-HIAA levels among the combined, hyperactive- impulsive, inattentive and control groups(ANOVA F=2.08, df 3, 60, p>0.05). 3) Significant difference in 5-HT level was found between the whole ADHD group(N=46) and the control group(N=18)(T=3.10, df 62, p<0.05). But no significant difference in 5-HIAA level was found between the whole ADHD group and the control group(T=1.90, df 62, p>0.05). 4) Plasma 5-HT and 5-HIAA levels showed no significant correlation with TOVA findings(5-HT：omission pearson correlation 0.10, commision 0.23, reaction time 0.01, variability in attention 0.11, all p>0.05, 5-HIAA：omission 0.21, commision 0.15, reaction time 0.09, variability in attention 0.15, all p>0.05). 5) Plasma 5-HT and 5-HIAA levels showed no significant correlation with attention, hyperactivity and impulsivity based on DSM-IV criteria. 6) Plasma 5-HT and 5-HIAA levels showed no significant correlation with age both in ADHD and control group. These findings show that decreased plasma 5-HT level may play a role in the genesis of ADHD, but this finding has no significant correlation with the psychopathology of ADHD. And we could not find any significant differences in ontogenetic processes in 5-HT. Future studies should be focused on the drug effects, family history and prognosis based on the biochemical subtypes(high and low 5-HT group).