Understanding the chemical reaction pathway of the metal–salt precursor is essential for modifying the properties of solution-processed metal-oxide thin films and further improving their electrical performance. In this study, we focused on the structural growth of solution-processed amorphous indium-zinc-oxide (a-IZO) films and the electrical behavior of a-IZO thin-film transistors (TFT). To this end, solution-processed a-IZO films were prepared with respect to the Zn molar ratio, and their structural characteristics were analyzed. For the structural characteristic analysis of the a-IZO film, the cross-section, morphology, crystallinity, and atomic composition characteristics were used as the measurement results. Furthermore, the chemical reaction pathway of the nitrate precursor-based IZO solution was evaluated for the growth process of the a-IZO film structure. These interpretations of the growth process and chemical reaction pathway of the a-IZO film were assumed to be due to the thermal decomposition of the IZO solution and the structural rearrangement after annealing. Finally, based on the structural/chemical results, the electrical performance of the fabricated a-IZO TFT depending on the Zn concentration was evaluated, and the electrical behavior was discussed in relation to the structural characteristics.

Organic phototransistors capable of absorbing in the visible light spectrum without color filters are the best alternatives to conventional inorganic phototransistors. In this study, the effect of illumination on the electrical characteristics of a solution-processed poly(3-hexylthiophene): 6,13-bis(triisopropylsilylethynyl) pentacene-blend thin-film transistor (TFT) was investigated. The wavelengths of the irradiated light were determined from the absorbance spectrum of the blended film and changes in the transistor’s electrical characteristics were explained in relation to the electrical and light absorption properties of each component material. The photosensitivity and absorbing properties of the blended TFT were enhanced at 515 and 450 nm and exhibited positively shifted threshold voltages under incident light. The results indicated that the photo-generated exci-ton pair characteristics matched the absorbance properties of the blended material and that the absorption and photocurrent characteristics of the respective components could be combined. This process for the heterogeneous blending of organic semiconductors has the potential to improve phototransistor performance and contribute to the development of broadband absorbing phototransistors.

We investigate the electrical characteristics of solution-processed poly(3-hexylthiophene-2,5-diyl) (P3HT) thin-film transistors (TFTs) under monochromatic illumination conditions at different wavelengths of 700, 655, 515, and 315 nm. The TFT characteristics measured under light illumination at the wavelengths of 700 and 655 nm were comparable to those measured in the dark state. In addition, light illumination at a wavelength of 515 nm, of which photon energy (~2.4 eV) is higher than the band gap energy of P3HT (~1.7 eV), had a little effect on the electrical characteristics of P3HT TFTs. On the other hand, the TFT performance was notably changed by light illumination at a wavelength of 315 nm. These results indicate that the photon energy, which cause the characteristic degradation in the solution-processed P3HT TFTs, is much higher than the band gap energy of P3HT. Consequently, the illumination-induced variation in the TFT performance can be understood through a broad distribution of energetic states in the solution-processed P3HT semiconductor.

The electrical characteristics of solution‐processed Poly(3‐hexylthiophene) and 6,13‐bis(triisopropylsilylethynyl)pentacene blend thin‐film transistors were investigated under various light irradiation wavelengths. We present the phototransistor that improved photoelectric effect through heterogeneous blending and expands the absorption region.

Current injection behavior for QLEDs was theoretically analyzed, assuming traps are in Gaussian distribution in energy levels. The effects of several key factors on the carrier injection behavior was investigated. Our calculated results show that modulating parameters including Schottky barrier is not effective way to to enhance the efficacy of QLEDs.

The electrical properties of solution-processed 6,13-bis(triisopropylsilylethynyl)pentacene thin-film transistors were investigated under various light irradiation wavelengths. Irradiated light conditions were determined from wavelengths with specific peaks in the absorbance spectrum of the film, and changes in electrical characteristics were analyzed under light irradiation at these wavelengths. At long wavelengths of 695, 640, and 585 nm, a small number of photo-generated excitons lowered the hole injection barrier. At short wavelengths of 450 and 340 nm, a large number of photo-generated excitons threatened the electrically accumulated holes, lowering the decrease in threshold voltage variation. Furthermore, results including the content of the films based on light intensity, according to irradiated wavelengths are presented.

Studies of the pattern-formation technique used with solution-processed oxide thin-film transistors (TFTs) continue to explore its uses as an efficient manufacturing method. However, research remains to be completed to achieve high performance and to apply the refined technique to various current industrial technologies. We studied the patterning technique of solution-processed indium-zinc-oxide (IZO) by using the capillary-force phenomenon, the method of controlling the pattern of the IZO semiconductor layer, and approaches to reducing problems such as the cracking that occurs during patterning. The device we fabricated was filled uniformly with droplets in the capillary-force pattern. It showed a high current-on/current-off ratio, high mobility, low threshold voltage, and low subthreshold slope. Consequently, this paper demonstrates a strategy that uses the capillary-force-pattern technique to exceed the performance of traditional fabrication techniques in managing the electrical properties of solution-processed oxide TFTs.

In this work, we attempted to develop a new PI film bonding and mechanical detaching process which may be capable of replacing conventional PI film forming process, i.e., vanish coating followed by a thermal curing process and then laser lift‐off process. The new process developed showed that the mechanical detaching force is similar to that of laser lift‐off process.

We investigated the color conversion characteristics of a quantum dot/organic light-emitting diode (QD/OLED) by altering blue emission using the microcavity effect. Compared to the ITO-based OLED, the WO3/Ag/WO3 (WAW)-based OLED has a narrow shape of resonance and high cavity enhancement factor. As a result, the peak emission intensity wavelength remarkably shifts as the thickness of the WO3 layer increases and the WAW-based OLED with inner WO3 thickness of 120 nm shows an additional emission peak at 420 nm due to the second resonance. As the thickness of the WO3 layer increases, the color coordinates of the hybrid QD/OLED with the ITO anode are nearly unchanged. However, hybrid WAW-based devices exhibit distinct color coordinates, such as nearly blue light, nearly green light and nearly white light with color coordinates of (0.31, 0.37).

Two photo‐fragment activators, AAP and CAP, were synthesized as an additive, and applied for enhancement of azimuthal anchoring energy. During the ultraviolet (UV) exposure, created radicals from each activator generated carbon dioxide, and the surfaces became rough and hard by effects of the gas elimination. Understandably, we studied changes of surface morphology according to the UV exposure and tried to investigate the correlation of liquid crystal alignment with the changes of surface morphology.

This work presents a solution processing method of IZO TFTs through photocatalytic reactions of TiO2 to improve electrical properties. The mobility and on‐off current ratio increased from 0.35 to 1.21 cm2/Vs and from 106 to 107, respectively. By recycling the solution, the possibility of eco‐friendly oxide TFTs is demonstrated.

In order to improve the device performances of organic electroluminescent devices (OELDs), the efficiency of carrier injections into the organic layers from electrodes and the balance of injected carrier densities in the emission region are critical factors. Especially, energy barriers, which exist at the interfaces between electrodes and organic layers, interrupt carrier injections, which lead to unbalanced carrier densities. In this study α-septithiophene (α-7T), as a buffer layer, and composite cathode composed of Al and CsF were formed to improve hole and electron injections, respectively. The orientations of α-7T molecules were adjusted using the simple rubbing method and the mass ratio of CsF was varied from 1 to 10 wt

Organic phototransistors have been extensively studied because of their potential applications in electronic devices. In particular, organic-inorganic hybrid materials have attracted significant attention due to the possibility of combining solution processing of organic materials with high photon-to-current conversion efficiency of inorganic materials. In this study, a TIPS pentacene/TiO2 nanocomposite thin-film transistor (TFT) was fabricated as an organic/inorganic hybrid photo-transistor with high responsiveness to light, as compared to that for pristine TIPS pentacene TFT. It was found that the threshold voltage of the pristine TIPS pentacene TFT was shifted with an increase in the drain current under light irradiation. The observed shift was more pronounced for the composite TFT; however, it was also accompanied by a simultaneous decrease in the drain current, which could be explained in terms of the photovoltaic and photoconductive effects. The obtained results are able to characterize the photoresponsive behavior of the produced TIPS pentacene/TiO2 composite material under illumination.

We present a general principle of topography-directed (TD) inkjet printing for functional micro-tracks embedded in a flexible elastomer substrate. The essential features of the TD inkjet printing in a micro-structured substrate with periodic grooves and ridges are described in terms of the topographic parameters for the transformation from a single droplet to a filament or an edge-disjoint pattern of ink in the groove. Silver ink, being widely used for producing conductive wires by conventional inkjet printing, is utilized as a testbed in our study. The underlying mechanisms for the spreading and drying processes of ink drops under the topographic compartment can be understood in a two-dimensional parameter space of the aspect ratio of the groove and the contact angle of ink on the substrate. The wetting morphologies of ink droplets are described in an analytical model where the Laplace pressure and the mean curvature at the vapor/ink interface are taken into account. The first principle of the TD inkjet printing would be applicable for constructing a variety of functional micro-tracks with high pattern fidelity from different classes of solutions such as conducting polymers, organic semiconductors, and colloidal nanoparticles.

We demonstrated self‐patternable InZnO (IZO) thin‐film transistors (TFTs) using photosensitive precursors. UV‐irradiated films became cross‐linked and solution‐processed IZO films were patterned successfully. Compared to self‐patterned IZO TFTs using photosensitive activators, precursor‐based self‐patterned IZO TFTs have better electrical characteristics and stability due to having less organic residues.

Pressure and molecular-weight dependences of acoustic mode behaviors of polystyrene polymeric material were investigated by using Brillouin spectroscopy. The longitudinal, the transverse and the bulk sound velocities were measured over a wide pressure range from ambient pressure to more than 10 GPa for five polystyrene polymers whose molecular weight ranging from 3700 to 979200. The longitudinal and the bulk sound velocities displayed nearly the same pressure dependence for all polystyrenes indicating that the effective free volume is very similar in five polystyrene polymers despite the huge change in the molecular weight. The Poisson's ratio slightly increased with decreasing molecular weight. (C) 2017 Elsevier B.V. All rights reserved.

An ultra-fast and simple method for forming high-performance metal oxide semiconductor by a solution process based on sol–gel condensation in ambient air using pulse ultraviolet-light annealing is proposed for the thin-film transistor (TFT) application. Even a small amount of light absorbance by the transparent metal oxide film provide sufficient energy to carry out sol–gel condensation because of the extremely high peak energy and broad irradiation spectrum of the xenon lamp used in this study. The fabricated indium zinc oxide TFTs had a field-effect mobility of 2.4 cm2 V−1 s−1, which is comparable to a device performance of 2.7 cm2 V−1 s−1 obtained through thermal annealing.

We proposed a simple dipping method for improving positive bias stability of indium gallium zinc oxide (IGZO) thin-film transistors (TFTs) with homogeneous single layer using hydrogen peroxide solution which has strong oxidation potential. The stability and field-effect mobility of IGZO TFTs were significantly improved by controlling dipping time.

In this study, the environmental dependence of the electrical stability of solution-processed n-channel zinc tin oxide (ZTO) thin-film transistors (TFTs) is reported. Under a prolonged negative gate bias stress, a negative shift in threshold voltage occurs in atmospheric air, whereas a negligible positive shift in threshold voltage occurs under vacuum. In the positive bias-stress experiments, a positive shift in threshold voltage was invariably observed both in atmospheric air and under vacuum. In this study, the negative gate-bias-stress-induced instability in atmospheric air is explained through an internal potential in the ZTO semiconductor, which can be generated owing to the interplay between H2O molecules and majority carrier electrons at the surface of the ZTO film. The positive bias-stress-induced instability is ascribed to electron-trapping phenomenon in and around the TFT channel region, which can be further augmented in the presence of air O-2 molecules. These results suggest that the interaction between majority carriers and air molecules will have crucial implications for a reliable operation of solution-processed ZTO TFTs.