Smart windows are used as windows and doors to determine the cooling and heating efficiency of a building. They have characteristics that can increase the energy efficiency of a building, which leads to energy savings. In addition, smart windows can control the amount of light transmitted from the external environment of a building to the interior of a building according to the needs of the user. In this study, a 297×210 mm² liquid crystal cell capable of controlling light transmittance was fabricated using a liquid crystal device as an optical shutter. The effect of driving voltage on the transmittance and the effect of the thermal environment on the driving stability were analyzed. We confirmed the applicability of using smart windows as exterior building materials.

We investigated the effect of a post-annealing process using ultraviolet (UV) light on the electrical properties of solution-processed InZnO (IZO) thin-film transistors (TFTs). UV light was irradiated on IZO TFTs for different time periods of 0s, 30s, and 90s. We measured transfer and retention stability curves to evaluate the performance of the fabricated TFTs. In addition, we measured height, amplitude, and phase AFM images to analyze changes in the surface and morphology of the devices. AFM measurements were performed by setting the drive amplitude of the cantilever tip to 47.9 mV in tapping mode, then dividing the device surface into 500 nm × 500 nm. In the case of IZO TFT irradiated with UV for 30s, the electron mobility and Ion/Ioff ratio were improved, the threshold voltage was reduced by approximately 2 V, and the subthreshold swing also decreased form 1.34 V/dec to 1.11 V/dec.

The alignment characteristics of liquid crystal (LC) molecules on a solution-derived lanthanum zinc oxide (LZO) film under ion-beam irradiation were demonstrated. Using the solution process, an LZO film was fabricated on the glass substrate and cured at 100℃. Afterwards, ion-beam irradiation was performed following the LC alignment method. Using this film, an LC cell was fabricated and the characteristics of the LC alignment were verified. Cross polarizing microscopy and the crystal rotation method were used to investigate the alignment state of the LC molecules on the LZO films. Furthermore, field emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to explore the effect of the ion-beam irradiation on the LZO film. Through these, it was confirmed that the ion-beam irradiation induced surface modification, which demonstrated anisotropic physical and chemical surface characteristics. Due to this, uniform LC alignment was achieved. Finally, the residual DC and anchoring energy of the LC cell based on the LZO films were measured using a capacitance-voltage curve.

In this work, we investigate the effects of lithium doping on the electric performance of solution-processed n-type zinc tin oxide (ZTO)/p-type silicon carbide (SiC) heterojunction diode structures. The proper amount of lithium doping not only affects the carrier concentration and interface quality but also influences the temperature sensitivity of the series resistance and activation energy. We confirmed that the device characteristics vary with lithium doping at concentrations of 0, 10, and 20 wt%. In particular, the highest rectification ratio of 1.89×107 and the lowest trap density of 4.829×1,022 cm^-2 were observed at 20 wt% of lithium doping. Devices at this doping level showed the best characteristics. As the temperature was increased, the series resistance value decreased. Additionally, the activation energy was observed to change with respect to the component acting on the trap. We have demonstrated that lithium doping is an effective way to obtain a higher performance ZTO-based diode.

In this study, a femtosecond laser pre-annealing technology based on indium zinc oxide (IZO) thin-film transistors (TFTs) was investigated. We demonstrated a stable pre-annealing process to analyze the change in the surface structures of thin-films, and we improved the electrical performance. Furthermore, static and dynamic electrical characteristics of IZO TFTs with n-channel inverters were observed. To investigate the static and dynamic responses of our solution-processed IZO TFTs, simple resistor-load-type inverters were fabricated by connecting a 1-MΩ resistor. The femtosecond laser pre-annealing process based on IZO TFTs showed good performance: a field-effect mobility of 3.75 cm₂/Vs, an I_on/I_off ratio of 1.8×10⁵, a threshold voltage of 1.13 V, and a subthreshold swing of 1.21 V/dec. Our IZO-TFT-based N-MOS inverter performed well at operating voltage, and therefore, is a good candidate for advanced logic circuits and display backplane.

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 7.9 cm²/Vs, threshold voltage of 1.4 V, sub-threshold slope of 0.5 V/dec, and a current on/off ratio of 2.9×10⁷ 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 10 MΩ). Our IZO TFTs, which were manufactured using the soft baking process at a baking temperature of 120℃, performed well at the operating voltage, and are therefore a good candidate for use in advanced logic circuits and transparent display backplanes.

Ultraviolet (UV) photodetectors are used in various industries and fields of research, including optical communication, flame sensing, missile plume detection, astronomical studies, biological sensors, and environmental research. However, general UV detectors that employ Schottky junction diodes and p^-n junctions have high fabrication cost and low quantum efficiency. In this study, we investigated the characteristics of materials used to manufacture UV photodetectors in a low-cost solution process that requires easy fabrication of flexible substrates. We fabricated p-type NiO and n-type ZnO substrates with wide band gap by the sol^-gel method and compared the characteristics of substrates prepared under different spin-coating and heat-treatment conditions.

Zinc sulphide (ZnS) nanoparticles were fabricated by hydrothermal synthesis at 180℃ for 12 h. Two kinds of ZnS powder (hydrothermal synthesized ZnS and commercial ZnS) were investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) for phase and microstructure, respectively. The XRD patterns showed that all ZnS nanoparticles have a sphalerite (cubic) structure. The nanoparticles of two different ZnS powders were sintered by spark plasma sintering. The sintered ZnS were analyzed by XRD, SEM, and FT-IR. We found that the transmittance of the infrared region is highly dependent on the density and crystal structure of sintered ZnS and the purity of the starting ZnS powder.

In this study, the effects of soft baking temperature on the solution derived ZTO (Zn-Sn-O) TFTs (thin-film transistors) as a In-free oxide semiconductor were investigated. In spite of the same hard baking at high temperature(600℃), the electrical properties of ZTO TFT was greatly changed by a small difference in soft baking temperature(180~250℃). The performance of TFT was deteriorated as the soft baking temperature increased. Therefore, it is important to remove the water-related defects well as organic impurities from the ZTO films during soft baking for fabrication of solution-derived high performance of TFTs.

We investigated the effects of annealing on the electrical and thermal properties of ZTO/4H-SiC heterojunction diodes. A ZTO thin film layer was grown on p-type 4H-SiC substrate by using solution process. The ZTO/SiC heterojunction structures annealed at 500℃ show that Ion/Ioff increases from ~5.13×107 to ~1.11×109 owing to the increased electron concentration of ZTO layer as confirmed by capacitance-voltage characteristics. In addition, the electrical characterization of ZTO/SiC heterojunction has been carried out in the temperature range of 300∼500 K. When the measurement temperature increased from 300 K to 500 K, the reverse current variation of annealed device is higher than as-grown device, which is related to barrier height in the ZTO/SiC interface. It is shown that annealing process is possible to control the electrical characteristics of ZTO/SiC heterojunction diode.

Spinel thin films were prepared by the spin spray technique to develop new thermal imaging materials annealed at low temperature for uncooled microbolometer applications. The spinel thin films were deposited from [(Ni0.30Co0.33Mn0.37)1-xCux]3O4 (0.1≤x≤0.2) solutions and then annealed at 400℃ for 1 h inargon. Effects of Cu content (x) and deposition time on the electrical properties of the annealed films were investigated. With increasing deposition time, the resistivity of the annealed films increased. For the annealed films deposited for 1 min, the resistivity of x=0.15 films was lower than that of x=0.1 films due to the different grain sizes. The high temperature coefficient of resistance (TCR) of the annealed films could be obtained at temperature below 50℃. Typically, the resistivity of 127 Ω·cm and TCR of -5.69%/Kat 30℃ were obtained for x=0.1 films with deposition time of 1 min annealed at 400℃ for 1 h in argon.

[(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 (0≤x≤1) thin films prepared by metal organic decomposition process were fabricated on SiN/Si substrate for infrared sensor application. Their structural and electrical properties were investigated with variation of Cu dopant. The [(Co1-xCux)0.2(Ni0.3Mn0.7)0.8]3O4 (CCNMO) film annealed at500℃ exhibited a dense microstructure and a homogeneous crystal structure with a cubic spinel phase. Theircrystallinity was further enhanced with increasing doped Cu amount. The 120 nm-thick CCNMO (x=0.6) thin film had a low resistivity of 53 Ω·cm at room temperature while the Co-free film (x=1) showed a significantly decreased resistivity of 5.9 Ω·cm. Furthermore, the negative temperature coefficient of resistance(NTCR) characteristics were lower than -2%/℃ for all the specimens with x≥0.6. These results imply that the CCNMO (x≥0.6) thin films are a good candidate material for infrared sensor application.

We herein present results of flat and uniform polymer-blended small molecular semiconductor thin films. Which were produced for organic thin film transistors (OTFTs), using a simple pre-metered horizontal dipping process. The organic semiconducting thin films were composed of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS-PEN) composite blended with a polymer binder of poly(α-methylstyrene) (PaMS). We show that the pre-metered horizontal-dip-coating(H-dip-coating) process allowed the critical control of the thickness of the blended TIPS-PEN:PaMs thin film. The fabricated OTFTs using the TIPS-PEN:PaMs films exhibited maximum field-effect mobility of 0.22 cm2 V-1 s-1. These results demonstrated that H-dip-coated TIPS-PEN:PaMS films show considerable promise for the production of reliable, reproducible, and high-performance OTFTs.

In this paper, the properties of SnZnO films obtained from solution process with different component fractions were compared. The thermal behavior of the SnZnO solutions showed only a slight change according to the component fraction change. However, the definite changes were revealed at the structural properties of the SnZnO films. With diverse analyses, the origin of the changes was proved to the influence of phase change from SnO2 to ZnO in SnZnO lattice. With the SnO2-phase-dominant SnZnO, the highest field effect mobility and on/off ratio of about 8.6 cm2/Vs and 2 × 108 were achieved, respectively.

Soution-processed ZrInZnO (ZIZO) thin-film transistors (TFTs) with varying Zr content were fabricated. The ZIZO TFT (Zr=20 at. %/Zn) has an optimal performance with the saturation field effect mobility of 0.77 cm2/Vs, the threshold voltage (Vth) of 2.1 V, the on/off ratio of 4.95×10(6), and subthreshold swing (S.S) of 0.73 V/decade. Using this optimized ZIZO TFT, the positive and negative gate bias stress according to annealing temperature was also investigated. While the Vth shifts dramatically after 1,000 s of both gate bias stresses, variations in the S.S are negligible. It suggests that electrons or holes are temporarily trapped in the gate insulator, the semiconductor, or the interface between both layers.