• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.35 no.4
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• pp.366-371
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• 2022

Recently many efforts have been made to develop a novel class of non-fullerene electron acceptor materials for high-performance organic solar cells. In this work, anthraquinone derivatives, TMAQ and THAQ, were prepared and their availability as electron acceptor materials for organic solar cells were investigated in terms of optical, thermal, electrochemical properties, and solar cell devices. Compared to TMAQ, a significant bathochromic shift of absorption band was observed for THAQ owing to intramolecular hydrogen-bond-assisted CT interactions. Thanks to the fused aromatic ring structure and benzoquinone unit, both TMAQ and THAQ exhibited a high thermal stability and an efficient electron reduction process. In particular, the intramolecular O-H---O=C hydrogen bond of THAQ plays an important role in improving the thermal stability and electron reduction properties. In the P3HT:acceptor solar cell system, THAQ-based devices had more than ca. 6 times higher power conversion efficiency than TMAQ -based devices. These results serve as a guide for developing high-efficient anthraquinone-based electron acceptor materials.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.37 no.1
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• pp.1-10
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• 2024

Direct use of sunlight through the glass windows is an efficient way to reduce the energy consumption related to the heating, cooling, and lighting. Introduction of near-infrared modulating properties through colloidal doped metal oxide nanocrystals into the classical electrochromic materials accelerates the development of next-generation electrochromic devices. There has been a steady enhancement in the performance of electrochromic devices, necessitating a review of the recent progress in next-generation electrochromic devices employing doped metal oxide nanocrystals. This review provides an overview of the current developments in next-generation electrochromic smart windows utilizing colloidal doped metal oxide nanocrystals, with a focus on the key factors for achieving these advanced windows. Colloidal doped metal oxide nanocrystals are a crucial component in realizing and bringing to market the next generation of electrochromic windows, though further research and development are still required in this regard.

• International Journal of Internet, Broadcasting and Communication
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• v.15 no.4
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• pp.250-260
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• 2023

In this paper, we designed a IoT(Internet of Things) sensor block embedded lightweight house deck structures that can be implemented using Carbon Fiber Reinforced Polymer(CFRP). Deck-Sensor interconnection interface block via IoT connectivity Hub that can mount external environmental sensors such as fire sensors on the Deck body itself was also proposed. Additionally we described the configuration of devices for data acquisition and analysis based on IoT environmental detection sensors that can be commonly installed and used on these deck bodies. On the other hand, received sensing data based monitoring user interface(UI) also developed and used for sensing data analysis for remote monitoring center. Through the implementation of such IoT-based sensor data transmission and collection analysis devices and UI software, this paper confirmed the availability of CFRP based lightweight House deck structure and possibility of CFRP deck-based IoT sensor data networking and analysis functions.

• Journal of the Korea Convergence Society
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• v.8 no.1
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• pp.7-12
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• 2017

In this paper, we proposed an electronic attendance-absence recording system using a smartphone that does not require separate BLE(Bluetooth Low Energy) devices and infrastructure by using BLE advertisement technology of smartphone. The existing BLE-based electronic attendance-absence recording system requires a BEL device to be attached to each classroom for services and a separate technology to identify the devices attached to the classroom. Also, due to the interference with each other, sometimes an error occurred in the electronic connection. In this paper, we propose a system to solve the problems about time, place and cost, which is a disadvantage of the conventional Bluetooth beacon system. BLE advertising function of the smartphone that the user is using without BLE device, it is possible to construct infrastructure for electronic attendance-absence recording system. In order to evaluate the effectiveness of the proposed system, we designed the system structure and operation flow and constructed the system using the smart phone in actual used.

• Journal of the Semiconductor & Display Technology
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• v.14 no.1
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• pp.61-65
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• 2015

We have fabricated poly(3,4-ethylenedioxythiophene) : poly(4-styrenesulfonate) (PEDOT : PSS) thin films using a slotdie coater for the applications of OLED lightings. It is demonstrated that the properties of slot-die coated PEDOT : PSS films are comparable with those of spin-coated ones. Namely, the average and peak-to-peak roughness of the slot-die coated 50-nm-thick PEDOT : PSS film are measured to be as low as 0.247 nm and 1.3 nm, respectively. Moreover, we have obtained excellent thickness uniformity (~1.91%). With the slot-die coated PEDOT : PSS films, we have fabricated green phosphorescent OLED devices. For comparison, we have also fabricated OLED devices with spin-coated PEDOT : PSS films. Both show almost no discrepancy in device performance. The power efficiency (25.4 lm/W) and emission uniformity (77%) of OLEDs with slot-die coated PEDOT : PSS films are shown to be slightly lower than those (27.3 lm/W, 80%) of OLEDs with spin-coated PEDOT : PSS films at the luminance of 1,000nit, increasing the feasibility of using a slot-die coating process for the fabrication of large-area OLED lighting sources at a competitive price.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.19 no.5
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• pp.1213-1220
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• 2015

By the dissemination of the electronic blackboard systems, smart devices, and digital contents, the Korean government is recently conducting the project that replaces the classic education which utilizes paper textbooks with SMART education using various devices. Also, teachers in the field must be easily able to use SMART education infrastructure for the activation of SMART education. Especially, since the electronic blackboard is expected as a education device which will be most common for teachers, the writing software operated on the this device must supports a simple interface. And the usage of it must be simple. In this paper, we developed the writing software for the electronic blackboard which everyone can use easily. Our writing software supports the basic writing function, the human gesture recognition function which recognizes the user gesture and performs works corresponding with that gesture, and the automatic button alignment function based on the frequency of the usages.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2010.03a
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• pp.21-21
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• 2010

(Ba,Sr)$TiO_3$ (BST) thin film with a perovskite structure has potential for the practical application in various functional devices such as nonvolatile-memory components, capacitor, gate insulator of thin-film transistors, and electro-optic devices for display. Normally, the BST thin films derived from sol-gel and sputtering are amorphous or partially crystalline when processed below $600^{\circ}C$. For the purpose of integrating BST thin film directly into a Si-based read-out integrated circuit (ROIC), it is necessary to process the BST film below $400^{\circ}C$. The microstructural and electrical properties of low-temperature crystallized BST film were studied. The BST thin films have been fabricated at $350^{\circ}C$ by UV-assisted rapidly thermal annealing (RTA). The BST films are in a single perovskite phase and have well-defined electrical properties such as high dielectric constant, low dielectric loss, low leakage current density, and high breakdown voltage. Photoexcitation of the organics contained in the sol-gel-derived films by high-intensity UV irradiation facilitates elimination of the organics and formation of the single-crystalline phase films at low temperatures. The amorphous BST thin film was transformed to a highly (h00)-oriented perovskite structure by high oxygen pressure processing (HOPP) at as low as $350^{\circ}C$. The dielectric properties of BST film were comparable to (or even better than) those of the conventionally processed BST films prepared by sputtering or post-annealing at temperature above $600^{\circ}C$. When external pressure was applied to the well-known contractive BST system during annealing, the nucleation energy barrier was reduced; correspondingly, the crystallization temperature decreased. The UV-assisted RTA and HOPP, as compatible with existing MOS technology, let the BST films be integrated into radio-frequency circuit and mixed-signal integrated circuit below the critical temperature of $400^{\circ}C$.

• Journal of Power Electronics
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• v.15 no.4
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• pp.1105-1118
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• 2015

Battery energy storage devices (ESDs) have become more and more commonplace to maintain the stability of islanded power systems. Considering the limitation in inverter capacity and the requirement of flexibility in the ESD, the droop control was implemented in paralleled ESDs for higher capacity and autonomous operation. Under the conventional droop control, state-of-charge (SoC) errors between paralleled ESDs is inevitable in the discharging operation. Thus, some ESDs cease operation earlier than expected. This paper proposes an adaptive accelerating parameter to improve the performance of the SoC error eliminating droop controller under the constraints of a microgrid. The SoC of a battery ESD is employed in the active power droop coefficient, which could eliminate the SoC error during the discharging process. In addition, to expedite the process of SoC error elimination, an adaptive accelerating parameter is dedicated to weaken the adverse effect of the constraints due to the requirement of the system running. Moreover, the stability and feasibility of the proposed control strategy are confirmed by small-signal analysis. The effectiveness of the control scheme is validated by simulation and experiment results.

• Journal of the Semiconductor & Display Technology
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• v.21 no.2
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• pp.85-89
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• 2022

We reported on annealing effect on Ga₂O₃/Al₂O₃/SiC devices grown by radio frequency sputtering method. Post-deposition annealing at 900 ℃ was performed, which results in crystallization in the Ga₂O₃ films. The major peaks (-401) and (403) of Ga₂O₃ which was thermally treated at 900 ℃ appears in the x-ray diffraction (XRD) results. Auger electron spectroscopy (AES) shows that Ga and Al atoms seems to be diffused into the opposite direction Al₂O₃ and Ga₂O₃ after annealing. Transfer and output characteristics of back-gate transistor were analyzed where SiC substrate is used as gate material. On-state current and on/off ratio increased almost 10⁹ and 10⁶ times higher in the 900 ℃ annealed sample.

• Journal of the Korean Applied Science and Technology
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• v.40 no.1
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• pp.179-187
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• 2023

Nanogenerators containing biomaterials are eco-friendly electronic devices in terms of being a non-polluting energy source and biodegradable electronic waste. In particular, the amount of waste will be also reduced if the biomaterial can be extracted from biowaste. In this study, a triboelectric nanogenerator was fabricated using animal collagen present in the skin of a mammal and its characteristion was proformed. The electro-anodic layer of the triboelectric nanogenerator was constructed by forming a collagen film using the spin coating method, and it was confirmed that the film was porous from scanning electron microscopy. The fabricated triboelectric nanogenerator exhibited an open-circuit voltage from 7 V at 3 Hz to 15 V at 5 Hz due to periodic mechanical movement, and a short-circuit current of 3.8 uA at 5 Hz. In conclusion, collagen-containing triboelectric nanogenerators can be power source for low-power operating devices such as sensors and are also expected to be useful for reducing electronic waste.