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Flexible artificial synesthesia electronics with sound-synchronized electroluminescence
Kim, Jong Sung,Cho, Sung Hwan,Kim, Kang Lib,Kim, Gwangmook,Lee, Seung Won,Kim, Eui Hyuk,Jeong, Beomjin,Hwang, Ihn,Han, Hyowon,Shim, Wooyoung,Lee, Tae-Woo,Park, Cheolmin Elsevier 2019 Nano energy Vol.59 No.-
<P><B>Abstract</B></P> <P>Visualization of human senses has been of great interest for developing an emerging interactive display that can artificially stimulate synesthesia with numerous unprecedented applications. Especially, visualization of various daily sound and music, which are much more complicated than human touch, in a form of flexible thin film devices can be a great challenge. We present flexible artificial synesthesia electronics that visualize continuous and complicated sounds. The electronic device is made of a thin composite film of a piezoelectric polymer for sound generation and inorganic electroluminescence (EL) microparticles for direct visualization of input sound signals. Field-induced EL of the microparticles in the device depends upon the source sound wave, making their EL synchronized with sound arising from the piezoelectric actuation. The flexible artificial synesthesia devices with sound-synchronized EL (FASSEL) showed extreme mechanical tolerance that can be repeatedly folded and crumpled with visible sound, allowing a variety of unexplored applications including synchronous sound-lightings and wearable, on-body sound-vision systems to facilitate emotional interaction of human being with sound in a human-friendly form.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Ultra-flexible piezoelectric loudspeakers were developed with sound synchronized EL. </LI> <LI> Piezoelectric polymer composite with EL particles for direct visualization of sound. </LI> <LI> Artificial synesthesia of sound and vision via a single capacitive device platform. </LI> <LI> Silica-encapsulated-ZnS particle was employed for high EL with low leakage current. </LI> <LI> Extreme mechanical tolerance that can be repeatedly folded and crumpled. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
Kim, Changho,Ko, Youngsu,Kim, Taemin,Yoo, Chan-Sei,Choi, BeomJin,Han, Seung Ho,Jang, YongHo,Kim, Youngho,Kim, Namsu Techno-Press 2018 Smart Structures and Systems, An International Jou Vol.22 No.2
Increasing interest in prognostics and health management has heightened the need for wireless sensor networks (WSN) with efficient power sources. Piezoelectric energy harvesters using Pb(Zr,Ti)O3 (PZT) are one of the candidate power sources for WSNs as they efficiently convert mechanical vibration energy into electrical energy. These types of devices are resonated at a specific frequency, which has a significant impact on the amount of energy harvested, by external vibration. Hence, precise prediction of mechanical deformation including modal analysis of piezoelectric devices is crucial for estimating the energy generated under specific conditions. In this study, an experimental vibrational system capable of controlling a wide range of frequencies and accelerations was designed to generate mechanical vibration for piezoelectric energy harvesters. In conjunction with MATLAB, the system automatically finds the resonance frequency of harvesters. A small accelerometer and non-contact laser displacement sensor are employed to investigate the mechanical deformation of harvesters. Mechanical deformation under various frequencies and accelerations were investigated and analyzed based on data from two types of sensors. The results verify that the proposed system can be employed to carry out vibration experiments for piezoelectric harvesters and measurement of their mechanical deformation.
Titanium nitride thin film as a novel charge collector in TCO-less dye-sensitized solar cell
Yoo, Beomjin,Kim, Kang-Jin,Kim, Yong Hyun,Kim, Kyungkon,Ko, Min Jae,Kim, Won Mok,Park, Nam-Gyu Royal Society of Chemistry 2011 Journal of materials chemistry Vol.21 No.9
<P>A titanium nitride (TiN)-based dye-sensitized solar cell is developed where TiN is used as a charge collector and TCO-less glass as a substrate. A nanocrystalline TiO<SUB>2</SUB> film was deposited onto a TCO-less glass substrate using the radio frequency (r.f.) magnetron sputtering method and capped with a TiN film with a thickness of ∼66 to ∼167 nm, which was controlled by varying sputtering time. The crystal structure of TiN layers is analyzed using XRD, chemical bonding nature and composition (TiN<SUB>0.95</SUB>) were confirmed by XPS and RBS, respectively. Cross-sectional scanning electron microscopic images confirmed the columnar structure of TiN films. Electrical resistance is exponentially decayed and approaches 4.4 Ω as the TiN film thickness increases up to 167 nm. The photovoltaic property is significantly influenced by the TiN film thickness. The energy conversion efficiency increases from 3.3% to 6.8% with increasing the TiN film thickness from 66 nm to 86 nm, where an increase in fill factor from 0.33 to 0.64 is mainly responsible for the efficiency improvement. The highest efficiency of 7.4% is obtained with a 136 nm-thick TiN film and declines to 5.8% at 167 nm, resulting in a one order of magnitude retarded diffusion rate of I<SUB>3</SUB><SUP>−</SUP>. A long-term stability test was performed for 1000 h and compared with a cell with pure Ti metal. The TiN-based cell maintains an efficiency of 84% after 1000 h, while the efficiency of the Ti-based cell is degraded by ∼34%, indicating that TiN is more stable than Ti in the TCO-less dye-sensitized solar cell.</P> <P>Graphic Abstract</P><P>A titanium nitride material was used as a charge collector for the first time in the TCO-less dye-sensitized solar cell. It was found that TiN efficiently collected photo-injected electrons, where the best efficiency of 7.4% was achieved with a TiN thickness of 136 nm. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c0jm02962a'> </P>
Changho Kim,Youngsu Ko,Taemin Kim,유찬세,BeomJin Choi,한승호,YongHo Jang,Youngho Kim,Namsu Kim 국제구조공학회 2018 Smart Structures and Systems, An International Jou Vol.22 No.2
Increasing interest in prognostics and health management has heightened the need for wireless sensor networks (WSN) with efficient power sources. Piezoelectric energy harvesters using Pb(Zr,Ti)O3 (PZT) are one of the candidate power sources for WSNs as they efficiently convert mechanical vibration energy into electrical energy. These types of devices are resonated at a specific frequency, which has a significant impact on the amount of energy harvested, by external vibration. Hence, precise prediction of mechanical deformation including modal analysis of piezoelectric devices is crucial for estimating the energy generated under specific conditions. In this study, an experimental vibrational system capable of controlling a wide range of frequencies and accelerations was designed to generate mechanical vibration for piezoelectric energy harvesters. In conjunction with MATLAB, the system automatically finds the resonance frequency of harvesters. A small accelerometer and non-contact laser displacement sensor are employed to investigate the mechanical deformation of harvesters. Mechanical deformation under various frequencies and accelerations were investigated and analyzed based on data from two types of sensors. The results verify that the proposed system can be employed to carry out vibration experiments for piezoelectric harvesters and measurement of their mechanical deformation.
Park, Beomjin,Kim, Kyunghun,Park, Jaesung,Lim, Heeseon,Lanh, Phung Thi,Jang, A-Rang,Hyun, Chohee,Myung, Chang Woo,Park, Seungkyoo,Kim, Jeong Won,Kim, Kwang S.,Shin, Hyeon Suk,Lee, Geunsik,Kim, Se Hyun American Chemical Society 2017 ACS APPLIED MATERIALS & INTERFACES Vol.9 No.33
<P>Organic crystals deposited on 2-dimensional (2D) van der Waals substrates have been widely investigated due to their unprecedented crystal structures and electrical properties. van der Waals interaction between organic molecules and the substrate induces epitaxial growth of high quality organic crystals and their anomalous crystal morphologies. Here, we report on unique ambipolar charge transport of a 'lying-down' pentacene crystal grown on a 2D hexagonal boron nitride van der Waals substrate. From in-depth analysis on crystal growth behavior and ultraviolet photoemission spectroscopy measurement, it is revealed that the pentacene crystal at the initial growth stage have a lattice-strained packing structure and unique energy band structure with a deep highest occupied molecular orbital level compared to conventional 'standing-up' crystals. The lattice-strained pentacene few layers enable ambipolar charge transport in field-effect transistors with balanced hole and electron field-effect mobilities. Complementary logic circuits composed of the two identical transistors show clear inverting functionality with a high gain up to 15. The interesting crystal morphology of organic crystals on van der Waals substrates is expected to attract broad attentions on organic/2D interfaces for their electronic applications.</P>
Method to Protect Charge Recombination in the Back-Contact Dye-Sensitized Solar Cell
Yoo, Beomjin,Kim, Kang-Jin,Lee, Doh-Kwon,Kim, Kyungkon,Ko, Min Jae,Kim, Yong Hyun,Kim, Won Mok,Park, Nam-Gyu The Optical Society 2010 Optics express Vol.18 No.suppl3
<P>We prepared a back-contact dye-sensitized solar cell and investigated effect of the sputter deposited thin TiO??film on the back-contact ITO electrode on photovoltaic property. The nanocrystalline TiO??layer with thickness of about 11 관m formed on a plain glass substrate in the back-contact structure showed higher optical transmittance than that formed on an ITO-coated glass substrate, which led to an improved photocurrent density by about 6.3%. However, photovoltage was found to decrease from 817 mV to 773 mV. The photovoltage recovered after deposition of a 35 nm-thick thin TiO??film on the surface of the back-contact ITO electrode. Little difference in time constant for electron transport was found for the back-contact ITO electrodes with and without the sputter deposited thin TiO??film. Whereas, time constant for charge recombination increased after introduction of the thin TiO??film, indicating that such a thin TiO??film protected back electron transfer, associated with the recovery of photovoltage. As the result of the improved photocurrent density without deterioration of photovoltage, the back-contact dye-sensitized solar cell exhibited 13.6% higher efficiency than the ITO-coated glass substrate-based dye-sensitized solar cell.</P>
Kim, Beomjin,Song, Woo Chang,Park, Sun Young,Park, Geuntae The Korean Environmental Sciences Society 2020 한국환경과학회지 Vol.29 No.12
The green synthesis of inorganic nanoparticles (NPs) using biomaterials has garnered considerable attention in recent years because of its eco-friendly, non-toxic, simple, and low-cost nature. In this study, we synthesized NPs of noble metals, such as Ag and Au using an aqueous extract of a marine seaweed, Ecklonia cava. The formation of AgNPs and AuNPs was confirmed by the presence of surface plasmon resonance peaks in UV-Vis absorption spectra at approximately 430 and 530 nm, respectively. Various properties of the NPs were evaluated using characterization techniques, such as dynamic light scattering, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. Phytochemicals in the seaweed extract, such as phlorotannins, acted as both reducing and stabilizing agents for the growth of the NPs. The green-synthesized AgNPs and AuNPs were found to exhibit high catalytic activity for the decomposition of organic dyes, including azo dyes, methylene blue, rhodamine B, and methyl orange.