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KAIST Develops Transparent Oxide Thin-Film Transistors
With the advent of the Internet of Things (IoT) era, strong demand has grown for wearable and transparent displays that can be applied to various fields such as augmented reality (AR) and skin-like thin flexible devices. However, previous flexible transparent displays have posed real challenges to overcome, which are, among others, poor transparency and low electrical performance. To improve the transparency and performance, past research efforts have tried to use inorganic-based electronics, but the fundamental thermal instabilities of plastic substrates have hampered the high temperature process, an essential step necessary for the fabrication of high performance electronic devices. As a solution to this problem, a research team led by Professors Keon Jae Lee and Sang-Hee Ko Park of the Department of Materials Science and Engineering at the KAIST has developed ultrathin and transparent oxide thin-film transistors (TFT) for an active-matrix backplane of a flexible display by using the inorganic-based laser lift-off (ILLO) method. Professor Lee’s team previously demonstrated the ILLO technology for energy-harvesting (Advanced Materials, February 12, 2014) and flexible memory (Advanced Materials, September 8, 2014) devices. The research team fabricated a high-performance oxide TFT array on top of a sacrificial laser-reactive substrate. After laser irradiation from the backside of the substrate, only the oxide TFT arrays were separated from the sacrificial substrate as a result of reaction between laser and laser-reactive layer, and then subsequently transferred onto ultrathin plastics ( thickness). Finally, the transferred ultrathin-oxide driving circuit for the flexible display was attached conformally to the surface of human skin to demonstrate the possibility of the wearable application. The attached oxide TFTs showed high optical transparency of 83% and mobility of even under several cycles of severe bending tests. Professor Lee said, “By using our ILLO process, the technological barriers for high performance transparent flexible displays have been overcome at a relatively low cost by removing expensive polyimide substrates. Moreover, the high-quality oxide semiconductor can be easily transferred onto skin-like or any flexible substrate for wearable application.” These research results, entitled “Skin-Like Oxide Thin-Film Transistors for Transparent Displays,” (http://onlinelibrary.wiley.com/doi/10.1002/adfm.201601296/abstract) were the lead article published in the July 2016 online issue of Wiley’s Advanced Functional Materials. ### References [1] Advanced Materials, February 12, 2014, Highly-efficient, Flexible Piezoelectric PZT Thin Film Nanogenerator on Plastic Substrates (http://onlinelibrary.wiley.com/doi/10.1002/adma.201305659/abstract) [2] Advanced Materials, September 8, 2014, Flexible Crossbar-structured Resistive Memory Arrays on Plastic Substartes via Inorganic-based Laser Lift-off (http://onlinelibrary.wiley.com/doi/10.1002/adma.201402472/abstract) Picture 1: A Schamatic Image of Ultrathin, Flexible, and Transparent Oxide Thin-film Transistors This image shows ultrathin, flexible, and transparent oxide thin-film transistors produced via the ILLO process. Picture 2: Application of Uultrathin, Flexible, and Transparent Oxide Thin-film Transistors This picture shows ultrathin, flexible, and transparent oxide thin-film transistors attached to a jumper sleeve and human skin.
2016.08.01
View 11237
Graphene-Based Transparent Electrodes for Highly Efficient Flexible OLEDs
A Korean research team developed an ideal electrode structure composed of graphene and layers of titanium dioxide and conducting polymers, resulting in highly flexible and efficient OLEDs. The arrival of a thin and lightweight computer that even rolls up like a piece of paper will not be in the far distant future. Flexible organic light-emitting diodes (OLEDs), built upon a plastic substrate, have received greater attention lately for their use in next-generation displays that can be bent or rolled while still operating. A Korean research team led by Professor Seunghyup Yoo from the School of Electrical Engineering, KAIST and Professor Tae-Woo Lee from the Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH) has developed highly flexible OLEDs with excellent efficiency by using graphene as a transparent electrode (TE) which is placed in between titanium dioxide (TiO2) and conducting polymer layers. The research results were published online on June 2, 2016 in Nature Communications. OLEDs are stacked in several ultra-thin layers on glass, foil, or plastic substrates, in which multi-layers of organic compounds are sandwiched between two electrodes (cathode and anode). When voltage is applied across the electrodes, electrons from the cathode and holes (positive charges) from the anode draw toward each other and meet in the emissive layer. OLEDs emit light as an electron recombines with a positive hole, releasing energy in the form of a photon. One of the electrodes in OLEDs is usually transparent, and depending on which electrode is transparent, OLEDs can either emit from the top or bottom. In conventional bottom-emission OLEDs, an anode is transparent in order for the emitted photons to exit the device through its substrate. Indium-tin-oxide (ITO) is commonly used as a transparent anode because of its high transparency, low sheet resistance, and well-established manufacturing process. However, ITO can potentially be expensive, and moreover, is brittle, being susceptible to bending-induced formation of cracks. Graphene, a two-dimensional thin layer of carbon atoms tightly bonded together in a hexagonal honeycomb lattice, has recently emerged as an alternative to ITO. With outstanding electrical, physical, and chemical properties, its atomic thinness leading to a high degree of flexibility and transparency makes it an ideal candidate for TEs. Nonetheless, the efficiency of graphene-based OLEDs reported to date has been, at best, about the same level of ITO-based OLEDs. As a solution, the Korean research team, which further includes Professors Sung-Yool Choi (Electrical Engineering) and Taek-Soo Kim (Mechanical Engineering) of KAIST and their students, proposed a new device architecture that can maximize the efficiency of graphene-based OLEDs. They fabricated a transparent anode in a composite structure in which a TiO2 layer with a high refractive index (high-n) and a hole-injection layer (HIL) of conducting polymers with a low refractive index (low-n) sandwich graphene electrodes. This is an optical design that induces a synergistic collaboration between the high-n and low-n layers to increase the effective reflectance of TEs. As a result, the enhancement of the optical cavity resonance is maximized. The optical cavity resonance is related to the improvement of efficiency and color gamut in OLEDs. At the same time, the loss from surface plasmon polariton (SPP), a major cause for weak photon emissions in OLEDs, is also reduced due to the presence of the low-n conducting polymers. Under this approach, graphene-based OLEDs exhibit 40.8% of ultrahigh external quantum efficiency (EQE) and 160.3 lm/W of power efficiency, which is unprecedented in those using graphene as a TE. Furthermore, these devices remain intact and operate well even after 1,000 bending cycles at a radius of curvature as small as 2.3 mm. This is a remarkable result for OLEDs containing oxide layers such as TiO2 because oxides are typically brittle and prone to bending-induced fractures even at a relatively low strain. The research team discovered that TiO2 has a crack-deflection toughening mechanism that tends to prevent bending-induced cracks from being formed easily. Professor Yoo said, “What’s unique and advanced about this technology, compared with previous graphene-based OLEDs, is the synergistic collaboration of high- and low-index layers that enables optical management of both resonance effect and SPP loss, leading to significant enhancement in efficiency, all with little compromise in flexibility.” He added, “Our work was the achievement of collaborative research, transcending the boundaries of different fields, through which we have often found meaningful breakthroughs.” Professor Lee said, “We expect that our technology will pave the way to develop an OLED light source for highly flexible and wearable displays, or flexible sensors that can be attached to the human body for health monitoring, for instance.” The research paper is entitled “Synergistic Electrode Architecture for Efficient Graphene-based Flexible Organic Light-emitting Diodes” (DOI. 10.1038/NCOMMS11791). The lead authors are Jae-Ho Lee, a Ph.D. candidate at KAIST; Tae-Hee Han, a Ph.D. researcher at POSTECH; and Min-Ho Park, a Ph.D. candidate at POSTECH. This study was supported by the Basic Science Research Program of the National Research Foundation of Korea (NRF) through the Center for Advanced Flexible Display (CAFDC) funded by the Ministry of Science, ICT and Future Planning (MSIP); by the Center for Advanced Soft-Electronics funded by the MSIP as a Global Frontier Project; by the Graphene Research Center Program of KAIST; and by grants from the IT R&D Program of the Ministry of Trade, Industry and Energy of Korea (MOTIE). Figure 1: Application of Graphene-based OLEDs This picture shows an OLED with the composite structure of TiO2/graphene/conducting polymer electrode in operation. The OLED exhibits 40.8% of ultrahigh external quantum efficiency (EQE) and 160.3 lm/W of power efficiency. The device prepared on a plastic substrate shown in the right remains intact and operates well even after 1,000 bending cycles at a radius of curvature as small as 2.3 mm. Figure 2: Schematic Device Structure of Graphene-based OLEDs This picture shows the new architecture to develop highly flexible OLEDs with excellent efficiency by using graphene as a transparent electrode (TE).
2016.06.07
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Professor Ki-Jun Jeong Wins the 2015 Dam Yeun Academic Award
The 11th Dam Yeun Academic Award presented by the Korean Society for Biotechnology and Bioengineering (KSBB) to a biologist under 45 years old went to Professor Ki-Jun Jeong of the Chemical and Biomolecular Engineering Department at KAIST. The award ceremony took place on October 13, 2015, at the annual conference of KSBB held at Songdo Convensia in Incheon City. Each year KSBB announces the recipient of the award based on the publications by researchers in the last five years at peer-reviewed international journals or KSBB Journal as well as the record of patent registration and technology transfers. Professor Jeong is recognized for his pioneering research in protein, antibody, cellular engineering, and protein displays and chips.
2015.10.19
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KAIST's Research Team Receives the Best Paper Award from the IEEE Transaction on Power Electronics
A research team led by Professor Chun T. Rim of the Department of Nuclear and Quantum Engineering at the Korea Advanced Institute of Science and Technology (KAIST) has received the First Prize Papers Award from the IEEE (Institute of Electrical and Electronics Engineers) Transactions on Power Electronics (TPEL), a peer-reviewed journal that covers fundamental technologies used in the control and conversion of electric power. A total of three research papers received this award in 2015. Each year, TPEL’s editors select three best papers among those published in the journal during the preceding calendar year. In 2014, the TPEL published 579 papers. Professor Rim’s paper was picked out as one of the three papers published last year for the First Prize Papers Award. Entitled “Generalized Active EMF (electromagnetic field) Cancel Methods for Wireless Electric Vehicles (http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=6684288&tag=1),” the paper proposed, for the first time in the world, three generalized design methods for cancelling the total EMF generated from wireless electric vehicles. This technology, researchers said, can be applied to any wireless power transfer systems. The award ceremony will be held at the upcoming conference of the 2015 IEEE Energy Conversion Congress and Expo in September in Montreal, Canada.
2015.08.27
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Nature Biotechnology Nominates Sang Yup Lee of KAIST for Top 20 Translational Researchers of 2014
Nature Biotechnology, recognized as the most prestigious journal in the field of biotechnology, has released today its list of the Top 20 Translational Researchers of 2014. Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering at KAIST (Korea Advanced Institute of Science and Technology) ranked seventh in the list. He is the only Asian researcher listed. The journal, in partnership with IP Checkups, a patent analytics firm, presents an annual ranking of researchers based on their paper and patent output. The list includes, among others, each researcher’s most-cited patent in the past five years and their H index, a measurement to evaluate the impact of a researcher’s published work utilizing citation analysis. (More details can be found at http://www.nature.com/bioent/2015/150801/full/bioe.2015.9.html.) American institutions made up the majority of the list, with 18 universities and research institutes, and the remainder was filled by KAIST in Korea and the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia. Globally known as a leading researcher in systems metabolic engineering, Professor Lee has published more than 500 journal papers and 580 patents. He has received many awards, including the Citation Classic Award, Elmer Gaden Award, Merck Metabolic Engineering Award, ACS Marvin Johnson Award, SIMB Charles Thom Award, POSCO TJ Park Prize, Amgen Biochemical Engineering Award, and the Ho Am Prize in Engineering.
2015.08.27
View 8345
Science and Technology Policy Professor Chihyung Jeon Awarded Rachel Carson Fellowship
KAIST Graduate School of Science and Technology Policy Professor Chihyung Jeon has been awarded the Rachel Carson Fellowship 2015-2016. Rachel Carson Center for Environment and Society is a research center for environmental humanities and social sciences, supported by the German Federal Ministry of Education and Research. It was founded by Ludwig-Maximilians-Universität, Munich, Germany and the Deutsches Museum as a joint initiative in 2009. Rachel Carson Center supports researches in humanities and social sciences on the interactions between the environment and the society, following the footsteps of Rachel Cason, who raised awareness on the chemical environmental damage and started global environmental movement through her published book “Silent Spring” in 1962. The center is awarding Rachel Carson Fellowships to established researchers to fund their writing and promote exchange of research. This year, 31 fellowships were awarded. Professor Jeon will conduct research on "A Dredged Nation: The Four Rivers Restoration Project and the Envirotechnical Transformation of South Korea" and will also hold an additional post of International Curatorial Fellow at the Deutsches Museum.
2015.06.11
View 7943
KAIST Develops Ultrathin Polymer Insulators Key to Low-Power Soft Electronics
Using an initiated chemical vapor deposition technique, the research team created an ultrathin polymeric insulating layer essential in realizing transistors with flexibility and low power consumption. This advance is expected to accelerate the commercialization of wearable and soft electronics. A group of researchers at the Korea Advanced Institute of Science and Technology (KAIST) developed a high-performance ultrathin polymeric insulator for field-effect transistors (FETs). The researchers used vaporized monomers to form polymeric films grown conformally on various surfaces including plastics to produce a versatile insulator that meets a wide range of requirements for next-generation electronic devices. Their research results were published online in Nature Materials on March 9th, 2015. FETs are an essential component for any modern electronic device used in our daily life from cell phones and computers, to flat-panel displays. Along with three electrodes (gate, source, and drain), FETs consist of an insulating layer and a semiconductor channel layer. The insulator in FETs plays an important role in controlling the conductance of the semiconductor channel and thus current flow within the translators. For reliable and low-power operation of FETs, electrically robust, ultrathin insulators are essential. Conventionally, such insulators are made of inorganic materials (e.g., oxides and nitrides) built on a hard surface such as silicon or glass due to their excellent insulating performance and reliability. However, these insulators were difficult to implement into soft electronics due to their rigidity and high process temperature. In recent years, many researchers have studied polymers as promising insulating materials that are compatible with soft unconventional substrates and emerging semiconductor materials. The traditional technique employed in developing a polymer insulator, however, had the limitations of low surface coverage at ultra-low thickness, hindering FETs adopting polymeric insulators from operating at low voltage. A KAIST research team led by Professor Sung Gap Im of the Chemical and Biomolecular Engineering Department and Professor Seunghyup Yoo and Professor Byung Jin Cho of the Electrical Engineering Department developed an insulating layer of organic polymers, “pV3D3,” that can be greatly scaled down, without losing its ideal insulating properties, to a thickness of less than 10 nanometers (nm) using the all-dry vapor-phase technique called the “initiated chemical vapor deposition (iCVD).” The iCVD process allows gaseous monomers and initiators to react with each other in a low vacuum condition, and as a result, conformal polymeric films with excellent insulating properties are deposited on a substrate. Unlike the traditional technique, the surface-growing character of iCVD can overcome the problems associated with surface tension and produce highly uniform and pure ultrathin polymeric films over a large area with virtually no surface or substrate limitations. Furthermore, most iCVD polymers are created at room temperature, which lessens the strain exerted upon and damage done to the substrates. With the pV3D3 insulator, the research team built low-power, high-performance FETs based on various semiconductor materials such as organics, graphene, and oxides, demonstrating the pV3D3 insulator’s wide range of material compatibility. They also manufactured a stick-on, removable electronic component using conventional packaging tape as a substrate. In collaboration with Professor Yong-Young Noh from Dongguk University in Korea, the team successfully developed a transistor array on a large-scale flexible substrate with the pV3D3 insulator. Professor Im said, “The down-scalability and wide range of compatibility observed with iCVD-grown pV3D3 are unprecedented for polymeric insulators. Our iCVD pV3D3 polymeric films showed an insulating performance comparable to that of inorganic insulating layers, even when their thickness were scaled down to sub-10 nm. We expect our development will greatly benefit flexible or soft electronics, which will play a key role in the success of emerging electronic devices such as wearable computers.” The title of the research paper is “Synthesis of ultrathin polymer insulating layers by initiated chemical vapor deposition for low-power soft electronics” (Digital Object Identifier (DOI) number is 10.1038/nmat4237). Picture 1: A schematic image to show how the initiated chemical vapor deposition (iCVD) technique produces pV3D3 polymeric films: (i) introduction of vaporized monomers and initiators, (ii) activation of initiators to thermally dissociate into radicals, (iii) adsorption of monomers and initiator radicals onto a substrate, and (iv) transformation of free-radical polymerization into pV3D3 thin films. Picture 2: This is a transistor array fabricated on a large scale, highly flexible substrate with pV3D3 polymeric films. Picture 3: This photograph shows an electronic component fabricated on a conventional packaging tape, which is attachable or detachable, with pV3D3 polymeric films embedded.
2015.03.10
View 12073
KAIST and Petersburg State Transport University Sign a MOU on Green Transportation
The Petersburg State Transport University (PSTU) in Russia is a higher education institution specializing in railway transport. KAIST and PSTU signed a memorandum of understating (MOU) on October 28, 2014 at the KAIST campus and agreed to collaborate in the research of and hold academic exchanges for green transportation. Based on the agreement, the two institutions will collaborate in the development of a high capacity railway that is powered through wireless power transfer technology and will exchange personnel and academic knowledge to advance the field of green transportation. The Graduate School for Green Transportation (GSGT) at KAIST organized a seminar which took place after the MOU signing ceremony. Professor Dong-Ho Cho, the Dean of GSGT, presented a keynote speech at the seminar on “Korea’s Green Transportation Policy and Its Technology Development Status” to the audience including the PSTU delegation. Established in 1809, PSTU is one of the oldest and most prestigious engineering universities in Russia, serving as an important scientific and research center in the area of engineering, construction, and railway operation.
2014.11.04
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KAIST Co-owns the HEVC Patent Portfolio License
MPEG LA, LLC, a firm based in Denver, Colorado, which licenses patent pools covering essential patents required for the use of video coding technology, such as MPEG-2, MPEG-4 Visual (Part 2), and HEVC/H.264, announced the availability of the High Efficiency Video Coding (HEVC) Patent Portfolio License on September 29, 2014. The HEVC standard, also known as H.265 and MPEG-H Part 2, is necessary to improve video coding and transmission efficiency for the Internet, televisions, and mobile gadgets with increased speed and capacity. Through the portfolio license, users can easily obtain patent rights required for the HEVC standard in a single transaction, instead of negotiating separate licenses from multiple patent holders. A total of 23 enterprises currently own essential HEVC patents. KAIST is the only Korean university among the joint patent owners. Collaborating with the Korea Broadcasting System (KBS) and the Electronics and Telecommunications Research Institute (ETRI), Professor Mun-Chul Kim of the Electrical Engineering Department at KAIST developed one of the core patents. For a link to a press release distributed by MPEG LA, LLC, please see: MPEG LA, LLC, September 29, 2014 "MPEG LA, LLC Offers HEVC Patent Portfolio License" http://www.mpegla.com/main/Pages/Media.aspx
2014.10.02
View 11027
President Steve Kang of KAIST Attends the 2014 Summer Davos Forum in Tianjin, China
President Steve Kang of KAIST will attend the 2014 Annual Meeting of the New Champions, the World Economic Forum (WEF), to be held on September 10-12, 2014 in Tianjin, China. KAIST holds its own IdeasLab session on nanotechnology on September 12, 2014. On September 10, 2014, President Steve Kang will participate in a private session hosted by the Global University Leaders Forum (GULF) community at WEF as a panelist. In addition to President Kang, eight presidents from top global universities such as the National University of Singapore, Peking University, ETH Zurich (Swiss Federal Institute of Technology), University of Tokyo, and Carnegie Mellon University will join the panel discussion under the topic, “Increasing the Translational Impact of University Research.” Specifically, the presidents will address issues related to the importance of university-led technology transfer in Asia, key strategies and goals for technology transfer, and implementation approaches taken by each university to promote technology transfer from university to industry. President Kang was invited to this GULF session, the only attendant from Korean universities, in recognition of his long time experience and expertise in education and research. In 2006, WEF created the GULF, a small community of the presidents of top universities in the world, aiming to offer an open platform for high-level dialogues on issues of higher education and research with other sectors, as well as to foster collaboration between universities in areas of significance for global policy. As of 2014, a total of 25 globally leading universities, including Harvard University, University of Cambridge, and Massachusetts Institute of Technology, are GULF members. KAIST, which joined the club this year, is the only Korean university. The 2014 Annual Meeting of the New Champions, also known as the Summer Davos Forum, hosts numerous sessions under the theme of “Creating Value through Innovation.” At the Forum, a total of ten IdeasLab sessions will be hosted. KAIST was invited to run its own IdeasLab on nanotechnology on September 12, 2014. Together with President Kang, Professors Sang Ouk Kim and Keon Jae Lee from the Department of Materials Science Engineering, KAIST, and Professors Sang Yup Lee and Hyunjoo Lee from the Department of Chemical and Biomolecular Engineering, KAIST, will present their own speeches on the topic entitled “From diagnostics to materials, how is nanotechnology changing lives?” President Kang will give the opening speech at the KAIST IdeasLab. He said that an invitation from WEF to join the IdeasLab spoke well for KAIST: “KAIST is the first and the only Korean university ever invited to run its own IdeasLab at the World Economic Forum. The IdeasLab is an expert group meeting, conducted only by the world’s most prestigious universities and research institutes. At the IdeasLab sessions, global leaders from different sectors identify major issues facing higher education and humanity and explore solutions through science and technology innovation. Holding our own IdeasLab on one of our strongest fields, nanotechnology, is indeed an excellent opportunity for KAIST to show its strength in academic and research excellence on the global stage.”
2014.09.08
View 12088
Professor Min Hyuk Kim Appointed an Associate Editor on ACM Transactions on Graphics
Professor Min Hyuk Kim of KAIST's Computer Science Department has been appointed an associate editor for a prestigious international journal in the field of graphics, ACM Transactions on Graphics (TOG). Founded in 1947, the Association for Computing Machinery (ACM) is the world’s largest educational and scientific computing society, delivering knowledge that advances computing as a science and profession. Published during the past 35 years, ACM TOG is a highly regarded, peer-reviewed scientific journal that aims to disseminate the latest findings of research in computer graphics. Professor Kim is the first Korean scholar to serve the journal as an editor. Professor Kim’s responsibilities are many, and they include selecting appropriate reviewers for submitted manuscripts to be published in the journal and reporting the results of review process. He said, “The appointment was a great honor, and I’m looking forward to having the opportunity to make further contributions to the advancement of the graphics field.” Professor Kim has published numerous papers on computer graphics with a focus on research in 3D imaging spectroscopy and visual perception.
2014.07.14
View 8842
Discovery Channel Featured "TransWall" Developed by Professor Woohun Lee
One of the most popular television programs at Discovery Channel in Canada, Daily Planet, a daily science magazine show that delivers a fascinating mix of documentaries and features, aired "TransWall” (http://vimeo.com/70391422) developed by Professor Woohun Lee of Industrial Design at KAIST. TransWall is a two-sided touchable transparent display with a surface transducer incorporated in the display. It enables users to see, hear, or even touch people standing on the other side of the display, thereby enhancing interactive experiences when playing games or communicating. TransWall was introduced at the 2014 ACM (Association for Computing Machinery) Conference on Human Factors in Computing Systems (CHI) held in Toronto, Canada, from April 26 to May 1. The Channel learned about the technology at the conference and produced the show on April 30, 2014. To watch the show, please visit: http://www.youtube.com/watch?v=5GGP59S7T2k&list=PLXmuftxI6pTXuyjjrGFlcN5YFTKZinDhK.
2014.05.29
View 8529
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