Kaist

Improved Efficiency and Stability of CQD Solar Cel..

(from left: Professor Jung-Yong Lee and Dr. Se-Woong Baek)   Recently, the power conversion efficiency (PCE) of colloidal quantum dot (CQD)-based solar cells has been enhanced, paving the way for their commercialization in various fields; nevertheless, they are still a long way from being commercialized due to their efficiency not matching their stability. In this research, a KAIST team achieved highly stable and efficient CQD-based solar cells by using an amorphous organic layer to block oxygen and water permeation.   CQD-based solar cells are light-weight, flexible, and they boost light harvesting by absorbing near-infrared lights. Especially, they draw special attention for their optical properties controlled efficiently by changing the quantum dot sizes. However, they are still incompatible with existing solar cells in terms of efficiency, stability, and cost. Therefore, there is great demand for a novel technology that can simultaneously improve both PCE and stability while using an inexpensive electrode material.   Responding to this demand, Professor Jung-Yong Lee from the Graduate School of Energy, Environment, Water and Sustainability and his team introduced a technology to improve the efficiency and stability of CQD-based solar cells.   The team found that an amorphous organic thin film has a strong resistance to oxygen and water. Using these properties, they employed this doped organic layer as a top-hole selective layer (HSL) for the PbS CQD solar cells, and confirmed that the hydro/oxo-phobic properties of the layer efficiently protected the PbS layer. According to the molecular dynamics simulations, the layer significantly postponed the oxygen and water permeation into the PbS layer. Moreover, the efficient injection of the holes in the layer reduced interfacial resistance and improved performance.   With this technology, the team finally developed CQD-based solar cells with excellent stability. The PCE of their device stood at 11.7％ and maintained over 90％ of its initial performance when stored for one year under ambient conditions.    Professor Lee said, “This technology can be also applied to QD LEDs and Perovskite devices. I hope this technology can hasten the commercialization of CQD-based solar cells.”   This research, led by Dr. Se-Woong Baek and a Ph.D. student, Sang-Hoon Lee, was published in Energy & Environmental Science on May 10.    Figure 1. The schematic of the equilibrated structure of the amorphous organic film   Figure 2. Schematic illustration of CQD-based solar cells and graphs showing their performance

KAIST Reveals Mathematical Principle behind AI’s ‘..

(from left: Professor Jong Chul Ye, PhD candidates Yoseob Han and Eunju Cha)   A KAIST research team identified the geometrical structure of artificial intelligence (AI) and discovered the mathematical principles of highly performing artificial neural networks, which can be applicable in fields such as medical imaging.    Deep neural networks are an exemplary method of implementing deep learning, which is at the core of the AI technology, and have shown explosive growth in recent years. This technique has been used in various fields, such as image and speech recognition as well as image processing.    Despite its excellent performance and usefulness, the exact working principles of deep neural networks has not been well understood, and they often suffer from unexpected results or errors. Hence, there is an increasing social and technical demand for interpretable deep neural network models.   To address these issues, Professor Jong Chul Ye from the Department of Bio & Brain Engineering and his team attempted to find the geometric structure in a higher dimensional space where the structure of the deep neural network can be easily understood. They proposed a general deep learning framework, called deep convolutional framelets, to understand the mathematical principle of a deep neural network in terms of the mathematical tools in Harmonic analysis.    As a result, it was found that deep neural networks’ structure appears during the process of decomposition of high dimensionally lifted signal via Hankel matrix, which is a high-dimensional structure formerly studied intensively in the field of signal processing.   In the process of decomposing the lifted signal, two bases categorized as local and non-local basis emerge. The researchers found that non-local and local basis functions play a role in pooling and filtering operation in convolutional neural network, respectively.    Previously, when implementing AI, deep neural networks were usually constructed through empirical trial and errors. The significance of the research lies in the fact that it provides a mathematical understanding on the neural network structure in high dimensional space, which guides users to design an optimized neural network.   They demonstrated improved performance of the deep convolutional framelets’ neural networks in the applications of image denoising, image pixel in painting, and medical image restoration.     Professor Ye said, “Unlike conventional neural networks designed through trial-and-error, our theory shows that neural network structure can be optimized to each desired application and are easily predictable in their effects by exploiting the high dimensional geometry. This technology can be applied to a variety of fields requiring interpretation of the architecture, such as medical imaging.”   This research, led by PhD candidates Yoseob Han and Eunju Cha, was published in the April 26th issue of the SIAM Journal on Imaging Sciences.    Figure 1. The design of deep neural network using mathematical principles   Figure 2. The results of image noise cancelling   Figure 3. The artificial neural network restoration results in the case where 80％ of the pixels are lost

Professor Emeritus Jung Ki Park Won the IBA Techno..

(Professor Emeritus Jung Ki Park) Professor Emeritus Jung Ki Park from the Department of Chemical and Biomolecular Engineering received the IBA Technology Award from the International Battery Association (IBA).   IBA 2018 was held from March 11 to 16 on Jeju Island, which was the first time it was hosted in Korea. The conference was an excellent opportunity to let the world know the level of the Korean rechargeable battery industry and its technology.    Professor Park delivered his keynote speech titled Advances in Lithium Batteries in Korea at the conference and received the IBA Technology Award as the first Korean recipient.   ?Professor Park is a world-renowned scholar who was a groundbreaker in the rechargeable battery industry. He was recognized by the IBA Award Committee for his contributions carrying out research and development, fostering competent people, and enhancing the lithium rechargeable battery industry in Korea over the last 30 years.    Professor Park said, “It is my great honor to receive this award, which is the best international award in the field of rechargeable batteries. I would like to share this with my colleagues and students. As competition in the rechargeable industry intensifies, systemic cooperation among industries, academia, and government is needed for the continued development of the battery industry in Korea.

Recognizing Seven Different Face Emotions on a Mob..

(Professor Hoi-Jun Yoo)   A KAIST research team succeeded in achieving face emotion recognition on a mobile platform by developing an AI semiconductor IC that processes two neural networks on a single chip.   Professor Hoi-Jun Yoo and his team (Primary researcher: Jinmook Lee Ph. D. student) from the School of Electrical Engineering developed a unified deep neural network processing unit (UNPU).    Deep learning is a technology for machine learning based on artificial neural networks, which allows a computer to learn by itself, just like a human.   The developed chip adjusts the weight precision (from 1 bit to 16 bit) of a neural network inside of the semiconductor in order to optimize energy efficiency and accuracy. With a single chip, it can process a convolutional neural network (CNN) and recurrent neural network (RNN) simultaneously. CNN is used for categorizing and recognizing images while RNN is for action recognition and speech recognition, such as time-series information.    Moreover, it enables an adjustment in energy efficiency and accuracy dynamically while recognizing objects. To realize mobile AI technology, it needs to process high-speed operations with low energy, otherwise the battery can run out quickly due to processing massive amounts of information at once. According to the team, this chip has better operation performance compared to world-class level mobile AI chips such as Google TPU. The energy efficiency of the new chip is 4 times higher than the TPU.   In order to demonstrate its high performance, the team installed UNPU in a smartphone to facilitate automatic face emotion recognition on the smartphone. This system displays a user’s emotions in real time. The research results for this system were presented at the 2018 International Solid-State Circuits Conference (ISSCC) in San Francisco on February 13.   Professor Yoo said, “We have developed a semiconductor that accelerates with low power requirements in order to realize AI on mobile platforms. We are hoping that this technology will be applied in various areas, such as object recognition, emotion recognition, action recognition, and automatic translation. Within one year, we will commercialize this technology.”

KAIST, First to Win the Cube Satellite Competition

?Professor Hyochoong Bang from the Department of Aerospace Engineering and his team received the Minister of Science and ICT Award at the 1st Cube Satellite Competition.   The team actually participated in the competition in 2012, but it took several years for the awarding ceremony since it took years for the satellites to be designed, produced, and launched.   The KAIST team successfully developed a cube satellite, named ‘Little Intelligent Nanosatellite of KAIST (LINK)’ and completed its launch in April 2017.   LINK (size: 20cmx10cmx10cm, weight: 2kg) mounted mass spectrometry and Langmuir probe for Earth observation. The Langmuir probe was developed by Professor Kyoung Wook Min from the Department of Physics, KAIST.   Yeerang Lim, a PhD student from the Department of Aerospace Engineering said, “I still remember the feeling that I had on the day when LINK launched into orbit and sent back signals. I hope that space exploration is not something far away but attainable for us in near future.”

Professor Jungwon Kim Wins the 8th Haerim Optics a..

(Professor Jungwon Kim)   Professor Jungwon Kim from the Department of Mechanical Engineering received the 8th Haerim Optics and Photonics Award from the Optical Society of Korea (OSK).   He was recognized for his dedication to pioneering the field of microwave photonics by developing ultra-low noise fiber photonics lasers.   The Haerim Optics and Photonics Award is given to an outstanding researcher who has made academic contributions in the field of optics and photonics for the last five years.   The name of the award (Haerim) comes from the pen-name of the renowned scholar, Professor Un-Chul Paek, because it is maintained using funds he contributed to the OSK.   The OSK will confer the award on February 8 during the 29th OSK Annual Meeting and Winter Conference of 2018.

Three Professors Named KAST Fellows

 (Professor Dan Keun Sung at the center) (Professor Y.H. Cho at the center) (Professor K.H. Cho at the center)    The Korean Academy of Science and Technology (KAST) inducted three KAIST professors as fellows at the New Year’s ceremony held at KAST on January 12. They were among the 24 newly elected fellows of the most distinguished academy in Korea. The new fellows are Professor Dan Keun Sung of the School of Electrical Engineering, Professor Kwang-Hyun Cho of the Department of Bio and Brain Engineering, and Professor Yong-Hoon Cho of the Department of Physics. Professor Sung was recognized for his lifetime academic achievements in fields related with network protocols and energy ICT. He also played a crucial role in launching the Korean satellites KITSAT-1,2,3 and the establishment of the Satellite Technology Research Center at KAIST. Professor Y.H.Cho has been a pioneer in the field of low-dimensional semiconductor-powered quantum photonics that enables quantum optical research in solid state. He has been recognized as a renowned scholar in this field internationally. Professor K.H.Cho has conducted original research that combines IT and BT in systems biology and has applied novel technologies of electronic modeling and computer simulation analysis for investigating complex life sciences. Professor Cho, who is in his 40s, is the youngest fellow among the newly inducted fellows.

Professor Jung Awarded the Pople Medal by the APAT..

   (Professor Yousung Jung)     Professor Yousung Jung of the Graduate School of EEWS won the Pople Medal from the Asia-Pacific Association of Theoretical & Computational Chemists (APATCC).   The Pople Medal has been awarded annually since 2007 to recognize young scholars in the fields of theoretical/computational chemistry in honor of Sir John Anthony Pople, who passed away in 2004. Dr. Pople was a British theoretical chemist and a Nobel laureate in 1998 for his development of computational methods in quantum chemistry.   The Pople Medal is awarded to scientists at or under the age of 45 in the Asia-Pacific region who have distinguished themselves through pioneering and important contributions.   Professor Jung was honored for his outstanding contributions to developing efficient electronic structure methods and their applications to energy materials discovery. He has published more than 120 papers in prestigious academic journals. He also has an h-index of 44, and has been cited more than 8,000 times.

Distinguished Professor Sang Yup Lee Named NAI Fel..

(Distinguished Professor Sang Yup Lee)     Distinguished Professor Sang Yup Lee of the Department of Chemical and Biomolecular Engineering was named to the National Academy of Inventors in the US. He is the first Korean scholar ever elected as a NAI fellow. The NAI is a non-profit member organization with over 4,000 individual inventors and fellows spanning more than 250 institutions worldwide. It is comprised of universities as well as governmental and non-profit research institutes. The academy was founded in 2010 to recognize and encourage inventors with patents from the US Patent and Trademark Office. So far, 575 fellows from 229 institutions have been elected. The academy said Professor Lee has been recognized for fellowship induction as he has demonstrated a highly prolific spirit of innovation in creating or facilitating outstanding inventions that have made a tangible impact on quality of life, economic development, and the welfare of society. Distinguished Professor Lee, a pioneering researcher and scholar in the field of systems metabolic engineering, was ranked in the top 1％ of highly cited researchers (HCR) this year. Over the past 11 years, he published more than 130,000 articles in prestigious journals around the world. He has been cited more than 34,000 times since he started working at KAIST in 1994. He is also the first Korean ever elected to both the National Academy of Sciences (NAS) and the National Academy of Engineering (NAE) in the US, becoming the one of 13 foreign scholars in the world holding two prestigious institutions’ fellowships. Dr. Lee is currently the dean of KAIST Institutes, the world-leading institute for multi and interdisciplinary research. He is also serving as co-chair of the Global Council on Biotechnology and is a member of the Global Future Council on the Fourth Industrial Revolution at the World Economic Forum.

Professor Dong Ho Cho, Awarded at the 13th Haedong..

    Professor Dong Ho Cho of the School of Electrical Engineering at KAIST received an award at the 13th Haedong Conference 2017 in Seoul on the first of December. The Korean Institute of Communications and Information Sciences recognized Professor Cho for his significant contributions in the field of mobile communication networks. He has carried out groundbreaking research on mobile systems, including architecture, protocols, algorithms, optimization, and efficiency analysis. As a result, he has produced 73 papers in renowned international journals, 138 papers at international conferences, and filed 52 international patents and 121 domestic patents. In addition, he transferred 14 of the patents he filed to Korean and international companies.