New Nanoparticle Drug Combination For Atherosclero..
< Professor Ji-Ho Park (left) and Dr. Heegon Kim (right) > Physicochemical cargo-switching nanoparticles (CSNP) designed by KAIST can help significantly reduce cholesterol and macrophage foam cells in arteries, which are the two main triggers for atherosclerotic plaque and inflammation. The CSNP-based combination drug delivery therapy was proved to exert cholesterol-lowering, anti-inflammatory, and anti-proliferative functions of two common medications for treating and preventing atherosclerosis that are cyclodextrin and statin. Professor Ji-Ho Park and Dr. Heegon Kim from KAIST’s Department of Bio and Brain Engineering said their study has shown great potential for future applications with reduced side effects. Atherosclerosis is a chronic inflammatory vascular disease that is characterized by the accumulation of cholesterol and cholesterol-loaded macrophage foam cells in the intima. When this atherosclerotic plaque clogs and narrows the artery walls, they restrict blood flow and cause various cardiovascular conditions such as heart attacks and strokes. Heart attacks and strokes are the world’s first and fifth causes of death respectively. Oral statin administration has been used in clinics as a standard care for atherosclerosis, which is prescribed to lower blood cholesterol and inhibit its accumulation within the plaque. Although statins can effectively prevent the progression of plaque growth, they have only shown modest efficacy in eliminating the already-established plaque. Therefore, patients are required to take statin drugs for the rest of their lives and will always carry the risk of plaque ruptures that can trigger a blood clot. To address these issues, Professor Park and Dr. Kim exploited another antiatherogenic agent called cyclodextrin. In their paper published in the Journal of Controlled Release on March 10, Professor Park and Dr. Kim reported that the polymeric formulation of cyclodextrin with a diameter of approximately 10 nanometers(nm) can accumulate within the atherosclerotic plaque 14 times more and effectively reduce the plaque even at lower doses, compared to cyclodextrin in a non-polymer structure. Moreover, although cyclodextrin is known to have a cytotoxic effect on hair cells in the cochlea, which can lead to hearing loss, cyclodextrin polymers developed by Professor Park’s research group exhibited a varying biodistribution profile and did not have this side effect. In the follow-up study reported in ACS Nano on April 28, the researchers exploited both cyclodextrin and statin and form the cyclodextrin-statin self-assembly drug complex, based on previous findings that each drug can exert local anti-atherosclerosis effect within the plaque. The complex formation processes were optimized to obtain homogeneous and stable nanoparticles with a diameter of about 100 nm for systematic injection. The therapeutic synergy of cyclodextrin and statin could reportedly enhance plaque-targeted drug delivery and anti-inflammation. Cyclodextrin led to the regression of cholesterol in the established plaque, and the statins were shown to inhibit the proliferation of macrophage foam cells. The study suggested that combination therapy is required to resolve the complex inflammatory cholesterol-rich microenvironment within the plaque. Professor Park said, “While nanomedicine has been mainly developed for the treatment of cancers, our studies show that nanomedicine can also play a significant role in treating and preventing atherosclerosis, which causes various cardiovascular diseases that are the leading causes of death worldwide.” This work was supported by KAIST and the National Research Foundation (NRF) of Korea. < Figure. Antiatherogenic effect of CSNP. > Publications: 1. Heegon Kim, Junhee Han, and Ji-Ho Park. (2020) ‘Cyclodextrin polymer improves atherosclerosis therapy and reduces ototoxicity’ Journal of Controlled Release. Volume 319. Page 77-86. Available online at https://doi.org/10.1016/j.jconrel.2019.12.021 2. Kim, H., et al. (2020) ‘Affinity-Driven Design of Cargo-Switching Nanoparticles to Leverage a Cholesterol-Rich Microenvironment for Atherosclerosis Therapy’ ACS Nano. Available online at https://doi.org/10.1021/acsnano.9b08216 Profile: Ji-Ho Park, Ph.D. Associate Professor jihopark＠kaist.ac.kr http://openwetware.org/wiki/Park_Lab Biomaterials Engineering Laboratory (BEL) Department of Bio and Brain Engineering (BIOENG) Korea Advanced Institute of Science and Technology (KAIST) https://www.kaist.ac.kr Daejeon 34141, Korea Profile: Heegon Kim, Ph.D. Postdoctoral Researcher heegon＠kaist.ac.kr BEL, BIOENG, KAIST (END)
Professor Dongsu Han Named Program Chair for ACM C..
< Professor Dongsu Han > Professor Dongsu Han from the School of Electrical Engineering has been appointed as the program chair for the 16th Association for Computing Machinery’s International Conference on emerging Networking EXperiments and Technologies (ACM CoNEXT 2020). Professor Han is the first program chair to be appointed from an Asian institution. ACM CoNEXT is hosted by ACM SIGCOMM, ACM's Special Interest Group on Data Communications, which specializes in the field of communication and computer networks. Professor Han will serve as program co-chair along with Professor Anja Feldmann from the Max Planck Institute for Informatics. Together, they have appointed 40 world-leading researchers as program committee members for this conference, including Professor Song Min Kim from KAIST School of Electrical Engineering. Paper submissions for the conference can be made by the end of June, and the event itself is to take place from the 1st to 4th of December. Conference Website: https://conferences2.sigcomm.org/co-next/2020/#！/home (END)
Professor Youngchul Kim Joins Presidential Commiss..
< Professor Youngchul Kim > Professor Youngchul Kim from the Department of Civil and Environmental Engineering, who is also the Director of the Smart City Research Center at KAIST, was appointed as a commissioner of the 6th Presidential Commission on Architecture Policy on May 19. Professor Kim will contribute to coordinating and deliberating national architecture and urban development policies. He will serve a two-year term beginning this month. The Presidential Commission on Architecture Policy is made up of 30 commissioners. Nineteen members, including Professor Kim, are experts from the private sector, and the rest include the Minister of Land, Infrastructure, and Transport, the Minister for Environment, and other government officials. The non-governmental commissioners represent a diverse mixture of genders, ages, and regions for the balanced development of the nation. (END)
A Deep-Learned E-Skin Decodes Complex Human Motion
A deep-learning powered single-strained electronic skin sensor can capture human motion from a distance. The single strain sensor placed on the wrist decodes complex five-finger motions in real time with a virtual 3D hand that mirrors the original motions. The deep neural network boosted by rapid situation learning (RSL) ensures stable operation regardless of its position on the surface of the skin. Conventional approaches require many sensor networks that cover the entire curvilinear surfaces of the target area. Unlike conventional wafer-based fabrication, this laser fabrication provides a new sensing paradigm for motion tracking. The research team, led by Professor Sungho Jo from the School of Computing, collaborated with Professor Seunghwan Ko from Seoul National University to design this new measuring system that extracts signals corresponding to multiple finger motions by generating cracks in metal nanoparticle films using laser technology. The sensor patch was then attached to a user’s wrist to detect the movement of the fingers. The concept of this research started from the idea that pinpointing a single area would be more efficient for identifying movements than affixing sensors to every joint and muscle. To make this targeting strategy work, it needs to accurately capture the signals from different areas at the point where they all converge, and then decoupling the information entangled in the converged signals. To maximize users’ usability and mobility, the research team used a single-channeled sensor to generate the signals corresponding to complex hand motions. The rapid situation learning (RSL) system collects data from arbitrary parts on the wrist and automatically trains the model in a real-time demonstration with a virtual 3D hand that mirrors the original motions. To enhance the sensitivity of the sensor, researchers used laser-induced nanoscale cracking. This sensory system can track the motion of the entire body with a small sensory network and facilitate the indirect remote measurement of human motions, which is applicable for wearable VR/AR systems. The research team said they focused on two tasks while developing the sensor. First, they analyzed the sensor signal patterns into a latent space encapsulating temporal sensor behavior and then they mapped the latent vectors to finger motion metric spaces. Professor Jo said, “Our system is expandable to other body parts. We already confirmed that the sensor is also capable of extracting gait motions from a pelvis. This technology is expected to provide a turning point in health-monitoring, motion tracking, and soft robotics.” This study was featured in Nature Communications. < Figure 1: Deep Learned Sensor collecting epicentral motion > < Figure 2: RSL system based on transfer learning > Publication: Kim, K.K., Ha, I., Kim, M. et al. A deep-learned skin sensor decoding the epicentral human motions. Nature Communications 11, 2149 (2020). https://doi.org/10.1038/s41467-020-16040-y29 Link to download the full-text paper: https://www.nature.com/articles/s41467-020-16040-y.pdf Profile: Professor Sungho Jo Neuro-Machine Augmented Intelligence Lab http://nmail.kaist.ac.kr School of Computing College of Engineering KAIST
Visualization of Functional Components to Characte..
< Dr. Hongjun Kim (left) and Professor Seungbum Hong (right) > Researchers have developed a visualization method that will determine the distribution of components in battery electrodes using atomic force microscopy. The method provides insights into the optimal conditions of composite electrodes and takes us one step closer to being able to manufacture next-generation all-solid-state batteries. Lithium-ion batteries are widely used in smart devices and vehicles. However, their flammability makes them a safety concern, arising from potential leakage of liquid electrolytes. All-solid-state lithium ion batteries have emerged as an alternative because of their better safety and wider electrochemical stability. Despite their advantages, all-solid-state lithium ion batteries still have drawbacks such as limited ion conductivity, insufficient contact areas, and high interfacial resistance between the electrode and solid electrolyte. To solve these issues, studies have been conducted on composite electrodes in which lithium ion conducting additives are dispersed as a medium to provide ion conductive paths at the interface and increase the overall ionic conductivity. It is very important to identify the shape and distribution of the components used in active materials, ion conductors, binders, and conductive additives on a microscopic scale for significantly improving the battery operation performance. The developed method is able to distinguish regions of each component based on detected signal sensitivity, by using various modes of atomic force microscopy on a multiscale basis, including electrochemical strain microscopy and lateral force microscopy. For this research project, both conventional electrodes and composite electrodes were tested, and the results were compared. Individual regions were distinguished and nanoscale correlation between ion reactivity distribution and friction force distribution within a single region was determined to examine the effect of the distribution of binder on the electrochemical strain. The research team explored the electrochemical strain microscopy amplitude/phase and lateral force microscopy friction force dependence on the AC drive voltage and the tip loading force, and used their sensitivities as markers for each component in the composite anode. This method allows for direct multiscale observation of the composite electrode in ambient condition, distinguishing various components and measuring their properties simultaneously. Lead author Dr. Hongjun Kim said, “It is easy to prepare the test sample for observation while providing much higher spatial resolution and intensity resolution for detected signals.” He added, “The method also has the advantage of providing 3D surface morphology information for the observed specimens.” Professor Seungbum Hong from the Department of Material Sciences and Engineering said, “This analytical technique using atomic force microscopy will be useful for quantitatively understanding what role each component of a composite material plays in the final properties.” “Our method not only will suggest the new direction for next-generation all-solid-state battery design on a multiscale basis but also lay the groundwork for innovation in the manufacturing process of other electrochemical materials.” This study is published in ACS Applied Energy Materials and supported by the Big Science Research and Development Project under the Ministry of Science and ICT and the National Research Foundation of Korea, the Basic Research Project under the Wearable Platform Materials Technology Center, and KAIST Global Singularity Research Program for 2019 and 2020. < Figure. AFM images of (a, c) samples A and (b, d) B. (a, b) Topographic height images and (c, d) friction force images, respectively. All images were acquired with a tip loading force of 400 nN. Red lines are guides for the eye. > Profile: Seungbum Hong Professor seungbum＠kaist.ac.kr http://mii.kaist.ac.kr/ Materials Imaging and Integration Laboratory Department of Material Sciences and Engineering KAIST
Hubo Debuts as a News Anchor
< HUBO anchored the evening news on a local TA station TJB on May 14. > HUBO, a humanoid robot developed by Professor Jun-Ho Oh’s team, made its debut as a co-anchor during the TJB prime time news 8 on May 14. “Un-contact" became the new normal after Covid-19 and many business solutions are being transformed using robotics. HUBO made two news reports on contactless services using robots in medical, manufacturing, and logistics industries. HUBO 2, the second generation of HUBO, appeared as a special anchor on the local broadcasting network’s special program in celebration of its 25th anniversary. HUBO is the champion of the 2016 DARPA Robotics Challenge held in the USA. Its FX-2 riding robot also participated in the Olympic torch relay during the 2018 PyeongChang Winter Olympics.
From Dark to Light in a Flash： Smart Film Lets Win..
< (Clockwise from back left) Professor Jung-Wuk Hong, Professor Seokwoo Jeon, Dr. Sang-Eon Lee, and PhD Candidate Donghwi Cho > Researchers have developed a new easy-to-use smart optical film technology that allows smart window devices to autonomously switch between transparent and opaque states in response to the surrounding light conditions. The proposed 3D hybrid nanocomposite film with a highly periodic network structure has empirically demonstrated its high speed and performance, enabling the smart window to quantify and self-regulate its high-contrast optical transmittance. As a proof of concept, a mobile-app-enabled smart window device for Internet of Things (IoT) applications has been realized using the proposed smart optical film with successful expansion to the 3-by-3-inch scale. This energy-efficient and cost-effective technology holds great promise for future use in various applications that require active optical transmission modulation. Flexible optical transmission modulation technologies for smart applications including privacy-protection windows, zero-energy buildings, and beam projection screens have been in the spotlight in recent years. Conventional technologies that used external stimuli such as electricity, heat, or light to modulate optical transmission had only limited applications due to their slow response speeds, unnecessary color switching, and low durability, stability, and safety. The optical transmission modulation contrast achieved by controlling the light scattering interfaces on non-periodic 2D surface structures that often have low optical density such as cracks, wrinkles, and pillars is also generally low. In addition, since the light scattering interfaces are exposed and not subject to any passivation, they can be vulnerable to external damage and may lose optical transmission modulation functions. Furthermore, in-plane scattering interfaces that randomly exist on the surface make large-area modulation with uniformity difficult. Inspired by these limitations, a KAIST research team led by Professor Seokwoo Jeon from the Department of Materials Science and Engineering and Professor Jung-Wuk Hong of the Civil and Environmental Engineering Department used proximity-field nanopatterning (PnP) technology that effectively produces highly periodic 3D hybrid nanostructures, and an atomic layer deposition (ALD) technique that allows the precise control of oxide deposition and the high-quality fabrication of semiconductor devices. The team then successfully produced a large-scale smart optical film with a size of 3 by 3 inches in which ultrathin alumina nanoshells are inserted between the elastomers in a periodic 3D nanonetwork. This “mechano-responsive” 3D hybrid nanocomposite film with a highly periodic network structure is the largest smart optical transmission modulation film that exists. The film has been shown to have state-of-the-art optical transmission modulation of up to 74％ at visible wavelengths from 90％ initial transmission to 16％ in the scattering state under strain. Its durability and stability were proved by more than 10,000 tests of harsh mechanical deformation including stretching, releasing, bending, and being placed under high temperatures of up to 70°C. When this film was used, the transmittance of the smart window device was adjusted promptly and automatically within one second in response to the surrounding light conditions. Through these experiments, the underlying physics of optical scattering phenomena occurring in the heterogeneous interfaces were identified. Their findings were reported in the online edition of Advanced Science on April 26. KAIST Professor Jong-Hwa Shin’s group and Professor Young-Seok Shim at Silla University also collaborated on this project. Donghwi Cho, a PhD candidate in materials science and engineering at KAIST and co-lead author of the study, said, “Our smart optical film technology can better control high-contrast optical transmittance by relatively simple operating principles and with low energy consumption and costs.” “When this technology is applied by simply attaching the film to a conventional smart window glass surface without replacing the existing window system, fast switching and uniform tinting are possible while also securing durability, stability, and safety. In addition, its wide range of applications for stretchable or rollable devices such as wall-type displays for a beam projection screen will also fulfill aesthetic needs,” he added. This work was supported by the National Research Foundation of Korea (NRF), and the Korean Ministries of Science, ICT and Future Planning (MSIP), and Science and ICT (MSIT). < Figure 1. Design concept of and fabrication procedures for the 3D scatterer > < Figure 2. Mechanical and optical simulations of the 3D scatterer > < Figure 3. Demonstrations of the internet of things (IoT) applications: a self-regulating mechano-responsive smart window (MSW) device and a beam projection screen > Publication: Cho, D, et al. (2020) ‘High-Contrast Optical Modulation from Strain-Indicated Nanogaps at 3D Heterogeneous Interfaces’ Advanced Science, 1903708. Available online at https://doi.org/10.1002/advs.201903708 Profile: Seokwoo Jeon, PhD Professor jeon39＠kaist.ac.kr https://fdml.kaist.ac.kr/ Flexible Device and Metamaterials Lab (FDML) Department of Materials Science and Engineering (MSE) Korea Advanced Institute of Science and Technology (KAIST) https://www.kaist.ac.kr Daejeon 34141, Korea Profile: Jung-Wuk Hong, PhD Associate Professor j.hong＠kaist.ac.kr http://aaml.kaist.ac.kr Advanced Applied Mechanics Laboratory (AAML) Department of Civil and Environmental Engineering KAIST Profile: Donghwi Cho PhD Candidate roy0202＠kaist.ac.kr FDML, MSE, KAIST Profile: Young-Seok Shim, PhD Assistant Professor ysshim＠silla.ac.kr Division of Materials Science and Engineering Silla University https://www.silla.ac.kr Busan 46958, Korea (END)
Dr. Dong-Hyun Cho at KARI Receives the 16th Jeong ..
< From left: PhD candidate Yongtae Yun at KAIST, Dr. Dong-Hyun Cho at KARI, Seonju Yim at Kongju National University High School, and MS-PhD candidate Haun-Min Lee at Korea University > Dr. Dong-Hyun Cho, a senior researcher at the Korea Aerospace Research Institute (KARI), was honored as the recipient of the 16th Jeong Hun Cho Award. The award recognizes young scientists in the field of aerospace engineering. Dr. Cho earned his MS and PhD degrees from the KAIST Department of Aerospace Engineering in 2012, and served as a researcher at the Satellite Technology Research Center (SaTReC) at KAIST, before joining the Future Convergence Research Division at KARI. He won this year’s award and received 25 million KRW in prize money. Jeong Hun Cho, who was a PhD candidate in the Department of Aerospace Engineering at KAIST, passed away in a tragic lab accident in May 2003 and was awarded an honorary doctorate posthumously. His family endowed the award and scholarship in his memory. Since 2005, the scholarship has selected three young scholars every year who specialize in aerospace engineering from Cho’s alma maters of KAIST, Korea University, and Kongju National University High School. Dr. Dong-Hyun Cho was selected as this year’s awardee in recognition of his studies on the development and operation of KARISMA, a comprehensive software package for space debris collision risk management. Dr. Cho built a terrestrial testbed and produced a model for the development of a space debris elimination algorithm. He published six papers in SCI-level journals and wrote 35 symposium papers in the field of space development. He also applied or registered approximately 40 patents both in Korea and internationally. The Award Committee also selected three students as scholarship recipients: PhD candidate Yongtae Yun from the Department of Aerospace Engineering at KAIST received 4 million KRW, MS-PhD candidate Haun-Min Lee from the School of Mechanical Engineering at Korea University received 4 million KRW, and Seonju Yim from Kongju National University High School received 3 million KRW. (END)
Professor Tek-jin Nam Elected to DSR Int’l Advisor..
< Professor Tek-jin Nam > Professor Tek-jin Nam from the Department of Industrial Design was elected to serve on the first International Advisory Council (IAC) of the Design Research Society (DRS). The DRS, an academic society in the field of design research, was founded in the UK in 1966 with the mission of developing and promoting design research. The IAC is newly established under the new DRS governance structure, and its members are selected from distinguished design researchers recommended by DRS members around the globe. The new IAC members will carry out various activities offered by the DRS, which include innovating design research, strengthening the design researchers’ network and developing policies to nurture new researchers.
Professor Sukyung Park Named Presidential Science ..
< Professor Sukyung Park > Professor Sukyung Park from the Department of Mechanical Engineering was appointed as the science and technology adviser to the President Jae-in Moon on May 4. Professor Park, at the age of 47, became the youngest member of the president’s senior aide team at Chong Wa Dae. A Chong Wa Dae spokesman said on May 4 while announcing the appointment, “Professor Park, a talent with a great deal of policymaking participation in science and technology, will contribute to accelerating the government’s push for science and technology innovation, especially in the information and communications technology (ICT) sector.” Professor Park joined KAIST in 2004 as the first female professor of mechanical engineering. She is a biomechanics expert who has conducted extensive research on biometric mechanical behaviors. Professor Park is also a member of the KAIST Board of Trustees. Before that, she served as a senior researcher at the Korea Institute of Machinery and Materials (KIMM) as well as a member of the Presidential Advisory Council on Science and Technology. After graduating from Seoul Science High School as the first ever two-year graduate, Professor Park earned a bachelor and master’s degrees in mechanical engineering at KAIST. She then finished her Ph.D. from the University of Michigan. (END)
Researchers Present a Microbial Strain Capable of ..
< From left:Ph.D.candidate Gi Bae Kim, Dr.Jung Ho Ahn, Ph.D.candiate Jong An Lee, and Distinguished Professor Sang Yup Lee > A research team led by Distinguished Professor Sang Yup Lee reported the production of a microbial strain capable of the massive production of succinic acid with the highest production efficiency to date. This strategy of integrating systems metabolic engineering with enzyme engineering will be useful for the production of industrially competitive bio-based chemicals. Their strategy was described in Nature Communications on April 23. The bio-based production of industrial chemicals from renewable non-food biomass has become increasingly important as a sustainable substitute for conventional petroleum-based production processes relying on fossil resources. Here, systems metabolic engineering, which is the key component for biorefinery technology, is utilized to effectively engineer the complex metabolic pathways of microorganisms to enable the efficient production of industrial chemicals. Succinic acid, a four-carbon dicarboxylic acid, is one of the most promising platform chemicals serving as a precursor for industrially important chemicals. Among microorganisms producing succinic acid, Mannheimia succiniciproducens has been proven to be one of the best strains for succinic acid production. The research team has developed a bio-based succinic acid production technology using the M. succiniciproducens strain isolated from the rumen of Korean cow for over 20 years and succeeded in developing a strain capable of producing succinic acid with the highest production efficiency. They carried out systems metabolic engineering to optimize the succinic acid production pathway of the M. succiniciproducens strain by determining the crystal structure of key enzymes important for succinic acid production and performing protein engineering to develop enzymes with better catalytic performance. As a result, 134 g per liter of succinic acid was produced from the fermentation of an engineered strain using glucose, glycerol, and carbon dioxide. They were able to achieve 21 g per liter per hour of succinic acid production, which is one of the key factors determining the economic feasibility of the overall production process. This is the world’s best succinic acid production efficiency reported to date. Previous production methods averaged 1~3 g per liter per hour. Distinguished professor Sang Yup Lee explained that his team’s work will significantly contribute to transforming the current petrochemical-based industry into an eco-friendly bio-based one. “Our research on the highly efficient bio-based production of succinic acid from renewable non-food resources and carbon dioxide has provided a basis for reducing our strong dependence on fossil resources, which is the main cause of the environmental crisis,” Professor Lee said. This work was supported by the Technology Development Program to Solve Climate Changes via Systems Metabolic Engineering for Biorefineries and the C1 Gas Refinery Program from the Ministry of Science and ICT through the National Research Foundation of Korea. < Figure: Protein engineering of key enzymes corresponding to succinic acid production. >
Highly Efficient and Stable Double Layer Solar Cel..
< (Front row from left) Professor Byungha Shin (KAIST), and PhD Candidate Daehan Kim (KAIST). (Back row from left) Professor Jin Young Kim (Seoul National University), Dr. Ik Jae Park (Seoul National University), and Professor Dong Hoe Kim (Sejong University). > Solar cells convert light into energy, but they can be inefficient and vulnerable to the environment, degrading with, ironically, too much light or other factors, including moisture and low temperature. An international research team has developed a new type of solar cell that can both withstand environmental hazards and is 26.7％ more efficient in power conversion. They published their results on March 26 in Science. The researchers, led by Byungha Shin, a professor from the Department of Materials Science and Engineering at KAIST, focused on developing a new class of light-absorbing material, called a wide bandgap perovskite. The material has a highly effective crystal structure that can process the power needs, but it can become problematic when exposed to environmental hazards, such as moisture. Researchers have made some progress increasing the efficiency of solar cells based on perovskite, but the material has greater potential than what was previously achieved. To achieve better performance, Shin and his team built a double layer solar cell, called tandem, in which two or more light absorbers are stacked together to better utilize solar energy. To use perovskite in these tandem devices, the scientists modified the material’s optical property, which allows it to absorb a wider range of solar energy. Without the adjustment, the material is not as useful in achieving high performing tandem solar cells. The modification of the optical property of perovskite, however, comes with a penalty — the material becomes hugely vulnerable to the environment, in particular, to light. To counteract the wide bandgap perovskite’s delicate nature, the researchers engineered combinations of molecules composing a two-dimensional layer in the perovskite, stabilizing the solar cells. “We developed a high-quality wide bandgap perovskite material and, in combination with silicon solar cells, achieved world-class perovskite-silicon tandem cells,” Shin said. The development was only possible due to the engineering method, in which the mixing ratio of the molecules building the two-dimensional layer are carefully controlled. In this case, the perovskite material not only improved efficiency of the resulting solar cell but also gained durability, retaining 80％ of its initial power conversion capability even after 1,000 hours of continuous illumination. This is the first time such a high efficiency has been achieved with a wide bandgap perovskite single layer alone, according to Shin. “Such high-efficiency wide bandgap perovskite is an essential technology for achieving ultra-high efficiency of perovskite-silicon tandem (double layer) solar cells,” Shin said. “The results also show the importance of bandgap matching of upper and lower cells in these tandem solar cells.” The researchers, having stabilized the wide bandgap perovskite material, are now focused on developing even more efficient tandem solar cells that are expected to have more than 30％ of power conversion efficiency, something that no one has achieved yet, “Our ultimate goal is to develop ultra-high-efficiency tandem solar cells that contribute to the increase of shared solar energy among all energy sources,” Shin said. “We want to contribute to making the planet healthier.” This work was supported by the National Research Foundation of Korea, the Korea Institute of Energy Technology Evaluation and Planning, the Ministry of Trade Industry and Energy of Korea, and the U.S. Department of Energy. Other contributors include Daehan Kim, Jekyung Kim, Passarut Boonmongkolras, Seong Ryul Pae and Minkyu Kim, all of whom affiliated with the Department of Materials Science and Engineering at KAIST. Other authors include Byron W. Larson, Sean P. Dunfield, Chuanxiao Xiao, Jinhui Tong, Fei Zhang, Joseph J. Berry, Kai Zhu and Dong Hoe Kim, all of who are affiliated with the National Renewable Energy Laboratory in Colorado. Dunfield is also affiliated with the Materials Science and Engineering Program at the University of Colorado; Berry is also affiliated with the Department of Physics and the Renewable and Sustainable Energy Institute at the University of Colorado Boulder; and Kim is also affiliated with the Department of Nanotechnology and Advanced Materials Engineering at Sejong University. Hee Joon Jung and Vinayak Dravid of the Department of Materials Science and Engineering at Northwestern University; Ik Jae Park, Su Geun Ji and Jin Young Kim of the Department of Materials Science and Engineering at Seoul National University; and Seok Beom Kang of the Department of Nanotechnology and Advanced Materials Engineering of Sejong University also contributed. < High-resolution TEM study revealing atomic configuration of the 2D passivation layers. > < Structure and photovoltaic performance for the perovskite-Si tandem device. > Image credit: Professor Byungha Shin, KAIST Image usage restrictions: News organizations may use or redistribute this image, with proper attribution, as part of news coverage of this paper only. Publication: Kim et al. (2020) “Efficient, stable silicon tandem cells enabled by anion-engineered wide band gap perovskites”. Science. Available online at https://doi.org/10.1126/science.aba3433 Profile: Byungha Shin Professor byungha＠kaist.ac.kr http://energymatlab.kaist.ac.kr/ Department of Materials Science and Engineering KAIST (END)