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Highly Efficient and Stable Double Layer Solar Cell Developed
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% 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.
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
Profile:
Daehan Kim
Ph.D. Candidate
zxzx4592@kaist.ac.kr
http://energymatlab.kaist.ac.kr/
Department of Materials Science and Engineering
KAIST
(END)
2020.03.27 View 17520 -
Team KAT Wins the Autonomous Car Challenge
(Team KAT receiving the Presidential Award)
A KAIST team won the 2018 International Autonomous Car Challenge for University Students held in Daegu on November 2.
Professor Seung-Hyun Kong from the ChoChunShik Graduate School of Green Transportation and his team participated in this contest with the team named KAT (KAIST Autonomous Technologies). The team received the Presidential Award with a fifty million won cash prize and an opportunity for a field trip abroad.
The competition was conducted on actual roads with Connected Autonomous Vehicles (CAV), which incorporate autonomous driving technologies and vehicle-to-everything (V2X) communication system.
In this contest, the autonomous vehicles were given a mission to pick up passengers or parcels. Through the V2X communication, the contest gave current location of the passengers or parcels, their destination, and service profitability according to distance and level of service difficulty.
The participating vehicles had to be equipped very accurate and robust navigation system since they had to drive on narrow roads as well as go through tunnels where GPS was not available. Moreover, they had to use camera-based recognition technology that was invulnerable to backlight as the contest was in the late afternoon.
The contest scored the mission in the following way: the vehicles get points if they pick up passengers and safely drop them off at their destination; on the other hand, points are deducted when they violate lanes or traffic lights. It will be a major black mark if a participant sitting in the driver’s seat needs to get involved in driving due to a technical issue.
Youngbo Shim of KAT said, “We believe that we got major points for technical superiority in autonomous driving and our algorithm for passenger selection.”
This contest, hosted by Ministry of Trade, Industry and Energy, was the first international competition for autonomous driving on actual roads. A total of nine teams participated in the final contest, four domestic teams and five teams allied with overseas universities such as Tsinghua University, Waseda University, and Nanyang Technological University.
Professor Kong said, “There is still a long way to go for fully autonomous vehicles that drive flexibly under congested traffic conditions. However, we will continue to our research in order to achieve high-quality autonomous driving technology.”
(Team KAT getting ready for the challenge)
2018.11.06 View 9464 -
The Medici Effect: Highly Flexible, Wearable Displays Born in KAIST
(Ph.D. candidate Seungyeop Choi)
How do you feel when technology you saw in a movie is made into reality? Collaboration between the electrical engineering and textile industries has made TVs or smartphone screens displaying on clothing a reality.
A research team led by Professor Kyung Cheol Choi at the School of Electrical Engineering presented wearable displays for various applications including fashion, IT, and healthcare. Integrating OLED (organic light-emitting diode) into fabrics, the team developed the most highly flexible and reliable technology for wearable displays in the world.
Recently, information displays have become increasingly important as they construct the external part of smart devices for the next generation. As world trends are focusing on the Internet of Things (IoTs) and wearable technology, the team drew a lot of attention by making great progress towards commercializing clothing-shaped ‘wearable displays’.
The research for realizing displays on clothing gained considerable attention from academia as well as industry when research on luminescence formed in fabrics was introduced in 2011; however, there was no technology for commercializing it due to its surface roughness and flexibility.
Because of this technical limitation, clothing-shaped wearable displays were thought to be unreachable technology. However, the KAIST team recently succeeded in developing the world’s most highly efficient, light-emitting clothes that can be commercialized.
The research team used two different approaches, fabric-type and fiber-type, in order to realize clothing-shaped wearable displays. In 2015, the team successfully laminated a thin planarization sheet thermally onto fabric to form a surface that is compatible with the OLEDs approximately 200 hundred nanometers thick. Also, the team reported their research outcomes on enhancing the reliability of operating fiber-based OLEDs. In 2016, the team introduced a dip-coating method, capable of uniformly depositing layers, to develop polymer light-emitting diodes, which show high luminance even on thin fabric.
Based on the research performance in 2015 and 2016, Ph.D. candidate Seungyeop Choi took the lead in the research team and succeeded in realizing fabric-based OLEDs, showing high luminance and efficiency while maintaining the flexibility of the fabric.
The long-term reliability of this wearable device that has the world’s best electrical and optical characteristics was verified through their self-developed, organic and inorganic encapsulation technology. According to the team, their wearable device facilitates the operation of OLEDs even at a bending radius of 2mm.
According to Choi, “Having wavy structures and empty spaces, fiber plays a significant role in lowering the mechanical stress on the OLEDs.”
“Screen displayed on our daily clothing is no longer a future technology,” said Professor Choi. “Light-emitting clothes will have considerable influence on not only the e-textile industry but also the automobile and healthcare industries.”
Moreover, the research team remarked, “It means a lot to realize clothing-shaped OLEDs that have the world’s best luminance and efficiency. It is the most flexible fabric-based light-emitting device among those reported. Moreover, noting that this research carried out an in-depth analysis of the mechanical characteristics of the clothing-spared, light-emitting device, the research performance will become a guideline for developing the fabric-based electronics industry.”
This research was funded by the Ministry of Trade, Industry and Energy and collaborated with KOLON Glotech, INC. The research performance was published in Scientific Reports in July.
(OLEDs operating in fabrics)
(Current-voltage-luminance and efficiency of the highly flexible, fabric-based OLEDs;Image of OLEDs after repetitive bending tests;Verification of flexibility through mechanical simulation)
2017.08.24 View 13831 -
KAIST Invites Entrepreneurs and Experts to Participate in a Social Technology Innovation Symposium
The Research Institute for Social Technology and Innovation (RISTI) at KAIST hosted the Social Technology Innovation Symposium on November 4, 2015 in KI building, to which 100 social business entrepreneurs and experts in the field were invited.
Social businesses refer to activities of companies, which strive to resolve social problems such as environmental issues, income inequality, and aging societies while seeking profit at the same time. This is different from companies taking social responsibility and non-profit organization serving the community in that they attempt to solve social problems through a sustainable business model.
Held under the theme of “technology capabilities of companies and social business strategies,” this symposium was the first to gather representatives from social venture companies, medium-sized enterprises, and major companies at one place to share their experiences in a social business and to discuss future tasks.
The symposium was divided into sessions with three different topics ranging from social business strategies using information technology, a social business and its business model, and social business strategies of major companies.
The symposium started with keynote speeches delivered by Professor HongKyu Lee, RISTI, and Professor Hong-Tak Lim, RISTI, who discussed the role of technology in a social business. It was followed by plenary sessions led by CEOs who are running social businesses such as the Sharing and Technologies Incorporated Project, Simwon Technology, Ecojun Company, Underdogs, and the Farming Fund as well as by representatives from a social responsibility section of CJ management team and the social responsibility council of SK. In the future, these talks will serve as a medium to share their experiences in social businesses and to discuss the role of technology in the business. Some talks touched upon topics such as development of platforms for social innovation, social businesses employing disabled workers, and crowd funding for farming.
The Director of RISTI, Professor HongKyu Lee said, “The symposium will be the first to have people from leading companies in social businesses in Korea in one place.” He added, “This will be a great opportunity for anyone to know what will be the future of social businesses, which were created to solve the social problems caused by capitalism.”
The symposium was sponsored by the Ministry of Trade, Industry, and Energy of Korea.
2015.10.30 View 7462 -
Professor Ilkwon Oh Receives the Energy Technology Innovation Award
Professor Ilkwon Oh from the Division of Ocean Systems Engineering at the School of Mechanical and Aerospace Engineering, KAIST, received the Energy Technology Innovation Award at the Energy Tech Insight 2014 Conference, which was held on August 28, 2014 at COEX in Seoul. The conference was co-hosted by the Ministry of Trade, Industry & Energy, Republic of Korea, and the Korea Institute of Energy Technology Evaluation and Planning.
Professor Oh has been recognized for his distinguished research on a synthetic technology to develop 3-dimensional carbon nanostructures based on defect engineering and for his efforts to apply this technology to produce cathode materials for high performance, high density lithium-ion secondary batteries.
In 2010, the Ministry of Education, the Republic of Korea, and the National Research Foundation of Korea included Professor Oh's research in the 100 Best Research in Basic Sciences of the Year, and the 50 Best Research in Basic Sciences in 2012 and 2014, respectively.
2014.09.07 View 8061 -
KAIST Student Awarded Prize from Energy Saving Contest
Jun-Min Kwon, an undergraduate student in the Department of Chemistry at KAIST, was awarded a prize from the Ministry of Trade, Industry and Energy, Republic of Korea, at the 35th Energy Saving Contest which was held on November 20.
The student club he has been leading was also selected as one of the best groups by the Save Energy Save Earth (SESE), a volunteer organization supported by the Korea Energy Management Corporation and the Ministry of Knowledge Economy, Republic of Korea.
Kwon began promoting energy conservation through a blog and participated in related meetings and workshops as a high school student to improve the understanding on the importance of energy saving and recycling.He also received awards from the Second National Assembly Forum on Climate Change, the Korean National Science Fair, as well as the Samsung Human Tech Paper Award.
2013.12.24 View 10845 -
KAIST Takes Steps towards a Self-Sustainable Campus
KAIST has been selected for a $45-million national smart grid initiative organized under the Ministry of Trade, Industry and Energy. Ninteen institutions will participate in the 2-year-long initiative. The consortium’s work is expected to take place from 2015 to 2017 after a review by the Ministry of Strategy and Finance.
The Smart Grid Explansion Initiative which has been considered the future of electric power industry implements information and communications technology to conventional grid system to maximize energy efficiency. The ROK government has selected the Smart Grid Expansion Initiative as one of South Korea’s primary national projects and plans to implement it nationwide based on multiple demonstration projects in major cities including Jeju.
KAIST plans to invest $45 million in developing systems for renewable energy power plants, efficient energy management, smart grid data, and electric vehicles to build the energy self-sustainable campus. It also hopes to contribute to fostering specialized talents and companies in energy management.
Byoung-Yoon Kim, the vice-president for research at KAIST, expects that by 2017, KAIST will be able to dramatically improve its energy capacity especially during peak periods and gain energy efficiency around the campus. He hopes that the micro grid project at KAIST will set a new standard for the self-sustainable campus.
2013.12.11 View 7814 -
The key to Alzheimer disease, PET-MRI made in Korea
Professor Kyu-Sung Cho
- Simultaneous PET-MRI imaging system commercialization technology developed purely from domestic technology - - Inspiring achievement by KAIST, National NanoFab Center, Sogang University, Seoul National University Hospital –
Hopes are high for the potential of producing domestic products in the field of state-of-the-art medical imaging equipment that used to rely on imported products.
The joint research team (KAIST, Sogang University and Seoul National University) with KAIST Department of Nuclear and Quantum Engineering Professor Kyu-Sung Cho in charge, together with National Nanofab Institution (NNFC; Director Jae-Young Lee), has developed PET-MRI simultaneous imaging system with domestic technology only. The team successfully acquired brain images of 3 volunteers with the newly developed system.
PET-MRI is integrated state-of-the-art medical imaging equipment that combines the advantages of Magnetic Resonance Imaging (MRI) that shows anatomical images of the body and Position Emission Tomography (PET) that analyses cell activity and metabolism. Since the anatomical information and functional information can be seen simultaneously, the device can be used to diagnose early onset Alzheimer’s disease and is essential in biological science research, such as new medicine development.
The existing equipment used to take MRI and PET images separately due to the strong magnetic field generated by MRI and combine the images. Hence, it was time consuming and error-prone due to patient’s movement. There was a need to develop PET that functions within a magnetic field to create a simultaneous imaging system.
The newly developed integral PET-MRI has 3 technical characteristics: 1. PET detector without magnetic interference, 2. PET-MRI integration system, 3.PET-MRI imaging processing.
The PET detector is the most important factor and accounts for half the cost of the whole system. KAIST Professor Cho and NNFC Doctor Woo-Suk Seol’s team successfully developed the Silicon Photomultiplier (amplifies light coming into the radiation detector) that can be used in strong magnetic fields. The developed sensor has a global competitive edge since it optimises semiconductor processing to yield over 95% productivity and around 10% gamma radiation energy resolving power.
Sogang University Department and Electrical Engineering Professor Yong Choi developed cutting edge PET system using a new concept of electric charge signal transmission method and imaging location distinction circuit. The creativity and excellence of the research findings were recognised and hence published on the cover of Medical Physics in June.
Seoul National University Hospital Department of Nuclear Medicine Professor Jae-Sung Lee developed the Silicon Photomultiplier sensor based PET imaging reconstitution programme, MRI imaging based PET imaging revision technology and PET-MRI imaging integration software.
Furthermore, KAIST Department of Electrical Engineering Professor Hyun-Wook Park was responsible for the development of RF Shielding technology that enables simultaneous installation of PET and MRI and using this technology, he developed a head coil for the brain that can be connected to PET for installation.
Based on the technology describe above, the joint research team successfully developed PET-MRI system for brains and acquired PET-MRI integrated brain images from 3 volunteers last June.
In particular, this system has the distinct feature of a detachable PET module and MRI head coil to the existing whole body MRI, so that PET-MRI simultaneous imaging is possible with low installation cost.
Professor Cho said, “We have prepared the foundation of domestic commercial PET and the system has a competitive edge in the global market of PET-MRI system technology.” He continued, “It can reduce the cost of the increasing brain related disease diagnosis, including Alzheimer’s, dramatically.”
Funded by Ministry of Trade, Industry and Energy as an Industrial Foundation Technology Development Project (98 billion won in 7 years), the research applied for over 20 patents and 20 CSI theses.
Figure 1.Brain phantom images from developed PET-MRI system
Figure 2. Brain images from developed PET-MRI system
Figure 3. Domestic PET-MRI clinical trial
Figure 4. Head RF coil and PET detector inserted in MRI
Figure 5. Insertion type PET detector module
Figure 6. Silicon Photomultiplier sensor (Left) and flash crystal block (right)
Figure7. Silicon Photomultiplier sensor
Figure 8. PET detection principle
2013.11.28 View 12457 -
KAIST student wins Aerospace Student Papers Grand Prize
Dong-Il Yoo, a doctoral candidate under Professor Hyun-Chul Shim, at the Department of Aerospace Engineering, KAIST, has been awarded the Second Prize Award at the 11th Korea Aerospace Industries (KAI) Paper Contest. The award ceremony was held on October 30th at the media conference room at the KINTEX ADEX 2013 Exhibition in Seoul.
Yoo"s paper, titled "A Study on Virtual Pursuit Point-based Autonomous Air Combat Guidance Law for UCAV," is highly regarded for originality and creativity. The Field Robotics Center at the KAIST Institute, where Yoo conducted his research, also received the first prize at the 7th KAI Paper Contest.
The KAI Paper Contest was first organized in 2003 to promote academic interest and advance research and development in aerospace engineering among university students.
The KAI Paper Contest is one of the most prestigious contests in Korea. It is sponsored by the Ministry of Trade, Industry and Energy, the Ministry of Land, Infrastructure and Transport, the Korean Society for Aeronautical and Space Sciences, the Korea Aerospace Industries Association, and the Korea Civil Aviation Development Association.
Dong-Il Yoo (left) and Professor Hyun-Chul Shim (right)
2013.11.11 View 11016