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Enhanced UV stability of perovskite solar cells with a SrO interlayer
Lee, Sang-Won,Kim, Seongtak,Bae, Soohyun,Cho, Kyungjin,Chung, Taewon,Hwang, Jae-Keun,Song, Inseol,Lee, Wonkyu,Park, Sungeun,Jung, Jaebong,Chun, Jihun,Lee, Yoon Jung,Moon, Yeon Ji,Lee, Hae-Seok,Kim, Do Elsevier 2018 Organic Electronics Vol.63 No.-
<P><B>Abstract</B></P> <P>We investigated strontium oxide (SrO) as an interlayer material to enhance the UV stability of a CH<SUB>3</SUB>NH<SUB>3</SUB>PbI<SUB>3</SUB> perovskite solar cell. Moisture and over 400 nm wavelength of light were excluded to investigate the effect of UV light only. Two different interlayer fabrication processes were examined to optimize the performance of this solar cell. Devices fabricated by dipping for 30 min in SrO solution exhibited photoconversion efficiencies of 15.5%, whereas those fabricated with 60-min dipping showed photoconversion efficiencies of 15% and exhibited local Sr agglomeration. Devices with SrO displayed lower initial efficiencies than those without any SrO layer (17.6%), However, a device without SrO retained only 34.4% of its initial efficiency after 100 h of UV exposure. In contrast, SrO-incorporated devices retained almost 60.0% of their initial efficiency. Severe μ-PL mapping intensity degradation was observed in devices that did not include the interlayer, but no degradation was observed in those with the SrO interlayer. This can be attributed to the passivation of the degradation sites by SrO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Perovskite UV stability was tested under conditions except moisture, oxygen and wavelengths exceeding 400 nm. </LI> <LI> With high resolution μ-PL mapping technique, direct evidence is provided about the area perovskite UV degradation begins. </LI> <LI> UV degradation is initiated at the ETL/perovskite interface. </LI> <LI> Effect of the SrO interlayer on UV stability was examined in an inert atmosphere. </LI> <LI> UV stability is enhanced by SrO interface passivation. </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
POMY: 햅틱 피드백을 적용한 몰입형 영어 학습 시스템
이재봉(Jaebong Lee),이규송(Kyusong Lee),Hoang Minh Phuong,이호진(Hojin Lee),이근배(Gary Geunbae Lee),최승문(Seungmoon Choi) 제어로봇시스템학회 2014 제어·로봇·시스템학회 논문지 Vol.20 No.8
In this paper, we propose a novel CALL (Computer-Assisted Language Learning) system, which is called POMY (POSTECH Immersive English Study). In our system, students can study English while talking to characters in a computer-generated virtual environment. POMY also supports haptic feedback, so students can study English in a more interesting manner. Haptic feedback is provided by two platforms, a haptic chair and a force-feedback device. The haptic chair, which is equipped with an array of vibrotactile actuators, delivers directional information to the student. The force-feedback device enables the student to feel the physical properties of an object. These haptic systems help the student better understand English conversations and focus on studying. We conducted a user experiment and its results showed that our haptic-enabled English study contributes to better learning of English.
Total synthesis of (−)-deguelin <i>via</i> an iterative pyran-ring formation strategy
Lee, Seungbeom,An, Hongchan,Chang, Dong-Jo,Jang, Jaebong,Kim, Kyeojin,Sim, Jaehoon,Lee, Jeeyeon,Suh, Young-Ger The Royal Society of Chemistry 2015 Chemical communications Vol.51 No.43
<P>Enantioselective synthesis of (-)-deguelin was accomplished via an iterative pyran-ring formation approach. The key features involve the anionic addition of a chromene unit to aryloxy alkyl aldehyde for the double cyclization precursor and iterative pyran ring formation by Pd-catalyzed O-arylation and C-arylation, respectively.</P>
Aging and UV Irradiation Related Changes of Gene Expression in Primary Human Keratinocytes
Lee, Ok Joo,Lee, Sung-Young,Park, Jae-Bong,Lee, Jae-Yang,Kim, Jong-Il,Kim, Jaebong Korea Genome Organization 2005 Genomics & informatics Vol.3 No.2
The epidermis is a physiological barrier to protect organisms against environment. During the aging process, skin tissues undergo various changes including morphological and functional changes. The transcriptional regulation of genes is part of cellular reaction of aging process. In order to examine the changes of gene expression during the aging process, we used the primary cell culture system of human keratinocytes. Since UV radiation is the most important environmental skin aggressor, causing skin cancer and other problems including premature skin aging, we examined the changes of gene expression in human keratinocytes after UV irradiation using oligonucleotide microarray containing over 10,000 genes. We also compared the gene expression patterns of the senescent and UV treated cells. Expression of the variety of genes related to transcription factors, cell cycle regulation, immune response was altered in human keratinocytes. Some of down-regulated genes are represented in both senescent and UV treated cells. The results may provide a new view of gene expression following UVB exposure and aging process in human keratinocytes.
국가수준 학업성취도 평가 서답형 문항에 대한 응답 특성 분석 - 과학과 생명 영역을 중심으로 -
이재봉 ( Jaebong Lee ),심규철 ( Kew-cheol Shim ) 한국생물교육학회 2021 생물교육 Vol.49 No.3
This study aims to examine the response characteristics of middle school students on the constructed response items related to life science of National Assessment of Educational Achievement (NAEA). The response characteristics on the constructed response items of 2018 NAEA were analyzed comparatively according to score type, correct answer-rate, and achievement level. The results suggested that middle school students have a lack of knowledge about basic concepts of science. Most of middle school students were found to have the ability to understand and simply express the problem situations of the short-answer assessment problem. However they were found to be insufficient of the ability to think comprehensively by relating the problem situations to scientific concepts. The results suggested that the lesson should be needed to improve the understanding of basic scientific concepts and the reasoning of utilizing scientific concepts in the inquiry context. It is necessary to enforce the connection between instruction and assessment alignment in school science, and to encourage science teachers to utilize the constructed response assessment problems. They can carry out the detailed feedback and strategies for science teaching and learning on the basis of the students’ response characteristics on the constructed response assessment problems.
POM 마찰 및 마모에 대한 마이크로 표면 텍스처링의 영향
이재봉(Jaebong Lee),조민행(Minhaeng Cho) 한국트라이볼로지학회 2009 한국트라이볼로지학회지 (Tribol. Lubr.) Vol.25 No.3
The effect of micro-cavities fabricated using laser surface texturing (LST) technique on polyoxymethylene (POM) surface was studied in terms of heat affected zone (HAZ), cavity geometry, surface roughness, deformation of cavity along with sliding cycles, and tribological characteristics. Cavity process parameters were lamp current, process time, and the stream of air used to minimize the flow of molten polymer into cavity. Especially, the deformation of cavity geometry was extensively studied to provide deep insight into morphological analysis of the cavities. Also, this paper presents the behavior of friction and wear of POM specimens as a function of sliding cycles.