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Surface-functionalized hole-selective monolayer for high efficiency single-junction wide-bandgap and monolithic tandem perovskite solar cells

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Journal of Energy Chemistry 2024年第1期88卷 317-326,I0008页

作者： Devthade Vidyasagar Yeonghun Yun Jae Yu Cho Hyemin Lee Kyung Won Kim Yong Tae Kim sung woong yang Jina Jung Won Chang Choi Seonu Kim Rajendra Kumar Gunasekaran Seok Beom Kang Kwang Heo Dong Hoe Kim Jaeyeong Heo Sangwook Lee School of Materials Science and Engineering Kyungpook National UniversityDaegu 41566Republic of Korea Department of Materials Science and Engineering and Optoelectronics Convergence Research CenterChonnam National UniversityGwangju 61186Republic of Korea Department of Materials Science and Engineering Korea UniversitySeoul 02841Republic of Korea Department of Nanotechnology and Advanced Materials Engineering Sejong UniversitySeoul 05006Republic of Korea

Carbazole moiety-based 2PACz([2-(9H-carbazol-9-yl)ethyl]phosphonic acid)self-assembled monolayers(SAMs)are excellent hole-selective contact(HSC)materials with abilities to excel the charge-transferdynamics of perovskite solar cells(PSCs).Herein,we report a facile but powerful method to functionalize the surface of 2PACz-SAM,by which reproducible,highly stable,high-efficiency wide-bandgap PSCs can be *** 2PACz surface treatment with various donor number solvents improves assembly of 2PACz-SAM and leave residual surface-bound solvent molecules on 2PACz-SAM,which increases perovskite grain size,retards halide segregation,and accelerates hole *** surface functionalization achieves a high power conversion efficiency(PCE)of 17.62%for a single-junction wide-bandgap(~1.77 e V)*** also demonstrate a monolithic all-perovskite tandem solar cell using surfaceengineered HSC,showing high PCE of 24.66%with large open-circuit voltage of 2.008 V and high fillfactor of 81.45%.Our results suggest this simple approach can further improve the tandem device,when coupled with a high-performance narrow-bandgap sub-cell.

关键词： Perovskite solar cells 2PACz Monolithic tandem solar cells Wide bandgap

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High-performance self-powered color filter-free blue photodetector based on wide-bandgap halide perovskites

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Journal of Materials Science & Technology 2023年第21期152卷 100-108页

作者： Yeonghun Yun Hanbyeol Cho Jina Jung sung woong yang Devthade Vidyasagar Rajendra Kumar Gunasekaran Sangwook Lee School of Materials Science and Engineering Kyungpook National University(KNU)Daegu 41566South Korea KNU Advanced Material Research Institute Kyungpook National UniversityDaegu 41566South Korea Institute of Microstructure Technology&Light Technology Institute Karlsruhe Institute of TechnologyKarlsruhe 76131Federal Republic of Germany

Blue photodetectors(PDs)are attracting great attention for various *** blue PDs based on inorganic GaP or InGaN absorbers are limited by their expensive,complex,and high-temperature fabrication *** absorber-based blue PDs still have much lower photode-tecting properties than inorganic blue *** this study,a high-performance self-powered blue PD is developed using methylammonium lead halide(MAPbX_(3);X=I,Br,and Cl)perovskites based on the eco-nomic and facile solution process at low *** composition is obtained through halide-composition *** best-performing device exhibits an average external quantum efficiency and an average detectivity of 42.7%and 8.65×10^(11) Jones,respectively,within the blue *** peak responsivity of the proposed PD is 0.174 A W^(−1) at 455 nm,which is comparable to that of commercial gallium phosphide blue PD(0.180 A W^(−1) at 470 nm).Moreover,the proposed device exhibits excellent environmental stability under ambient air *** findings will act as a basis for next-generation image sensor technologies,such as vertically stacked red/green/blue PDs.

关键词： Perovskites Photodetectors Blue Composition engineering Self-powered Wide bandgap

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High-throughput compositional mapping of triple-cation tin-lead perovskites for high-efficiency solar cells

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InfoMat 2023年第4期5卷 25-38页

作者： Rajendra Kumar Gunasekaran Jina Jung sung woong yang Jungchul Yun Yeonghun Yun Devthade Vidyasagar Won Chang Choi Chang-Lyoul Lee Jun Hong Noh Dong Hoe Kim Sangwook Lee School of Materials Science and Engineering Kyungpook National UniversityDaeguRepublic of Korea Advanced Photonics Research Institute(APRI) Gwangju Institute of Science and Technology(GIST)GwangjuRepublic of Korea School of Civil Environmental and Architectural EngineeringGreen SchoolKorea UniversitySeoulRepublic of Korea Department of Materials Science and Engineering Korea UniversitySeoulRepublic of Korea

Mixed tin-ead perovskites suffer from structural instability and rapid tin oxidation;thus,the investigation of their optimal composition ranges is important to address these inherent *** critical role of triple cations in mixed Sn–Pb iodides is studied by performing a wide range of compositional screenings over mechanochemically synthesized bulk and solution-processed thin films.A ternary phase map of FA(Sn_(0.6)Pb_(0.4))I_(3),MA(Sn_(0.6)Pb_(0.4))I_(3),and Cs(Sn_(0.6)Pb_(0.4))I_(3)is formed,and a promising composition window of(FA_(0.6-x)MA_(0.4)Cs_(x))Sn_(0.6)Pb_(0.4)I_(3)(0≤x≤0.1)is demonstrated through phase,photoluminescence,and stability *** cell performance and chemical stability across the targeted compositional space are investigated,and FA_(0.55)MA_(0.4)Cs_(0.05)Sn_(0.6)Pb_(0.4)I_(3)with strain-relaxed lattices,reduced defect densities,and improved oxidation stability is *** inverted perovskite solar cells with the optimal composition demonstrate a power conversion efficiency of over 22%with an open-circuit voltage of 0.867 V,which corresponds to voltage loss of 0.363 V,promising for the development of narrow-bandgap perovskite solar cells.

关键词： compositional engineering mixed tin-ead iodides narrow-bandgap perovskites perovskite solar cells strain relaxation ternary phase mapping

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Ruptured venous aneurysm associated with a dural arteriovenous fistula:Two case reports

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World Journal of Clinical Cases 2024年第29期12卷 6314-6319页

作者： You Sub Kim woong Yoon Byung Hyun Baek Seul Kee Kim sung Pil Joo Tae Sun Kim Department of Neurosurgery Chonnam National University Hospital and Medical SchoolGwangju 61469South Korea Department of Radiology Chonnam National University Hospital and Medical SchoolGwangju 61469South Korea Department of Radiology Chonnam National University Hwasun HospitalHwasungun 58128South Korea

BACKGROUND In general,venous aneurysm associated with dural arteriovenous fistula(dAVF)is considered to be developed under long standing venous hypertension and manifested as venous ectasia of draining vein ***,discrete saccular shaped venous aneurysm without angiographic evidence of venous hypertension arising from the draining vein,like cerebral arterial aneurysm,is quite rare and its pathomechanism remains unclear in patients with *** SUMMARY In this report,we present two cases of ruptured saccular venous aneurysms associated with dAVF without venous hypertension or venous *** both cases,significant curve or stenosis is observed in draining vein,which is located in just distal portion of the venous *** aneurysms were successfully treated with a transarterial *** mechanism of venous aneurysms in these cases is *** Although there is little doubt that hemodynamic stress has a critical role in the development of venous aneurysms in patients with dAVF,preceding venous hypertension or venous ectasia is not necessary for development and enlargement of venous *** the significant risk of rupture,a careful review of draining vein features including tortuosity or stenosis is needed,especially in venous aneurysms without evidence of venous hypertension.

关键词： Dural arteriovenous fistula Venous aneurysm Hemodynamic stress Intracranial hemorrhage Embolization Case report

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Effective shape-controlled growth of monolayer MoS2 flakes by powder-based chemical vapor deposition

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Nano Research 2017年第1期10卷 255-262页

作者： Sang Yoon yang Gi woong Shim Seung-Bum Seo sung-Yool Choi Graphene Research Center (GRC) Center for Advanced Materials Discovery for 3D Displays (CAMD3) School of Electrical EngineeringKorea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea

In the recent years, transition-metal dichalcogenides such as MoS2 have attracted considerable attention owing to their unique structure and electronic properties. Chemical vapor deposition （CVD） is a popular method for producing MoS2 flakes with different shapes. Here, we report an effective method for achieving a broad range of shape evolution in CVD-grown monolayer MoS2 flakes. By controlling the S and MoO3 temperatures, the shape of the monolayer MoS2 flakes was varied from hexagonal to triangular via intermediate shapes such as truncated and multi-apex triangles. The shape evolution of the MoS2 flakes can be explained by introducing the term “nominal Mo：S ratio”, which refers to the amount of loaded MoO3 and evaporated S powders. By using the nominal Mo：S ratio, we predicted the potential reaction atmosphere and effectively controlled the actual proportion of MoO3-x with respect to S in the growth region, along with the growth temperature. From the systematic investigation of the behavior of the shape evolution, we developed a shape-evolution diagram, which can be used as a practical guide for producing CVD-grown MoS2 flakes with desired shapes

关键词： molybdenum disulfide CVD growth shape evolution diagram growth condition

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The validity of the Reynolds equation in spool valve analysis considering cavitation

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Friction 2016年第3期4卷 266-276页

作者： sung-Ho HONG Kyung-woong KIM School of Mechanical Aerospace & Systems Engineering Korea Advanced Institute of Science and Technology 291 Daehak-ro Yuseong-guDaejeon 305-701 Republic of Korea

The purpose of this research is to investigate the validity of the Reynolds equation in spool valve analysis under cavitation. This study is carried out for a laminar and isothermal flow between a sleeve and spool with grooves. The pressure and lateral force obtained from the Reynolds equation and the Navier-Stokes equation are compared with variations of aspect ratio, cross sectional area, and number of grooves. The cavitation phenomenon is considered by using a cavitation model in the Navier-Stokes equation and the Reynolds cavitation boundary condition in the Reynolds equation. A large difference of more than 20% is found between the equations for a lateral force of spool valve with many grooves. It was found that the Reynolds equation is not suitable for calculation of a lateral force of the spool valve with multiple-grooves of which the width and depth are even larger than the clearance under cavitation.

关键词： validity Reynolds equation Navier-Stokes equation spool valve cavitation

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Aging Analysis Framework of Windows-Based Systems through Differential-Analysis of System Snapshots

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Computers, Materials & Continua 2022年第12期73卷 5091-5102页

作者： Eun-Tae Jang sung Hoon Baek Ki-woong Park SysCore Lab Sejong UniversitySeoul05006Korea Department of Computer System Engineering Jungwon UniversityChungcheongbuk-do28024Korea

When aWindows-based system is used for an exceedingly long time,its performance degrades,and the error occurrence rate tends to *** is generally called system *** investigate the reasons for system aging,various studies have been conducted within the range of the operating system kernel to the user ***,finding an accurate reason for system performance degradation remains challenging research *** this study,system monitoring was conducted by dividing a system into‘before software installation,’‘after software installation,’and‘after software removal.’We confirmed that when a software installed in a system is removed,various system elements,such as storage and memory,are not restored to the level prior to the software ***,we established a hypothesis regarding the performance degradation of a computer system owing to repeated software installation/removal operations,investigated the correlation between system aging and repeated software installation/removal operations,and proposed a system aging analysis framework for analyzing the reason behind system *** the proposed system aging analysis framework,we aim to forcibly age a Windows-based system by repeating the software installation/removal operation by utilizing the system forced aging *** framework identifies the elements affecting system performance through a differential data analysis of the system time-series data extracted by the system performance extraction and system component snapshot ***,the aging analysis framework presented in this study is expected to be effectively utilized as an index for studying system aging.

关键词： System aging virtual machine system analysis

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Ultrasonic Approach of Rayleigh Pitch-Catch Contact Ultrasound Waves on CFRP Laminated Composites

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Journal of Materials Science & Technology 2008年第3期24卷 407-409页

作者： In-Young yang Kwang-Hee Im Uk Heo David K Hsu Je-woong Park Hak-Joon Kim sung-Jin Song School of Mechanical Eng. Chosun Univ Department of Automotive Eng. Woosuk Univers-ity Center for Nondestructive Evaluation Iowa State University Dept.of Naval Arch.and Ocean Eng. Chosun Univ School of Mechanical Eng. Sungkyunkwan University

CFRP （carbon fiber reinforced plastics） composite materials have wide applicability because of their inherent design flexibility and improved material properties. However, impacted composite structures have 50%-75% less strength than undamaged structures. In this work, a CFRP composite material was nondestructively characterized in order to ensure product quality and structural integrity of CFRP and one-sided pitch-catch technique was developed to measure impacted-damaged area by using an automated-data acquisition system in an immersion tank. A pitch-catch signal was found to be more sensitive than normal incidence backwall echo of longitudinal wave under defect conditions in the composite.

关键词： Impact damages C-scanner Carbon fiber reinforced plastics (CFRP) Pitchcatch mode

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Graphene electrode with tunable charge transport in thin-film transistors

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Nano Research 2018年第1期11卷 274-286页

作者： Ick-Joon Park Tae In Kim In-Tak Cho Chang-Woo Song Ji-woong yang Hongkeun Park Woo-Seok Cheong sung Gap Im Jong-Ho Lee sung-Yool Choi School of Electrical Engineering GrapheneY2D Materials Research Center Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea Department of Electrical Engineering Seoul National University Seou108826 Republic of Korea Electronics and Telecommunications Research Institute Daejeon 34129 Republic of Korea Department of Chemical and Biomolecular Engineering Graphene/2D Materials Research Center Korea Advanced Institute of Science and Technology (KAIST) Daejeon 34141 Republic of Korea

Graphene, a single atomic layer of sp2-hybridized carbon, has immense potential as a transparent conducting material in electronic applications owing to its superior properties, including optical transparency and high conductivity. Particularly, the tunable work function of graphene enables the integration of graphene electrodes with various electronic devices. To achieve high performance in graphene-based devices, effective charge transport between the graphene electrode and the semiconducting material needs to be optimized; this is closely related to the modulation of the Schottky barrier （SB）. In this study, we investigate the ~nable charge transport properties as a function of graphene doping in n-channel thin-film transistors （TFTs） in terms of the electrical characteristics and low-frequency noise （LFN） behaviors. Alkali metal carbonates tuned the work function of graphene, resulting in a dramatic decrease in the SB and an improvement of the carrier injection in n-channel TFTs. The electrical performance of the TFTs was evaluated by extraction of the field-effect mobilities and ratio of contact resistance to total resistance. Furthermore, the level of contact noise created by the barrier height fluctuation and relative contribution of channel noise and contact noise in the TFTs was investigated by LFN measurements to demonstrate the ~nable charge transport. Our findings therefore provide new insights into the tunable charge transport mechanism in graphene-based devices and reveal the immense potential of graphene as electrodes in high performance flexible and transparent displays.

关键词： charge transport graphene doping Schottky barrier work function contact property low-frequency noise

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2D reduced graphene oxide-titania nanocomposites synthesized under different hydrothermal conditions for treatment of hazardous organic pollutants

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Particuology 2018年第1期16卷 165-173页

作者： Migyeong Kim Won-Hwa Hong woong Kim sung Hyuk Park Wan-Kuen Jo Department of Environmental Engineering Kyungpook National University Daegu 702-701 Republic of Korea School of Architecture Kyungpook National University Daegu 702-701 Republic of Korea Department of Materials Science and Metallurgical Engineering Kyungpook National University Daegu 702-701 Republic of Korea

Two-dimensional reduced graphene oxide-titania （RGO-TiO2） composites were prepared using a single- step hydrothermal method under various hydrothermal reaction conditions. The morphological and surface characteristics of the RGO-TiO2 composites and reference materials were determined. The RGO-TiO2 composites showed photocatalytic activity for the decomposition of two target pollutants that was superior to both pure TiO2 and RGO under fluorescent daylight lamp illumination. The photo- catalytic activity of the RGO-TiO2 composite increased as the hydrothermal treatment time increased from 1 to 24 h, but then it decreased as the time increased to 36 h, which indicated the presence of an optimal treatment time. RGO-TiO2 composites activated by violet light-emitting diodes （LEDs） displayed lower decomposition efficiency than those activated by a daylight lamp, likely because of the lower light intensity of violet LEDs （0.2 mW/cm2） when compared with that of the daylight lamp （1.4mW/cm2）. However, the photocatalytic decomposition of the target pollutants using the RGO-TiO2 composite was more energy-efficient using the violet LEDs. The photocatalytic reaction rates increased as the residence time decreased, whereas the reverse was true for the decomposition efficiency.

关键词： TiO2 composite Continuous-flow mode Hydrothermal time VioletLight emitting diode

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