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Research trend of cascade heat pumps

Science China(Technological Sciences) 2017年第11期60卷 1597-1615页

作者： BOAHEN Samuel choi jongmin Graduate School of Mechanical Engineering Hanbat National UniversityDaejeon 34158Korea Department of Mechanical Engineering Hanbat National UniversityDaejeon 34158Korea

Most commercial and industrial facilities require very low temperatures for refrigeration and high temperatures for space heating and hot water purposes. Single stage heat pumps have not been able to meet these temperature demands and have been characterized by low capacities and coefficient of performance(COP). Cascade heat pump has been developed to overcome the weaknesses of single stage heat pumps. This study reviews recent works done by researchers on cascade heat pumps for refrigeration, heating and hot water generation. Selection of suitable refrigerants to meet the pressure and temperature demands of each stage of the cascade heat pump has been discussed. Optimization of design parameters such as intermediate temperature(low stage condensing and high stage evaporating temperatures), and temperature difference in the cascade heat exchanger for optimum performance of the cascade heat pump has been reviewed. It was found that optimising each design parameter of the cascade heat pump is necessary for maximum system performance and this may improve the exergetic efficiency, especially of cascade refrigeration systems, by about 30.88%. Cascade heat pumps have wider range of application especially for artificial snow production, in the supermarkets,for natural gas liquefaction, in drying clothes and food and as heat recovery system. The performance of cascade heat pumps can be improved by 19% when coupled with other renewable energy sources for various real time applications. Also, there is the need for much research on refrigerant charge amount of cascade heat pumps, refrigerant-refrigerant heat exchangers to be used as cascade heat exchanger, cascade heat pumps for simultaneous cooling, heating and hot water generation and on the use of variable speed compressors and their control strategies in matching system capacity especially at part load conditions.

关键词： cascade heat pump low stage high stage optimization system performance refrigerant

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Infrared-harvesting colloidal quantum dot inks for efficient photovoltaics: Impact of surface chemistry and device engineering

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Journal of Materials Science & Technology 2023年第16期147卷 224-240页

作者： Younghoon Kim Min-Jae choi jongmin choi Department of Chemistry Kookmin UniversitySeoul02707Republic of Korea Department of Chemical and Biochemical Engineering Dongguk UniversitySeoul04620Republic of Korea Department of Energy Science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu42988Republic of Korea

Colloidal quantum dots(CQDs)are promising semiconducting materials,which can be used as a photoactive layer in various optoelectronic applications,because of their size-tunable bandgap energy,solution processability,and excellent optical and optoelectronic *** particular,these features have generated great interest in the development of CQD solar cells and led to a rapid increase in their power conversion *** improvements were enabled by many innovative approaches in terms of CQD’s surface chemistry and device architecture *** this review,a critical overview of the research progress in CQD solar cells is presented with a focus on the strategies adopted for achieving record efficiency in CQD solar *** strategies include the use of organic/inorganic surface ligands,pre-and post-treatment of CQDs,and solid-state/solution-phase ligand ***,we provide an understanding of the research history to inspire the rational design of next-generation CQD optoelectronic devices,such as solar cells,light-emitting diodes,and *** research on the development of infrared CQD solar cells as complementary platforms to other solar cell technologies is also critically discussed to provide another perspective on CQD technologies.

关键词： Quantum dot Lead sulfide Ligand exchange Colloidal ink Infrared light Solar cell

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High-Performance Perovskite Quantum Dot Solar Cells Enabled by Incorporation with Dimensionally Engineered Organic Semiconductor

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Nano-Micro Letters 2022年第12期14卷 272-285页

作者： Seyeong Lim Dae Hwan Lee Hyuntae choi Yelim choi Dong Geon Lee Sung Beom Cho Seonkyung Ko jongmin choi Younghoon Kim Taiho Park Department of Chemical Engineering Pohang University of Science and Technology(POSTECH)Pohang 37673Republic of Korea Department of Materials Science and Engineering Hanyang UniversitySeoul 04763Republic of Korea Center of Materials Digitalization Korea Institute of Ceramic Engineering and Technology(KICET)Jinju 52851Republic of Korea Department of Materials Science and Engineering Ajou UniversitySuwon 16499Republic of Korea Department of Energy Science and Engineering Daegu Gyeongbuk Institute of Science and Technology(DGIST)Daegu 42988Republic of Korea Department of Chemistry Kookmin UniversitySeoul 02707Republic of Korea

Perovskite quantum dots(PQDs)have been considered promising and effective photovoltaic absorber due to their superior optoelectronic properties and inherent material merits combining perovskites and ***,they exhibit low moisture stability at room humidity(20-30%)owing to many surface defect sites generated by inefficient ligand exchange *** surface traps must be re-passivated to improve both charge transport ability and moisture *** address this issue,PQD-organic semiconductor hybrid solar cells with suitable electrical properties and functional groups might dramatically improve the charge extraction and defect *** organic semiconductors are typically low-dimensional(1D and 2D)and prone to excessive self-aggregation,which limits chemical interaction with *** this work,we designed a new 3D star-shaped semiconducting material(Star-TrCN)to enhance the compatibility with *** robust bonding with Star-TrCN and PQDs is demonstrated by theoretical modeling and experimental *** Star-TrCN-PQD hybrid films show improved cubic-phase stability of CsPbI_(3)-PQDs via reduced surface trap states and suppressed moisture *** a result,the resultant devices not only achieve remarkable device stability over 1000 h at 20-30%relative humidity,but also boost power conversion efficiency up to 16.0%via forming a cascade energy band structure.

关键词： CsPbI3 quantum dots Star-shaped organic semiconductors Hybrid perovskite quantum dots Solar cell stability High-efficiency photovoltaics

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Highly ordered lead-free double perovskite halides by design

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Journal of Materiomics 2020年第4期6卷 651-660页

作者： Chang Won Ahn Jae Hun Jo Jong Chan Kim Hamid Ullah Sangkyun Ryu Younghun Hwang Jin San choi jongmin Lee Sanghan Lee Hyoungjeen Jeen Young-Han Shin Hu Young Jeong Ill Won Kim Tae Heon Kim Department of Physics and Energy Harvest-Storage Research Center(EHSRC) University of UlsanUlsan44610Republic of Korea UNIST Central Research Facilities(UCRF)&School of Materials Science and Engineering Ulsan National Institute of Science and Technology(UNIST)Ulsan44919Republic of Korea Multiscale Materials Modelling Laboratory Department of PhysicsUniversity of UlsanUlsan44610Republic of Korea Department of Physics Pusan National UniversityPusan46241Republic of Korea School of Electrical and Electronics Engineering Ulsan CollegeUlsan44610Republic of Korea School of Materials Science and Engineering Gwangju Institute of Science and TechnologyGwangju61005Republic of Korea

Lead-free double perovskite halides are emerging optoelectronic materials that are alternatives to leadbased perovskite ***,single-crystalline double perovskite halides were synthesized,and their intriguing functional properties were *** such pioneering works,lead-free double perovskite halides with better crystallinity are still in demand for applications to novel optoelectronic ***,we realized highly crystalline Cs2AgBiBr6 single crystals with a well-defined atomic ordering on the microscopic *** avoided the formation of Ag vacancies and the subsequent secondary Cs3Bi2Br9 by manipulating the initial chemical environments in hydrothermal *** suppression of Ag vacancies allows us to reduce the trap density in the as-grown crystals and to enhance the carrier mobility *** design strategy is applicable for fabricating other lead-free halide materials with high crystallinity.

关键词： Cs2AgBiBr6 Lead-free Double perovskite Single crystal

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High-intensity laser-driven particle and electromagnetic wave sources for science, industry, and medicine

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Frontiers of Optoelectronics 2009年第3期2卷 299-303页

作者： Akito SAGISAKA Hiroyuki DAIDO Alexander S.PIROZHKOV Michiaki MORI Akifumi YOGO Koichi OGURA Satoshi ORIMO Mamiko NISHIUCHI Jinglong MA Hiromitsu KIRIYAMA Shuhei KANAZAWA Shuji KONDO Yoshiki NAKAI Takuya SHIMOMURA Manabu TANOUE Atsushi AKUTSU Hajime OKADA Tomohiro MOTOMURA Tetsuya KAWACHI Sergei V.BULANOV Timur Zh.ESIRKEPOV Shigeki NASHIMA Makoto HOSODA Hideo NAGATOMO Yuji OISHI Koshichi NEMOTO Il Woo choi Seong Ku LEE jongmin LEE Advanced Photon Research Center and Photo-Medical Research Center Japan Atomic Energy Agency A.M.Prokhorov Institute of General Physics Russian Academy of Sciences Moscow Institute of Physics and Technology Department of Applied Physics Graduate School and Faculty of Engineering Osaka City University Institute of Laser Engineering Osaka University Central Research Institute of Electric Power Industry Advanced Photonics Research Institute Gwangju Institute of Science and Technology

We simultaneously observed both the fast proton generation and terahertz(THz) radiation in the laser pulse interaction with a thin-foil target. The maximum proton energy of ～2.3 Me V and an intense THz radiation were observed at the pulse duration of～30 fs. We also measured the proton beam and UV harmonics from a thin-foil target by changing the laser pulse duration. In the case of the ～500 fs, peaks of UV harmonics up to fourth order appeared. This unique combination of the multiple beams will provide useful applications such as pump-probe experiments.

关键词： high-intensity laser thin-foil target plasma proton electromagnetic wave

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