Publications by authors named "Jincheol Kim"

12 Publications

  • Page 1 of 1

Deciphering van der Waals interaction between polypropylene and carbonated fly ash from experimental and molecular simulation.

J Hazard Mater 2021 Jul 24;421:126725. Epub 2021 Jul 24.

Department of Chemistry and Chemical Engineering, Education and Research Center for Smart Energy and Materials, Inha University, Incheon 22212, South Korea. Electronic address:

Pollution emitted from power plants, including a considerable amount of fly ash (FA) and carbon dioxide (CO), annually increases and is challenging from an environmentally friendly and sustainable point of view. To date, laboratory-scaled approaches cannot efficiently replace the FA-landfilling and mitigate the stress from CO emission. Here, a practically operatable fundamental work by combining carbonated FA (C-FA)-immobilizing CO in FA-and polypropylene (PP) matrix is reported and reveals abnormal mechanical and thermal features clarified by calculating van der Waals (vdW) interaction from an atomic scale. This is the first study wherein the interaction between instantaneous dipole moment-induced PP and fillers is simulated and examined. The vdW interactions at the (hetero)interfaces are -59.66, -82.30, and -224.39 kJ mol Å for PP, calcium oxide (CaO; before carbonation), and calcium carbonate (CaCO; after carbonation), respectively, which provides concrete theoretical support for interesting findings such as the independence of tensile strength on filler loadings and "well-grown" interface-induced higher conductivity characteristics of the composites. Therefore, this work can offer practical solutions to mitigate pollution, provide a new perspective on fundamental physical interactions, and guide the development of practical next-generation composite materials.
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http://dx.doi.org/10.1016/j.jhazmat.2021.126725DOI Listing
July 2021

Gas chromatography-mass spectrometry analyses of encapsulated stable perovskite solar cells.

Science 2020 06 21;368(6497). Epub 2020 May 21.

Australian Centre for Advanced Photovoltaics, School of Photovoltaic and Renewable Energy Engineering, University of New South Wales, Sydney, NSW 2052, Australia.

Although perovskite solar cells have produced remarkable energy conversion efficiencies, they cannot become commercially viable without improvements in durability. We used gas chromatography-mass spectrometry (GC-MS) to reveal signature volatile products of the decomposition of organic hybrid perovskites under thermal stress. In addition, we were able to use GC-MS to confirm that a low-cost polymer/glass stack encapsulation is effective in suppressing such outgassing. Using such an encapsulation scheme, we produced multi-cation, multi-halide perovskite solar cells containing methylammonium that exceed the requirements of the International Electrotechnical Commission 61215:2016 standard by surviving more than 1800 hours of the Damp Heat test and 75 cycles of the Humidity Freeze test.
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http://dx.doi.org/10.1126/science.aba2412DOI Listing
June 2020

Study on the State Change of Ir/Al₂O₃ Catalyst by Decomposition of Ammonium Dinitramide (ADN) Based Low-Toxicity Monopropellant.

J Nanosci Nanotechnol 2020 09;20(9):5780-5782

Department of Aerospace Engineering, Chosun University, Dong-gu, Gwangju 61452, Republic of Korea.

The change of the Ir/Al₂O₃ catalyst before and after the reaction with ADN based low-toxicity monopropellant was confirmed. The catalyst were recovered after decomposition reaction with propellant in a monopropellant thruster at 350 °C preheating condition. Catalyst analysis was performed using a scanning electron microscope (SEM) and Brunauer-Emmett-Teller (BET) analyzer. The change of the catalyst specific devices.
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http://dx.doi.org/10.1166/jnn.2020.17642DOI Listing
September 2020

Unveiling the Relationship between the Perovskite Precursor Solution and the Resulting Device Performance.

J Am Chem Soc 2020 Apr 18;142(13):6251-6260. Epub 2020 Mar 18.

School of Energy and Chemical Engineering, Ulsan National Institute of Science and Technology (UNIST), 50 UNIST-gil, Eonyang-eup, Ulju-gun, Ulsan 44919, Republic of Korea.

For the fabrication of perovskite solar cells (PSCs) using a solution process, it is essential to understand the characteristics of the perovskite precursor solution to achieve high performance and reproducibility. The colloids (iodoplumbates) in the perovskite precursors under various conditions were investigated by UV-visible absorption, dynamic light scattering, photoluminescence, and total internal reflection fluorescence microscopy techniques. Their local structure was examined by in situ X-ray absorption fine structure studies. Perovskite thin films on a substrate with precursor solutions were characterized by transmission electron microscopy, X-ray diffraction analysis, space-charge-limited current, and Kelvin probe force microscopy. The colloidal properties of the perovskite precursor solutions were found to be directly correlated with the defect concentration and crystallinity of the perovskite film. This work provides guidelines for controlling perovskite films by varying the precursor solution, making it possible to use colloid-engineered lead halide perovskite layers to fabricate efficient PSCs.
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http://dx.doi.org/10.1021/jacs.0c00411DOI Listing
April 2020

A Novel Approach for the Development of Moisture Encapsulation Poly(vinyl alcohol--ethylene) for Perovskite Solar Cells.

ACS Omega 2019 May 24;4(5):9211-9218. Epub 2019 May 24.

Electronic Convergence Materials & Device Research Center, Korea Electronics Technology Institute (KETI), Seongnam-si, Gyeonggi-do 463-816, Republic of Korea.

In this study, we developed the universal encapsulation method using poly(vinyl alcohol--ethylene) (EVOH) to improve the water stability of perovskite solar cells. In order to enhance the moisture barrier property, we utilized SiO and graphene oxide (GO) fillers in the EVOH matrix. First, UV-treated SiO increased the dispersibility in the EVOH matrix and made the penetrating path more complicated, which led to a better moisture barrier property. The water vapor transmission ratio (WVTR) is enhanced from 4.72 × 10 (EVOH only) to 1.55 × 10 (EVOH with SiO filler) g/m day. Second, we found that GO reduce the unreacted hydroxyl groups that could attract water molecules at the surface of EVOH. The addition of GO increased the WVTR up to 3.34 × 10 g/m day. Finally, our EVOH-based film successfully encapsulated without the efficiency drop. The encapsulated devices surprisingly maintained 86% of their performance even under direct contact with water for 5 h.
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http://dx.doi.org/10.1021/acsomega.9b00350DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6648552PMC
May 2019

The Impact of a Dynamic Two-Step Solution Process on Film Formation of Cs (MA FA ) PbI Perovskite and Solar Cell Performance.

Small 2019 Mar 1;15(9):e1804858. Epub 2019 Feb 1.

Australian Centre for Advanced Photovoltaics (ACAP), School of Photovoltaic and Renewable and Engineering, University of New South Wales, Sydney, 2052, Australia.

This paper provides deep understanding of the formation mechanism of perovskite film fabricated by sequential solution-based methods. It compares two sequential spin-coating methods for Cs (MA FA ) PbI perovskite. First is the "static process," with a stoppage between the two spin-coating steps (1st PbI -CsI-dimethyl sulfoxide (DMSO)-dimethylformamide (DMF) and 2nd methylammonium iodide (MAI)-formamidinium iodide (FAI)-isopropyl alcohol). Second is the "dynamic process," where the 2nd precursor is dispensed while the substrate is still spinning from the 1st step. For the first time, such a dynamic process is used for Cs (MA FA ) PbI perovskite. Characterizations reveal improved film formation with the dynamic process due to the "retainment" of DMSO-complex necessary for the intermediate phase which i) promotes intercalation between precursors and ii) slows down perovskite crystallization for full conversion. The comparison on as-deposited perovskite before annealing indicates a more ordered film using this dynamic process. This results in a thicker, more uniform film with higher degree of preferred crystal orientation and higher carrier lifetime after annealing. Therefore, dynamic-processed devices present better performance repeatability, achieving a higher average efficiency of 17.0% compared to static ones (15.0%). The new insights provided by this work are important for perovskite solar cells processed sequentially as the process has greater flexibility in resolving solvent incompatibility, allowing separate optimizations and allowing different deposition methods.
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http://dx.doi.org/10.1002/smll.201804858DOI Listing
March 2019

Light- and bias-induced structural variations in metal halide perovskites.

Nat Commun 2019 01 25;10(1):444. Epub 2019 Jan 25.

School of Materials Science and Engineering, University of New South Wales, Sydney, NSW, 2052, Australia.

Organic-inorganic metal halide perovskites have gained considerable attention for next-generation photovoltaic cells due to rapid improvement in power conversion efficiencies. However, fundamental understanding of underlying mechanisms related to light- and bias-induced effects at the nanoscale is still required. Here, structural variations of the perovskites induced by light and bias are systematically investigated using scanning probe microscopy techniques. We show that periodically striped ferroelastic domains, spacing between 40 to 350 nm, exist within grains and can be modulated significantly under illumination as well as by electric bias. Williamson-Hall analysis of X-ray diffraction results shows that strain disorder is induced by these applied external stimuli. We show evidence that the structural emergence of domains can provide transfer pathways for holes to a hole transport layer with positive bias. Our findings point to potential origins of I-V hysteresis in halide perovskite solar cells.
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http://dx.doi.org/10.1038/s41467-019-08364-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6347646PMC
January 2019

Study on Endurance and Performance of Impregnated Ruthenium Catalyst for Thruster System.

J Nanosci Nanotechnol 2018 Feb;18(2):1263-1265

Department of Aerospace Engineering, Chosun University, 309 Pilmum-daero, Dong-gu, Gwangju 61452, South Korea.

Performance and endurance of the Ru catalyst were studied for nitrous oxide monopropellant thruster system. The thermal decomposition of N2O requires a considerably high temperature, which make it difficult to be utilized as a thruster propellant, while the propellant decomposition temperature can be reduced by using the catalyst through the decomposition reaction with the propellant. However, the catalyst used for the thruster was frequently exposed to high temperature and high-pressure environment. Therefore, the state change of the catalyst according to the thruster operation was analyzed. Characterization of catalyst used in the operation condition of the thruster was performed using FE-SEM and EDS. As a result, performance degradation was occurred due to the volatilization of Ru catalyst and reduction of the specific surface area according to the phase change of Al2O3.
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http://dx.doi.org/10.1166/jnn.2018.14916DOI Listing
February 2018

Accelerated Lifetime Testing of Organic-Inorganic Perovskite Solar Cells Encapsulated by Polyisobutylene.

ACS Appl Mater Interfaces 2017 Aug 24;9(30):25073-25081. Epub 2017 Jul 24.

The Australian Centre for Advanced Photovoltaics (ACAP), School of Photovoltaic and Renewable Energy Engineering, University of New South Wales , Sydney 2052, Australia.

Metal halide perovskite solar cells (PSCs) have undergone rapid progress. However, unstable performance caused by sensitivity to environmental moisture and high temperature is a major impediment to commercialization of PSCs. In the present work, a low-temperature, glass-glass encapsulation technique using high performance polyisobutylene (PIB) as the moisture barrier is investigated on planar glass/FTO/TiO/FAPbI/PTAA/gold perovskite solar cells. PIB was applied as either an edge seal or blanket layer. Electrical connections to the encapsulated PSCs were provided by either the FTO or Au layers. Results of a "calcium test" demonstrated that a PIB edge-seal effectively prevents moisture ingress. A shelf life test was performed and the PIB-sealed PSC was stable for at least 200 days. Damp heat and thermal cycling tests, in compliance with IEC61215:2016, were used to evaluate different encapsulation methods. Current-voltage measurements were performed regularly under simulated AM1.5G sunlight to monitor changes in PCE. The best results we have achieved to date maintained the initial efficiency after 540 h of damp heat testing and 200 thermal cycles. To the best of the authors' knowledge, these are among the best damp heat and thermal cycle test results for perovskite solar cells published to date. Given the modest performance of the cells (8% averaged from forward and reverse scans) especially with the more challenging FAPbI perovskite material tested in this work, it is envisaged that better stability results can be further achieved when higher performance perovskite solar cells are encapsulated using the PIB packaging techniques developed in this work. We propose that heat rather than moisture was the main cause of our PSC degradation. Furthermore, we propose that preventing the escape of volatile decomposition products from the perovskite solar cell materials is the key for stability. PIB encapsulation is a very promising packaging solution for perovskite solar cells, given its demonstrated effectiveness, ease of application, low application temperature, and low cost.
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http://dx.doi.org/10.1021/acsami.7b07625DOI Listing
August 2017

Bistable Solid-State Fluorescence Switching in Photoluminescent, Infinite Coordination Polymers.

Chemistry 2017 Jul 10;23(42):10017-10022. Epub 2017 Jul 10.

Center for Supramolecular Optoelectronic Materials and Department of Materials Science and Engineering, Seoul National University, Daehak-dong, Gwanak-gu, Seoul, Korea.

Photo-functional infinite coordinated polymers (ICPs) were synthesized that consist of the photochromic dithienylethene (DTE) and a luminescent bridging unit to give enhanced fluorescence in the solid state. We could fabricate well-ordered micropatterns of these ICPs by a soft-lithographic method, which repeatedly showed high contrast on-off fluorescence switching.
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http://dx.doi.org/10.1002/chem.201701656DOI Listing
July 2017

Acoustic-optical phonon up-conversion and hot-phonon bottleneck in lead-halide perovskites.

Nat Commun 2017 01 20;8:14120. Epub 2017 Jan 20.

Australian Centre for Advanced Photovoltaics, School of Photovoltaics and Renewable Energy Engineering, University of New South Wales, Sydney, New South Wales 2052, Australia.

The hot-phonon bottleneck effect in lead-halide perovskites (APbX) prolongs the cooling period of hot charge carriers, an effect that could be used in the next-generation photovoltaics devices. Using ultrafast optical characterization and first-principle calculations, four kinds of lead-halide perovskites (A=FA/MA/Cs, X=I/Br) are compared in this study to reveal the carrier-phonon dynamics within. Here we show a stronger phonon bottleneck effect in hybrid perovskites than in their inorganic counterparts. Compared with the caesium-based system, a 10 times slower carrier-phonon relaxation rate is observed in FAPbI. The up-conversion of low-energy phonons is proposed to be responsible for the bottleneck effect. The presence of organic cations introduces overlapping phonon branches and facilitates the up-transition of low-energy modes. The blocking of phonon propagation associated with an ultralow thermal conductivity of the material also increases the overall up-conversion efficiency. This result also suggests a new and general method for achieving long-lived hot carriers in materials.
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http://dx.doi.org/10.1038/ncomms14120DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5263885PMC
January 2017

Spectral dependence of direct and trap-mediated recombination processes in lead halide perovskites using time resolved microwave conductivity.

Phys Chem Chem Phys 2016 04;18(17):12043-9

School of Physics, UNSW, Sydney, NSW 2052, Australia.

Elucidating the decay mechanisms of photoexcited charge carriers is key to improving the efficiency of solar cells based on organo-lead halide perovskites. Here we investigate the spectral dependence (via above-, inter- and sub-bandgap optical excitations) of direct and trap-mediated decay processes in CH3NH3PbI3 using time resolved microwave conductivity (TRMC). We find that the total end-of-pulse mobility is excitation wavelength dependent - the mobility is maximized (172 cm(2) V(-1) s(-1)) when charge carriers are excited by near bandgap light (780 nm) in the low charge carrier density regime (10(9) photons per cm(2)), and is lower for above- and sub-bandgap excitations. Direct recombination is found to occur on the 100-400 ns timescale across excitation wavelengths near and above the bandgap, whereas indirect recombination processes displayed distinct behaviour following above- and sub-bandgap excitations, suggesting the influence of different trap distributions on recombination dynamics.
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http://dx.doi.org/10.1039/c5cp07360jDOI Listing
April 2016
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