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Elongated Lifetime and Enhanced Flux of Hot Electrons on a Perovskite Plasmonic Nanodiode
Park, Yujin,Choi, Jungkweon,Lee, Changhwan,Cho, An-Na,Cho, Dae Won,Park, Nam-Gyu,Ihee, Hyotcherl,Park, Jeong Young American Chemical Society 2019 NANO LETTERS Vol.19 No.8
<P>A fundamental understanding of hot electron transport is critical for developing efficient hot-carrier-based solar cells. There have been significant efforts to enhance hot electron flux, and it has been found that a key factor affecting the hot electron flux is the lifetime of the hot electrons. Here, we report a combined study of hot electron flux and the lifetime of hot carriers using a perovskite-modified plasmonic nanodiode. We found that perovskite deposition on a plasmonic nanodiode can considerably improve hot electron generation induced by photon absorption. The perovskite plasmonic nanodiode consists of MAPbI<SUB>3</SUB> layers covering a plasmonic-Au/TiO<SUB>2</SUB> Schottky junction that is composed of randomly connected Au nanoislands deposited on a TiO<SUB>2</SUB> layer. The measured incident photon-to-electron conversion efficiency and the short-circuit photocurrent show a significantly improved solar-to-electrical conversion performance of this nanodiode. Such an improvement is ascribed to the improved hot electron flux in MAPbI<SUB>3</SUB> caused by effective light absorption from near-field enhancement of plasmonic Au and the efficient capture of hot electrons from Au nanoislands via the formation of a three-dimensional Schottky interface. The relation between the lifetime and flux of hot electrons was confirmed by femtosecond transient absorption spectroscopy that showed considerably longer hot electron lifetimes in MAPbI<SUB>3</SUB> combined with the plasmonic Au structure. These findings can provide a fundamental understanding of hot electron generation and transport in perovskite, which can provide helpful guidance to designing efficient hot carrier photovoltaics.</P> [FIG OMISSION]</BR>
Yujin Seong,Dami Yim,Min Ji Jang,Jeong Min Park,Seong Jin Park,Hyoung Seop Kim 대한금속·재료학회 2020 METALS AND MATERIALS International Vol.26 No.2
A physics-based constitutive model of porous materials is proposed to enhance the accuracy of numerical analysis in die/isostatic compaction. The correlation between the yield function and equivalent work equation was derived, and the numericalintegration method was modifed with the correlation. It is found that the apparent work of porous materials is lower than theproduct of relative density and equivalent work of solid materials at the beginning of compaction, implying the kinematicmotion of powders and the resultant particle rearrangement. For verifcation of the proposed model, fnite element analyseswere performed for the die/isostatic compaction of three metal powders: Ti, SUS316L, and Al6061 powders. Compared withtwo conventional constitutive models, the proposed model improves the accuracy of the densifcation behaviors in all thestage during die/isostatic compaction. Furthermore, this study is a groundwork to link the densifcation behavior of porousmaterials at bulk scale to the particulate behavior of powders at microscale.
Park, Sanghun,You, Jeongyeop,Ahn, Yujin,Jung, Woonggyu,Kim, Jihye,Lee, Sungyun,Park, Jongkwan,Cho, Kyung Hwa Elsevier 2018 Journal of membrane science Vol.548 No.-
<P><B>Abstract</B></P> <P>We studied the influence of bioavailability of organic matter on membrane fouling layer development by comparing the filtration performance of two feed waters (wetland water and graywater). Dissolved organic carbon (DOC) concentration, size exclusion chromatography (SEC), and fluorescence excitation-emission matrix (FEEM) were used to characterize the bioavailability of organic matter in these water samples during the nanofiltration process. The wetland sample contained a high proportion of humic acid- and fulvic acid-like matter with low bioavailability, whereas the graywater sample comprised substantial amounts of aromatic proteins and microbial byproduct-like matter with high bioavailability. In addition, the molecular size distribution revealed that the wetland sample contained a large portion of recalcitrant organic matter, whereas the graywater sample contained easily bioavailable organic matter. After the filtration experiment, the DOC of the wetland sample decreased to 4.8mgC/L, whereas the graywater sample resulted in a lower DOC concentration of 3.4mgC/L. Optical coherence tomography (OCT) illustrated real-time variations in the fouling layer morphology, providing both 2D and 3D images. In addition, confocal laser scanning microscopy (CLSM) quantified the bacterial volume in the fouling layer. The wetland sample yielded a bacterial volume of 11.8µm<SUP>3</SUP>/μm<SUP>2</SUP> from a total fouling volume of 103µm<SUP>3</SUP>/μm<SUP>2</SUP>, whereas the graywater sample yielded a bacterial volume of 53.2µm<SUP>3</SUP>/μm<SUP>2</SUP> from a total fouling layer volume of 134µm<SUP>3</SUP>/μm<SUP>2</SUP>. Fitting of the two-phase Monod model to the fouling layer growth on the membrane resulted in lower-yield coefficients (i.e., the volumes produced per unit amount of substrate, <SUB> Y xs </SUB> ) of 7.46 and 27.95µm<SUP>3</SUP>/μm<SUP>2</SUP> in wetland water and higher-yield coefficients of 13.17 and 47.53µm<SUP>3</SUP>/μm<SUP>2</SUP> in the graywater at first and second phase, respectively. This study addresses the quantitative evaluation of the organic matter bioavailability in terms of membrane fouling using OCT images and a two-phase Monod model.</P> <P><B>Highlights</B></P> <P> <UL> <LI> The difference of bioavailability of DOM influenced the amount of fouling layer growth. </LI> <LI> In situ OCT monitoring provided 2D and 3D morphology of the fouling layer and quantified the volume. </LI> <LI> Two-phase Monod model evaluated the influence of bioavailability of DOM on fouling layer growth. </LI> </UL> </P>