• Korean Journal of Soil Science and Fertilizer
• /
• v.46 no.6
• /
• pp.659-664
• /
• 2013

The aim of this study is to determine the drought stress index through photochemical analysis in red pepper (Capsiumannuum L.). The photochemical interpretation was performed in the basis of the relation between Kautsky effect and Photosystem II (PSII) following the measurement of chlorophyll, pheophytin contents, and $CO_2$ assimilation in drought stressed 5-week-old red pepper plants. The $CO_2$ assimilation rate was severely lowered with almost 77% reduction of chlorophyll and pheophytin contents at four days after non-irrigation. It was clearly observed that the chlorophyll fluorescence intensity rose from a minimum level (the O level), in less than one second, to a maximum level (the P-level) via two intermediate steps labeled J and I (OJIP process). Drought factor index (DFI) was also calculated using measured OJIP parameters. The DFI was -0.22, meaning not only the initial inhibition of PSII but also sequential inhibition of PSI. In real, most of all photochemical parameters such as quantum yield of the electron transport flux from Quinone A ($Q_A$) to Quinone B ($Q_B$), quantum yield of the electron transport flux until the PSI electron acceptors, quantum yield of the electron transport flux until the PSI electron acceptors, average absorbed photon flux per PSII reaction center, and electron transport flux until PSI acceptors per cross section were profoundly reduced except number of QA reducing reaction centers (RCs) per PSII antenna chlorophyll (RC/ABS). It was illuminated that at least 6 parameters related with quantum yield/efficiency and specific energy fluxes (per active PSII RC) could be applied to be used as the drought stress index. Furthermore, in the combination of parameters, driving forces (DF) for photochemical activity could be deduced from the performance index (PI) for energy conservation from photons absorbed by PSII antenna until the reduction of PSI acceptors. In conclusion, photochemical responses and their related parameters can be used as physiological DFI.

• Journal of Ginseng Research
• /
• v.14 no.2
• /
• pp.135-141
• /
• 1990

In order to elucidate the mechanism of the leaf-burning disease of ginseng (Panax ginseng C.A. Meyer), the relationships between thylakoid membrane peroxidation and chlorophyll bleaching were investigated in comparison with the ones of soybean (Glycine max L). When I measured the rate of lipid peroxidation in the thylakoids of ginseng and soybean by irradiation of light(60 w.m-2), it was identified that, the remarkably lower rate of lipid peroxidation was found in the ginseng thylakoid than the case of soybean. When lipid peroxidation of ginseng thylakoid was induced in the dark, chlorophyll contents of thylakoid was not changed. The results suggest that lipid peroxidation does not affect the chlorophyll bleaching in ginseng thylakoid. Thylakoid membrane peroxidation as well as chlorophyll bleaching was closely related with photosynthetic electron transport. But, according to the quenching experiment active oxygen species induced lipid peroxidation may be different species in the case of chlorophyll bleaching.

• Journal of Plant Biology
• /
• v.37 no.2
• /
• pp.231-236
• /
• 1994

The effect of $Cd^{2+}$ on the electron transport rate of PSI and PSII was investigated in isolated spinach chloroplasts. In photosystem II, the rate of electron transport was decreased as the concentration of $Cd^{2+}$ was increased from 1 to $100\;\mu\textrm{M}$. The inhibitory effect of $Cd^{2+}$ was reduced when diphenylcarbazide was added to the reaction medium, indicating that $Cd^{2+}$ affects primarily psn oxygen evolving complexes of thylakoid membrane. The inhibitory effect of $Cd^{2+}$ was reduced when $Mn^{2+}\;and\;Ca^{2+}$ were added to the reaction medium, but the inhibitory effect was not fully relieved. Although the activity of psn was decreased significantly by the treatment of $50\;\mu\textrm{M}\;Cd^{2+}$, Fv/Fm was decreased slightly. However, the treatment of $100\;\mu\textrm{M}\;Cd^{2+}$ resulted in the marked decrease of Fv/Fm. In photosystem I, the rate of electron transport decreased as the concentration of $Cd^{2+}$ was increased from 0.2 to 3.2 mM. The inhibitory effect of $Cd^{2+}$ was decreased when the chloroplast treated with $Cd^{2+}$ was washed by centrifugation.gation.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.150.2-150.2
• /
• 2015

In this study, we analyzed the electric and optical characteristics by using various deposition rate ($0.5{\AA}$, $1.0{\AA}$ and $1.5{\AA}/s$) in order to enhance the performance in organic light-emitting devices (OLED). The organic multi-layer structures were deposited with NPB ($500{\AA}$ as hole transport layer), Alq3 ($600{\AA}$ as electron transport layer and emission layer) and LiF ($8{\AA}$ as electron injection layer) via SUNIC PLUS200 on Glass/ITO substrates. In this experiment, we examined the relationship between porous state of organic deposition and mobility of the organic materials. Among the three deposition rates, $0.5{\AA}/s$ achieved the highest performance of (10,786cd/m2, 4.387cd/A) comparing with that of $1{\AA}/s$ (7,779cd/m2, 3.281cd/A) and $1.5{\AA}/s$ (5,167cd/m2, 2.693cd/A). We confirmed that low deposition rate helps to arrange organic materials densely and to move easily another atomic location using inter-chain transporting by orbital overlap.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.2
• /
• pp.670-674
• /
• 2012

The photovoltaic performance of solid-state dye-sensitized solar cells employing hole transport material (HTM), 2,2',7,7'-tetrakis-(N,N-di-p-methoxyphenyl-amine)-9,9'-spirobifluorene (spiro-MeOTAD), has been investigated in terms of HTM overlayer thickness. Two important parameters, soak time and spin-coating rate, are varied to control the HTM thickness. Decrease in the period of loading the spiro-MeOTAD solution on $TiO_2$ layer (soak time) leads to decrease in the HTM overlayer thickness, whereas decrease in spin-coating rate increases the HTM overlayer thickness. Photocurrent density and fill factor increase with decreasing the overlayer thickness, whereas open-circuit voltage remains almost unchanged. The improved photocurrent density is mainly ascribed to the enhanced charge transport rate, associated with the improved charge collection efficiency. Among the studied HTM overlayer thicknesses, ca. 230 nm-thick HTM overlayer demonstrates best efficiency of 4.5% at AM 1.5G one sun light intensity.

• Transactions on Electrical and Electronic Materials
• /
• v.18 no.2
• /
• pp.89-92
• /
• 2017

The performance of three-layered organic light-emitting diodes (OLEDs) was investigated using TPD hole-transport and injection layers, Teflon-AF, and the electron-injection layer of $Li_2CO_3$ and LiF. The OLEDs were manufactured in a structure of TPD/$Alq_3$/LiF, TPD/$Alq_3$/$Li_2CO_3$, and AF/$Alq_3$/LiF using low-molecular organic materials. In three different three-layered OLEDs, it was found that the device with the TPD/$Alq_3$/LiF structure shows higher performance in maximum luminance, and maximum external quantum efficiency compared to those of the device with TPD/$Alq_3$/$Li_2CO_3$ and TPD/$Alq_3$/LiF by 35% and 17%, and 193% and 133%, respectively. It is thought that the combined LiF/Al cathode contributes to a reduced work function and improves an electrical conduction mechanism due to the electron injection rather than the hole transport, which then increases a recombination rate of charge carriers.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2010.08a
• /
• pp.311-312
• /
• 2010

The fabricated photovoltaic cells based on PIN heterojunctions, in this study, have a structure of ITO/poly(3, 4-ethylenedioxythiophene)-poly(styrenesulfonate)(PEDOT:PSS)/donor/donor:C60(10nm)/C60(35nm)/2, 9-dimethyl-4, 7-diphenyl-1, 10-phenanthroline(8nm)/Al(100nm). The thicknesses of an active layer(donor:C60), an electron transport layer(C60), and hole/exciton blocking layer(BCP) were fixed in the organic photovoltaic cells. We investigated the performance characteristics of the PIN organic photovoltaic cells with copper phthalocyanine(CuPc), tetracene and pentacene as a hole transport layer. Discussion on the photovoltaic cells with CuPc, tetracene and pentacene as a hole transport layer is focussed on the dependency of the power conversion efficiency on the deposition rate and thickness of hole transport layer. The device performance characteristics are elucidated from open-circuit-voltage(Voc), short-circuit-current(Jsc), fill factor(FF), and power conversion efficiency($\eta$). As the deposition rate of donor is reduced, the power conversion efficiency is enhanced by increased short-circuit-current(Jsc). The CuPc-based PIN photovoltaic cell has the limited dependency of power conversion efficiency on the thickness of hole transport layer because of relatively short exciton diffusion length. The photovoltaic cell using tetracene as a hole transport layer, which has relatively long diffusion length, has low efficiency. The maximum power conversion efficiencies of CuPc, tetracene, and pentacene-based photovoltaic cells with optimized deposition rate and thickness of hole transport layer have been achieved to 1.63%, 1.33% and 2.15%, respectively. The photovoltaic cell using pentacene as a hole transport layer showed the highest efficiency because of dramatically enhanced Jsc due to long diffusion length and strong thickness dependence.

• Journal of Plant Biology
• /
• v.36 no.4
• /
• pp.313-319
• /
• 1993

Photoproduction of hydrogen by free and polyvinylalcohol (PVA)-immobilized spinach chloroplasts was investigated. Immobilization of chloroplast with PVA increased the functional stability of the chloroplast during storage. PVA-immobilized chloroplasts preserved photosynthetic electron transport activity much better than free chloroplasts. The hydrogen production of free chloroplast decreased to 17% of initial activity after storage of six days. The hydrogen production of the PVA-immobilized chloroplast, however, showed 44% of initial activity after storage of 15 days. The maximal rate of hydrogen production was accomplished at 2$^{\circ}C$ under the light intensity above 116 $\mu$E.m-2.s-1. The amount of hydrogen produced was proportional to the chlorophyll concentration. The hydrogen production was inhibited by DCMU treatment, indicating hydrogen production is dependent on photosynthetic electron transport. These results suggest that PVA is a good candidate for the immobilization matrix of chloroplasts for the photoproduction of hydrogen.

• Proceedings of the KIEE Conference
• /
• 1990.07a
• /
• pp.257-260
• /
• 1990

Monte Carlo simulations of electron impact ionization in silicon utilizing simple spherical band approximation including L valley are presented. The mean energy of electron at high electric field is lowered and the threshold energy of electron impact ionizaiotn is smeared out to $E_x$ by including L valley. This work also presents the importance of the modeling of L valley by calculating the electron population rate of it over the threshold energy of eletron impact ionization, which is higher than 10%

• Journal of the Korean Graphic Arts Communication Society
• /
• v.11 no.1
• /
• pp.103-122
• /
• 1993

A cause and counterplan of the increase in dark decay rate of$\varepsilon$-CuPc/PVCz photoreceptor which is consist of the carrier generation layer (CGL) of$\varepsilon$type copper phthalocyanine ($\varepsilon$-CuPc) thin film by an aqueous coating method and the carrier transport layer (CTL) of polyvinylcarbazol (PVCz) by spin coating, are studied in this paper. Electrochemical deposition of CGL was accompanied by an increase in work function of the aluminium substrate during the processes and the enhanced work function 5.3 eV rose above the ionization potential 5.16 eV of $\varepsilon$-CuPc. This resulted in the increased injection of holes from substrate into CGL and a fast dark decay rate. Improved photoreceptor, an electron-transport $\varepsilon$-CuPc/TNF photoreceptor, led to lowing of dark decay rate and increasing of photosensitivity. The carrier generation efficiency (ηg), carrier injection efficiency (ηi) and xerographic gain (G) of the $\varepsilon$-CuPc/TNF photoreceptor were obtained by XTOF method and PIDC.