• Title/Summary/Keyword: Photocathode

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Photoelectrochemical Hydrogen Production on Textured Silicon Photocathode

  • Oh, Il-Whan
    • Journal of the Korean Electrochemical Society
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    • v.14 no.4
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    • pp.191-195
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    • 2011
  • Wet chemical etching methods were utilized to conduct Si surface texturing, which could enhance photoelectrochemical hydrogen generation rate. Two different etching methods tested, which were anisotropic metal-catalyzed electroless etching and isotropic etching. The Si nano-texture that was fabricated by the anisotropic etching showed ~25% increase in photocurrent for H2 generation. The photocurrent enhancement was attributed to the reduced reflection loss at the nano-textured Si surface, which provided a layer of intermediate density between water and the Si substrate.

Vacuum system for PAL-XFEL (4세대방사광가속기 진공시스템)

  • Na, Donghyun
    • Vacuum Magazine
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    • v.4 no.1
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    • pp.12-15
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    • 2017
  • The Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) is a 0.1 nm hard X-ray FEL which aims at providing photon flux higher than $1{\times}10^{12}$ photons/pulse using a 10-GeV electron linac. The vacuum system of the machine consists of an injector section including an S-band photocathode RF gun, 10-GeV electron linac section based on S-band normal conducting accelerating structures and a 150-m long out-vacuum undulator system. We introduce the present status of PAL-XFEL vacuum systems.

Simple fabrication route for vertically-aligned CZTS nanorod arrays for photoelectrochemical application based on AAO template

  • Kim, Ji-Min;Yang, U-Seok;O, Yun-Jeong;Mun, Ju-Ho
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.402.2-402.2
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    • 2016
  • In photoelectrochemical (PEC) water splitting, Cu2ZnSnS4 (CZTS) compound has attracted intense attention as a photocathode due to not only large optical absorption coefficient, but also earth-abundance of constituent elements and suitable band alignment. With rapid development of nanotechnology, one-dimensional nanostructures of CZTS have been investigated as a potential form to achieve high efficiency because the nanostructures are expected to be capable of capturing more light and enhancing charge separation and transport. Here, we report a well-controlled fabrication route for vertically-aligned CZTS nanorod arrays on anodic aluminium oxide (AAO) template via simple sol-gel process followed by deposition of ZnS or CdS buffer layers on the CZTS nanorod to enhance charge separation. The structure, morphology, composition, optical absorption, and PEC properties of the resulting CZTS nanorod samples were characterized using X-ray diffraction, Raman spectroscopy, transmission electron microscopy, energy dispersive X-ray spectrometry, scanning electron microscopy, and UV-vis spectroscopy.

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Photoelectrochemical characterization of surface-modified CuInS2 nanorod arrays prepared via template-assisted growth and transfer

  • Yang, Wooseok;Kim, Jimin;Oh, Yunjung;Moon, Jooho
    • Proceedings of the Korean Vacuum Society Conference
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    • 2016.02a
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    • pp.401-401
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    • 2016
  • Although vertically aligned one-dimensional (1D) structure has been considered as efficient forms for photoelectrode, development of efficient 1D nanostructured photocathode are still required. In this sense, we recently demonstrated a simple fabrication route for CuInS2 (CIS) nanorod arrays from aqueous solution by template-assisted growth-and-transfer method and their feasibility as a photoelectrode for water splitting. In this study, we further evaluated the photoelectrochemical properties surface-modified CIS nanorod arrays. Surface modification with CdS and ZnS was performed by successive ion layer adsorption and reaction (SILAR) method, which is well known as suitable technique for conformal coating throughout nanoporous structure. With surface modification of CdS and ZnS, both photoelectrochemical performance and stability of CuInS2 nanorod arrays were improved by shifting of the flat-band potential, which was analyzed both onset potential and Mott-schottky plot.

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Photovoltaic Effects of the p$\cdot$Si-Electrolyte Junction (p$\cdot$Si-전해질 접합의 광기전력 효과)

  • Han, Seok-Yong;Kim, Yeon-Hui;Kim, Hwa-Taek
    • Journal of the Korean Institute of Telematics and Electronics
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    • v.19 no.6
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    • pp.52-54
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    • 1982
  • p·Si-전해질 접합을 전해질로 6N H2SO4, 6N H2SO4(Ti3+), 6N H2SO4(Ti4+), 6N H2SO4(Ti4+/Ti3+)을 사용하여 만들었다. 이들 전해질중 6N H2SO4(Ti4-/Ti3+)을 사용할 때 p·Si 광음극이 안정하게 동학하며 높은 광전 감도를 가지고 있었다. p·Si-electrolyte junction are prepared by using p·Si photocatode in four different electrolytes such as 6N H2SO4, 6N H2SO4(Ti3+), 6N H2SO4(Ti4+), 6N H2SO4(Ti4+/Ti3+) respectively. Among those electrolytes 6N H2SO4(Ti4-/Ti3+) shows very good results, in which p·Si photocathode is stable.

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Operating Characteristics of a Time-Correlated Single Photon Counting System and its Application to Fluorescence Life Time Measurements (시간 상관 단일 광자 계수기의 동작 특성과 형광 수명 시간 측정에의 응용)

  • Ko, D.S.;Jung, H.S.;Kim, U.
    • Proceedings of the KIEE Conference
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    • 1989.11a
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    • pp.512-514
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    • 1989
  • A time-correlated single photon counting system combined with a mode locked $Ar^+$ laser has been utilized to measure the fluorescence decay. A side-on type photomultiplier tube has been used as a photon detector. By restricting the sensitive area and the position of the photocathode, the transit time differencies of photoelectrons in PMT has been reduced. The fluorescence life time of rhodamin 6G in ethylene glycol measured 3.9$\pm$10 ns.

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DESIGNING A SMALL-SIZED ENGINEERING MODEL OF SOLAR EUV TELESCOPE FOR A KOREAN SATELLITE (인공위성 탑재용 소형 극자외선 태양망원경 공학 모형 설계)

  • 한정훈;장민환;김상준
    • Journal of Astronomy and Space Sciences
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    • v.18 no.2
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    • pp.145-152
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    • 2001
  • For the research of solar EUV (extreme ultraviolet) radiation, we have designed a small-sifted engineering model of solar EUV telescope, which is suitable for a Korean satellite. The EUV sole. telescope was designed to observe the sun at $584.3AA$(He I) and $629.7AA$(OV) The optical system is an f/8 Ritchey-Chr rien, and the effective diameter and focal length are 80mm and 640mm, respectively. The He I and 0V filters are loaded in a filter wheel. In the detection part, the MCP (Microchannel Plate) type is Z-stack, and the channel-to-diameter radio is 40:1. MCP and CCD are connected by fiber optic taper. A commercial optical design software is used for the analysis of the optical system design.

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Photoelectrochemical Water Splitting on a Delafossite CuGaO2 Semiconductor Electrode

  • Lee, Myeongsoon;Kim, Don;Yoon, Yong Tae;Kim, Yeong Il
    • Bulletin of the Korean Chemical Society
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    • v.35 no.11
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    • pp.3261-3266
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    • 2014
  • A pellet of polycrystalline $CuGaO_2$ with a delafossite structure was prepared from $Ga_2O_3$ and CuO by high-temperature solid-state synthesis. The $CuGaO_2$ pellet was a p-type semiconductor for which the electrical conductivity, carrier density, carrier mobility and Seebeck coefficient were $5.34{\times}10^{-2}{\Omega}^{-1}cm^{-1}$, $3.5{\times}10^{20}cm^{-3}$, $9.5{\times}10^{-4}cm^2V^{-1}s^{-1}$ at room temperature, and $+360{\mu}V/K$, respectively. It also exhibited two optical transitions at about 2.7 and 3.6 eV. The photoelectrochemical properties of the $CuGaO_2$ pellet electrode were investigated in aqueous electrolyte solutions. The flat-band potential of this electrode, determined using a Mott-Schottky plot, was +0.18 V vs SCE at pH 4.8 and followed the Nernst equation with respect to pH. Under UV light illumination, a cathodic photocurrent developed, and molecular hydrogen simultaneously evolved on the surface of the electrode due to the direct reduction of water without deposition of any metal catalyst.

A Study on the Possibility of Dye Wastewater Treatment of Electrical Photocatalytic System Using TiO2 nanotube plate (TiO2 nanotube plate를 이용한 전기적광촉매시스템의 염료폐수 처리 가능성 연구)

  • Lee, Yongho;Sun, Minghao;Pak, Daewon
    • Journal of Korean Society on Water Environment
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    • v.35 no.5
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    • pp.418-424
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    • 2019
  • In this study, $TiO_2$ nanotubes with different morphologies were prepared in the electrolyte consisting of ethylene glycol, ammonium fluoride($NH_4F$), and deionized water($H_2O$) by controlling the voltage and time in the anodization method. Thicknesses and pore sizes of these $TiO_2$ nanotubes were measured to interpret the relationship between anodization conditions and $TiO_2$ nanotube morphologies. Element contents in the $TiO_2$ nanotubes were detected for further analysis of $TiO_2$ nanotube characteristics. Photoelectrolyticdecolorization efficiencies of the $TiO_2$ nanotube plates with various morphologies were tested to clarify the morphology that a highly active $TiO_2$ nanotube plate should have. Influences of applied voltage in photoelectrolysis processes and sodium sulfate($Na_2SO_4$) concentration in wastewater on the decolorization efficiency were also studied. To save the equipment investment cost in photoelectrolysis methods, a two-photoelectrode system that uses the $TiO_2$ nanotube plates as photoanode and photocathode instead of adding other counter electrodes was studied. Compared with single-photoelectrode system that uses the $TiO_2$ nanotube plate as photoanode and titanium plate as cathode on the view of the treatment of dye wastewater containing different amounts of salt. As a result, a considerably suitable voltage was strictly needed for enhancing the photoelectrolyticdecolorization effect of the two-photoelectrode system but if salts exist in wastewater, an excellent increase in the decolorization efficiency can be obtained.

Growth of GaAs/AlGaAs structure for photoelectric cathode (광전음극 소자용 GaAs/AlGaAs 구조의 LPE 성장)

  • Bae, Sung Geun;Jeon, Injun;Kim, Kyoung Hwa
    • Journal of the Korean Crystal Growth and Crystal Technology
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    • v.27 no.6
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    • pp.282-288
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    • 2017
  • In this paper, GaAs/AlGaAs multi-layer structure was grown by liquid phase epitaxy with graphite sliding boat, which can be used as a device structure of a photocathode image sensor. The multi-layer structure was grown on an n-type GaAs substrate in the sequence as follows: GaAs buffer layer, Zn-doped p-type AlGaAs layer as etching stop layer, Zn-doped p-type GaAs layer, and Zn-doped p-type AlGaAs layer. The Characteristics of GaAs/AlGaAs structures were analyzed by using scanning electron microscope (SEM), secondary ion mass spectrometer (SIMS) and hall measurement. The SEM images shows that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure was grown with a mirror-like surface on a whole ($1.25mm{\times}25mm$) substrate. The Al composition in the AlGaAs layer was approximately 80 %. Also, it was confirmed that the free carrier concentration in the p-GaAs layer can be adjusted to the range of $8{\times}10^{18}/cm^2$ by hall measurement. In the result, it is expected that the p-AlGaAs/p-GaAs/p-AlGaAs multi-layer structure grown by the LPE can be used as a device structure of a photoelectric cathode image sensor.