• Title, Summary, Keyword: Photocathode

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Electrical Characteristics of Flat Cesium Antimonide Photocathode Emitters in Panel Devices

  • Jeong, Hyo-Soo
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.5
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    • pp.306-309
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    • 2016
  • The Cs3Sb photocathode was formed by non-vacuum process technology. An in-situ vacuum device was fabricated successively with flat cesium antimonide photocathode emitters fabricated in a process chamber. The electrical properties of the device were characterized. Electron emission from the devices was induced by photoemitted electrons, which were accelerated by an anode electric field that was shielded from the photoemitter surface. The electrical characteristics of the devices were investigated by measuring the anode current as a function of device operation times with respect to applied anode voltages. Planar blue LED light with a 450 nm wavelength was used as an excitation source. The results showed that the cesium antimonide photocathode emitter has the potential of long lifetime with stable electron emission characteristics in panel devices. These features demonstrate that the cesium antimony photocathodes produced by non-vacuum processing technology is suitable for flat cathodes in panel device applications.

Manufacturing of Cs3Sb Photocathode in Atmospheric Conditions

  • Jeong, Hyo-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.10
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    • pp.653-656
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    • 2014
  • $Cs_3Sb$ photocathode was formed by newly developed process and successive in-situ lighting devices were fabricated in a process chamber. R, G, and B phosphors were applied on the anode plate, respectively. Major parameters such as brightness, power consumption, and efficacy were measured. The wavelength of LED excitation source was 450 nm. Both high power and low power modes were applied in the measurement. Measurement values were clearly differentiated by the voltage application modes. The measured values of each parameter was good enough to be applied for general lighting source. The results showed that $Cs_3Sb$ photocathode formed in atmospheric conditions was functioning as good as the photocathode formed in UHV conditions, and thus it could be applied to advanced lighting devices.

A Study on Electron Emission Characteristics of Photocathode Formed Under Condition in N2 Atmosphere (상압에서 제조한 포토캐소드의 전자방출 특성에 관한 연구)

  • Jeong, Hyo-Soo
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.5
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    • pp.312-316
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    • 2014
  • Photoemission is a process in which photons are converted into free electrons. Photocathodes are the typical materials for the process. They emit electrons when a light is irradiated upon. The traditional method of manufacturing photocathodes is complicated, requires specialized equipment, and is limited very small sized samples. $Cs_3Sb$ photocathode was formed on a substrate in $N_2$ atmospheric conditions. The photocathode formation was a gas phase reaction with the substrate. Vacuum devices were made to test electron emission characteristics of the formed photocathode. Visible light of wavelength 475 nm was used for the primary light source. The results showed high current density and long term stability of the photoelectron emission.

Manufacturing of a Planar Lighting Device Using Cs3Sb Photocathode Emitters

  • Jeong, Hyo-Soo
    • Transactions on Electrical and Electronic Materials
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    • v.17 no.1
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    • pp.41-45
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    • 2016
  • The Cs3Sb photocathode was formed by non-vacuum process technology and successive in-situ photocathode vacuum device fabrication carried out in a process chamber. Performance testing of the device was followed. Light emission from the devices was induced by photoemitted electrons, which were accelerated by an anode electric field that was shielded from the photoemitter surface. The luminescent characteristics of the devices were investigated by measuring the optical parameters as functions of the applied anode voltages. The results showed that this approach could produce a more easily directed and controlled stream of light. These features make these devices suitable for a variety of planar lighting applications.

Carbon Nanotube Passivation layer for Increasing the Solar Water Splitting Performance of CdS/CuInGaSe Photocathode

  • Bae, Hyojung;Ko, Young-Hee;Park, Jun-Beom;Ko, Hang-Ju;Ryu, Sang-Wan;Ha, Jun-Seok
    • Journal of the Microelectronics and Packaging Society
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    • v.26 no.4
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    • pp.107-111
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    • 2019
  • We report the fabrication of a CdS/CuInGaSe (CdS/CIGS) structure with carbon nanotubes and its application as a photocathode for photoelectrochemical water splitting. CIGS thin films were fabricated using co-evaporation by RF magnetron sputtering, while CdS was fabricated by chemical bath deposition. Spray coated multi-wall carbon nanotube (CNT) film on CdS/CIGS thin film was investigated as a photocathode. The CNT-coated CdS/CIGS showed superior photocurrent density and exhibited improved photostability.

Fabrication and Electrical Characterization of Planar Lighting Devices with Cs3Sb Photocathode Emitters

  • Jeong, Hyo-Soo;Keller, Kris;Culkin, Brad
    • Journal of the Korean Physical Society
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    • v.70 no.6
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    • pp.610-614
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    • 2017
  • Non-vacuum process technology was used to produce $Cs_3Sb$ photocathodes on substrates, and insitu panel devices were fabricated. The performance of the devices was characterized by measuring the anode current as functions of the devices' operation times. An excitation light source with a 475-nm wavelength was used for the photocathodes. The device has a simple diode structure, providing unique characteristics such as a large gap, vertical electron beam directionality, and resistance to surface contamination from ion bombardment and poisoning by outgassing species. Accordingly, $Cs_3Sb$ photocathodes function as flat emitters, and the emission properties of the photocathode emitters depend on the vacuum level of the devices. An improved current stability has been observed after conducting an electrical conditioning process to remove possible adsorbates on the $Cs_3Sb$ flat emitters.

Fabrication and Photoelectrochemical Properties of a Cu2O/CuO Heterojunction Photoelectrode for Hydrogen Production from Solar Water Splitting (태양광 물 분해를 통한 수소 생산용 Cu2O/CuO 이종접합 광전극의 제작 및 광전기화학적 특성)

  • Kim, Soyoung;Kim, Hyojin;Hong, Soon-Ku;Kim, Dojin
    • Korean Journal of Materials Research
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    • v.26 no.11
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    • pp.604-610
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    • 2016
  • We report on the fabrication and characterization of a novel $Cu_2O/CuO$ heterojunction structure with CuO nanorods embedded in $Cu_2O$ thin film as an efficient photocathode for photoelectrochemical (PEC) solar water splitting. A CuO nanorod array was first prepared on an indium-tin-oxide-coated glass substrate via a seed-mediated hydrothermal synthesis method; then, a $Cu_2O$ thin film was electrodeposited onto the CuO nanorod array to form an oxide semiconductor heterostructure. The crystalline phases and morphologies of the heterojunction materials were examined using X-ray diffraction and scanning electron microscopy, as well as Raman scattering. The PEC properties of the fabricated $Cu_2O/CuO$ heterojunction photocathode were evaluated by photocurrent conversion efficiency measurements under white light illumination. From the observed PEC current density versus voltage (J-V) behavior, the $Cu_2O/CuO$ photocathode was found to exhibit negligible dark current and high photocurrent density, e.g. $-1.05mA/cm^2$ at -0.6 V vs. $Hg/HgCl_2$ in $1mM\;Na_2SO_4$ electrolyte, revealing the effective operation of the oxide heterostructure. The photocurrent conversion efficiency of the $Cu_2O/CuO$ photocathode was estimated to be 1.27% at -0.6 V vs. $Hg/HgCl_2$. Moreover, the PEC current density versus time (J-T) profile measured at -0.5 V vs. $Hg/HgCl_2$ on the $Cu_2O/CuO$ photocathode indicated a 3-fold increase in the photocurrent density compared to that of a simple $Cu_2O$ thin film photocathode. The improved PEC performance was attributed to a certain synergistic effect of the bilayer heterostructure on the light absorption and electron-hole recombination processes.

Expanding depletion region via doping: Zn-doped Cu2O buffer layer in Cu2O photocathodes for photoelectrochemical water splitting

  • Lee, Kangha;Lee, Cheol-Ho;Cheong, Jun Young;Lee, Seokwon;Kim, Il-Doo;Joh, Han-Ik;Lee, Doh Chang
    • Korean Journal of Chemical Engineering
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    • v.34 no.12
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    • pp.3214-3219
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    • 2017
  • We report photoelectrochemical hydrogen evolution reaction using a $Cu_2O$-based photocathode with a layer doped with Zn ions. The doping results in the shift of the onset flat-band potential of the photocathode, likely a consequence of maximized band-bending in the $Cu_2O/Zn$ : $Cu_2O$ heterojunction. Systematic electrochemical analysis reveals that expansion of depletion region is responsible for the enhanced photoelectrochemical performance, e.g., the increase of photocurrent and reduced internal resistance.

Photoelectrochemical Properties of Electrodeposited Cu2O Photocathode with Tailored Microstructures (미세구조가 제어된 전해도금 Cu2O 광양극의 광전기화학 특성)

  • Jeong, Dasol;Jo, Woohyeon;Jeong, Jaebum;Jung, Hyunsung
    • Journal of the Korean institute of surface engineering
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    • v.53 no.5
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    • pp.232-240
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    • 2020
  • Cu2O films as a photocathode for photoelectrochemical water splitting were potentiostatically deposited on FTO glasses. The morphology and composition of the electrodeposited Cu2O films were adjusted by the applied potentials. The potential-dependent grain size of Cu2O films was characterized by XRD and SEM analysis. Photoelectrochemical properties of the fabricated Cu2O photocathodes were investigated with photocurrents as a function of potentials under 1 sun condition of 100mW/㎠. Photocurrents of the electrodeposited Cu2O films were controlled with the tailored surface morphologies of Cu2O photocathodes.

Fabrication of a Planar UV Lighting Device Utilizing Cs3Sb Photocathode Emitters

  • Jeong, Hyo-Soo
    • Journal of the Korean Physical Society
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    • v.71 no.12
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    • pp.993-996
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    • 2017
  • Planar ultraviolet (UV) light sources with uniform intensity are ideal for UV treatments. A newly conceived planar UV lighting device utilizing $Cs_3Sb$ mono-alkali antimonide photocathodes as flat electron emitters is presented and analyzed here. The design concept involves a panel device that utilizes photocathodes operated in a reflection mode with an external excitation light source. The excitation light source is in the blue visible light range. Commercially available UV phosphors are used as a light source of desirable UV wavelengths. The light emission characteristics of the device are investigated by measuring the optical parameters as function of applied anode voltage. The UV light emission shows that cold UV light with the spectral characteristics of near-monochromatic distribution are most effective. It also demonstrates that the UV intensity is sufficient for the UV treatment. More importantly, the planar UV lighting device is mercury free. These make them suitable for all UV applications.