• Title, Summary, Keyword: Photo current

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Fabrication and Characterization of Photo-Sensors for Very Small Scale Image System (초소형 영상시스템을 위한 광센서 제조 및 특성평가)

  • Shin, K.S.;Paek, K.K.;Lee, Y.S.;Lee, Y.H.;Park, J.H.;Ju, B.K.
    • Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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    • pp.187-190
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    • 2000
  • We fabricated general photo diode, surface etched photo diode and floating gate MOSFET by CMOS process. In a design stage, we expect that surface etched photo diode will be improved as to photo sensitivity. However, because the surface of silicon was damaged in etching process, the surface etched diode had a high dark current as well as low photo current level. Finally, we examined the current-voltage properties for the floating gate MOSFET on n-well and confirmed that the device can be act as an efficient photo-sensor. The floating gate MOSFET was operated in parasitic bipolar transistor mode.

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DSSCs Efficiencies of Photo Electrode Thickness and Modified Photo Electrode Surface Area (광전극 두께와 표면적 변형에 따른 DSSC의 효율 특성)

  • Kwon, Sung-Yeol;Yang, Wook;Zhou, Ze-Yuan
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.27 no.2
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    • pp.115-120
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    • 2014
  • Photo electrode is an important component for DSSC. DSSCs electrical characteristics and efficiencies fabricated with different $TiO_2$ photo electrodes thickness and modified phoro electrode surface area were studied. $11{\mu}m$ $TiO_2$ photo electrode shows a 4.956% efficiency. The highest short circuit current density was a $9.949mA/cm^2$. Efficiencies and short circuit current density increased as tape casting thickness decreased. Modified surface area of the photo electrode by needle stamp processing were studied. 200 times needle stamp processing on photo electrodes shows a highest 5.168% efficiency. Also the short circuit current density was a $10.261mA/cm^2$.

Solution processed organic photodetector utilizing an interdiffused polymer/fullerene bilayer

  • Shafian, Shafidah;Jang, Yoonhee;Kim, Kyungkon
    • Proceedings of the Korean Vacuum Society Conference
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    • pp.348-348
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    • 2016
  • Low dark current (off-current) and high photo current are both essential for a solution processed organic photodetector (OPD) to achieve high photo-responsivity. Currently, most OPDs utilize a bulk heterojunction (BHJ) photo-active layer that is prepared by the one-step deposition of a polymer:fullerene blend solution. However, the BHJ structure is the main cause of the high dark current in solution processed OPDs. It is revealed that the detectivity and spectral responsivity of the OPD can be improved by utilizing a photo-active layer consisting of an interdiffused polymer/fullerene bilayer (ID-BL). This ID-BL is prepared by the sequential solution deposition (SqD) of poly(3-hexylthiophene) (P3HT) and [6,6] phenyl C61 butyric acid methyl ester (PCBM) solutions. The ID-BL OPD is found to prevent undesirable electron injection from the hole collecting electrode to the ID-BL photo-active layer resulting in a reduced dark current in the ID-BL OPD. Based on dark current and external quantum efficiency (EQE) analysis, the detectivity of the ID-BL OPD is determined to be $7.60{\times}1011$ Jones at 620 nm. This value is 3.4 times higher than that of BHJ OPDs. Furthermore, compared to BHJ OPDs, the ID-BL OPD exhibited a more consistent spectral response in the range of 400 - 660 nm.

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Analytical Modeling for Dark and Photo Current Characteristics of Short Channel GaAs MESFETs (단채널 GaAs MESFET의 DC특성 및 광전류 특성의 해석적 모델에 대한 연구)

  • 김정문;서정하
    • Journal of the Institute of Electronics Engineers of Korea SD
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    • v.41 no.3
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    • pp.15-30
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    • 2004
  • In this paper, an analytical modeling for the dark and photo-current characteristics of a buried-gate short- channel GaAs MESFET is presented. The presented model shows that the increase of drain current under illumination is largely due to not the increase of photo-conductivity in the neutral region but the narrowing effect of the depletion layer width. The carrier density profile within the neutral region is derived from solving the carrier continuity equation one-dimensionally. In deriving the photo-generated current, we assume that the photo-current is compensated with the thermionic emission current at the gate-channel interface. Moreover, the two-dimensional Poisson's equation is solved by taking into account the drain-induced longitudinal field effect. In conclusion, the proposed model seems to provide a reasonable explanation for the dark and photo current characteristics in a unified manner.

In2S3 Co-Sensitized PbS Quantum Dot Solar Cells

  • Basit, Muhammad Abdul;Park, Tae Joo
    • Proceedings of the Korean Institute of Surface Engineering Conference
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    • pp.273-273
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    • 2014
  • Quantum-dot sensitized solar cells (QDSCs) are an emerging class of solar cells owing to their easy fabrication, low cost and material diversity. Despite of the fact that the maximum conversion efficiency of QDSCs is still far less than that of Dye-Sensitized Solar Cells (>12 %), their unique characteristics like Multiple Exciton Generation (MEG), energy band tune-ability and tendency to incorporate multiple co-sensitizers concurrently has made QDs a suitable alternative to expensive dyes for solar cell application. Lead Sulfide (PbS) Quantum dot sensitized solar cells are theoretically proficient enough to have a photo-current density ($J_{sc}$) of $36mA/cm^2$, but practically there are very few reports on photocurrent enhancement in PbS QDSCs. Recently, $Hg^{2+}$ incorporated PbS quantumdots and Cadmium Sulfide (CdS) co-sensitized PbS solarcells are reported to show an improvement in photo-current density ($J_{sc}$). In this study, we explored the efficacy of $In_2S_3$ as an interfacial layer deposited through SILAR process for PbS QDSCs. $In_2S_3$ was chosen as the interfacial layer in order to avoid the usage of hazardous CdS or Mercury (Hg). Herein, the deposition of $In_2S_3$ interfacial layer on $TiO_2$ prior to PbS QDs exhibited a direct enhancement in the photo-current (Isc). Improved photo-absorption as well as interfacial recombination barrier caused by $In_2S_3$ deposition increased the photo-current density ($J_{sc}$) from $13mA/cm^2$ to $15.5mA/cm^2$ for single cycle of $In_2S_3$ deposition. Increase in the number of cycles of $In_2S_3$ deposition was found to deteriorate the photocurrent, however it increased $V_{oc}$ of the device which reached to an optimum value of 2.25% Photo-conversion Efficiency (PCE) for 2 cycles of $In_2S_3$ deposition. Effect of Heat Treatment, Normalized Current Stability, Open Circuit Voltage Decay and Dark IV Characteristics were further measured to reveal the characteristics of device.

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Ellipso-Microscopic Observation of Titanium Surface under UV-Light Irradiation

  • Fushimi, K.;Kurauchi, K.;Nakanishi, T.;Hasegawa, Y.;Ueda, M.;Ohtsuka, T.
    • Corrosion Science and Technology
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    • v.15 no.6
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    • pp.265-270
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    • 2016
  • The ellipso-microscopic observation of a titanium surface undergoing anodization in $0.05mol\;dm^{-3}$ of $H_2SO_4$ was conducted. During irradiation by ultra-violet (UV) light with a wavelength of 325 nm, the titanium surface allowed for the flow of a photo-induced current and showed up as a bright, patch-like image on an ellipso-microscopic view. The brightness and patch-pattern in the image changed with flowing photo-induced current. The changes in the brightness and the image corresponded to the formation and/or degradation of titanium oxide due to the photo-electrochemical reaction of the oxide. An in situ monitoring using the ellipso-microscope revealed that the film change was dependent on the irradiation light power, by UV-light increases the anodic current and results in the initiation of pitting at lower potentials as compared with the non-irradiated condition.

a-Si:H Photodiode Using Alumina Thin Film Barrier

  • Hur Chang-Wu;Dimitrijev Sima
    • Journal of information and communication convergence engineering
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    • v.3 no.4
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    • pp.179-183
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    • 2005
  • A photodiode capable of obtaining a sufficient photo/ dark current ratio at both forward bias state and reverse bias state is proposed. The photodiode includes a glass substrate, an aluminum film formed as a lower electrode over the glass substrate, an alumina film formed as an insulator barrier over the aluminum film, a hydrogenated amorphous silicon film formed as a photo conduction layer over a portion of the alumina film, and a transparent conduction film formed as an upper electrode over the hydro-generated amorphous silicon film. A good quality alumina $(Al_2O_3)$ film is formed by oxidation of aluminum film using electrolyte solution of succinic acid. Alumina is used as a potential barrier between amorphous silicon and aluminum. It controls dark-current restriction. In case of photodiodes made by changing the formation condition of alumina, we can obtain a stable dark current $(\~10^{-12}A)$ in alumina thickness below $1000{\AA}$. At the reverse bias state of the negative voltage in ITO (Indium Tin Oxide), the photo current has substantially constant value of $5{\times}10^{-9}$ A at light scan of 100 1x. On the other hand, the photo/dark current ratios become higher at smaller thicknesses of the alumina film. Therefore, the alumina film is used as a thin insulator barrier, which is distinct from the conventional concept of forming the insulator barrier layer near the transparent conduction film. Also, the structure with the insulator thin barrier layer formed near the lower electrode, opposed to the ITO film, solves the interface problem of the ITO film because it provides an improved photo current/dark current ratio.

Enhanced Photo Current in n-ZnO/p-Si Diode Via Embedded Ag Nanoparticles for the Solar Cell Application

  • Ko, Young-Uk;Yun, Ho-Jin;Jeong, Kwang-Seok;Kim, Yu-Mi;Yang, Seung-Dong;Kim, Seong-Hyeon;Kim, Jin-Sup;An, Jin-Un;Eom, Ki-Yun;Lee, Hi-Deok;Lee, Ga-Won
    • JSTS:Journal of Semiconductor Technology and Science
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    • v.15 no.1
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    • pp.35-40
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    • 2015
  • In this study, an n-ZnO/p-Si heterojunction diode with embedded Ag nanoparticles was fabricated to investigate the possible improvement of light trapping via the surface plasmon resonance effect for solar cell applications. The Ag nanoparticles were fabricated by the physical sputtering method. The acquired current-voltage curves and optical absorption spectra demonstrated that the application of Ag nanoparticles in the n-ZnO/p-Si interface increased the photo current, particularly in specific wavelength regions. The results indicate that the enhancement of the photo current was caused by the surface plasmon resonance effect generated by the Ag nanoparticles. In addition, minority carrier lifetime measurements showed that the recombination losses caused by the Ag nanoparticles were negligible. These results suggest that the embedding of Ag nanoparticles is a powerful method to improve the performance of n-ZnO/p-Si heterojunction solar cells.

Properties of Photo-regulation of Liquid Crystal Alignment and Generation of Maxwell-displacement-current for Application with a Medical Engineering Device (의료용 초박막 액정의 광배향 제어와 광변위 전류 특성)

  • Lee, Ho-Shik;Ahn, Joon-Ho;Kim, Woo-Yeon;Iwamoto, M.;Lee, Won-Jae
    • Journal of the Korean Institute of Electrical and Electronic Material Engineers
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    • v.19 no.12
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    • pp.1160-1166
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    • 2006
  • Maxwell-displacement-current (MDC) measuring technique has been applied for the investigation of monolayers of poly(vinyl alcohol)s bearing azobenzene side-chains (6Az5PVA) mixed with p-pentyl-p'-cyano-biphenyls (5CBs) on a water surface. For mixed monolayers containing trans-form 6Az5PVA and LCs, displacement current due to photo isomerization was not generated with alternative photo-irradiation with UV and svisible light. In contrast, for mixed monolaters containing cis-form 6Az5PVA and LCs, displacement current was generated. Finally, it was found that the alignment layers deposited in cis-form could photoregualte the orientation of LCs.

Characteristics of $SnO_2$/a-Se/AI sample ($SnO_2$/a-Se/AI 소자의 특성)

  • 박계춘;정운조;유용택
    • Electrical & Electronic Materials
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    • v.7 no.1
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    • pp.7-14
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    • 1994
  • Structural and optical characteristics in $SnO_2$/a-Se/Al sample by aging variation and applying constant voltage had been investigated. a-Se was varied with monoclinic structure and its surface was greatly exchanged. Its capacitance was first decreased and then increased and its photo-current, photo-voltage and photo-capacitance were increased gradually with day and applying voltage. From the results, crystallization of a-Se and dopant trap level formation had been identified. Also, it was acknowledged $SnO_2$/a-Se/Al sample is useful in photovoltaic and solid thin film cell.

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