Studies on primary photocurrent of a-Si:H using xerographic and vidicon techniques
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The primary photocurrent of a‐Si:H prepared by glow discharge of SiH4 was investigated with VIDICON and ELECTROPHOTOGRAPHIC techniques. The photoresponse current depends greatly upon the device structures used and an excellent photoconductivity gain of unity is attainable if the leakage current in the dark is excluded. All results in this study can be interpreted in terms of field‐independent efficiency for carrier‐generation in a‐Si:H.Keywords:
Photocurrent
Photoconductivity
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In this paper we present, for a CMOS n-diffusion photodiode, the effects of various doping concentrations on the behaviour of two of the main parameters that characterize the performance of these devices: the photocurrent (for low and for high levels of the illumination) and the dark current. We performed simulations aided by T-CAD tools for each type of layer of the CMOS photodiode structure (substrate, p-epitaxial layer, n-diffusion layer) and evaluated the behaviour of the photocurrent and dark current in various levels of the doping concentrations of these layers. These results may be helpful in the process of fabricating these devices, where controlled amounts of impurities may be added to some layers (or their level might be reduced in some other layers), in order to maximize the photocurrent and to minimize the dark current in these structures.
Photocurrent
Photodiode
Photoconductivity
Diffusion current
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Ultra-long AlN nanowire arrays are prepared by chemical vapor deposition, and the photoconductive performances of individual nanowires are investigated in our self-built measurement system. Individual ultra-long AlN nanowire (UAN) exhibits a clear photoconductive effect under different excited lights. We attribute the positive photocurrent response of individual UAN to the dominant molecular sensitization effect. It is found that they have a much faster response speed (a rise and decay time of about 1 ms), higher photocurrent response (2.7×106), and more reproductive working performance (the photocurrent fluctuation is lower than 2%) in the air environment. Their better photoconductive performances are comparable to many nanostructures, which are suggested to be a candidate for building promising photosensitive nanodevices in the future.
Photoconductivity
Photocurrent
Nanochemistry
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Measurements of quantum efficiency and photoconductivity on dye-sensitized ZnO powder-organic-resin binder layers as used in electrophotography show that the carrier range for dye-sensitized photocurrents is 10 to 100 times lower than that for the intrinsic ZnO photocurrent at 3800 Å. The dye-sensitized photocurrent depends on the square root of light intensity while the photocurrent at 3800 Å is linear with intensity. These observations are interpreted in terms of a bimolecular recombination process for the dye-sensitized photocurrent in which a photoexcited dye molecule injects an electron into the ZnO conduction band and then recaptures ZnO conduction electrons to return to the ground state.
Photocurrent
Photoconductivity
Quantum yield
Quantum Efficiency
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The primary photocurrent of a‐Si:H prepared by glow discharge of SiH4 was investigated with VIDICON and ELECTROPHOTOGRAPHIC techniques. The photoresponse current depends greatly upon the device structures used and an excellent photoconductivity gain of unity is attainable if the leakage current in the dark is excluded. All results in this study can be interpreted in terms of field‐independent efficiency for carrier‐generation in a‐Si:H.
Photocurrent
Photoconductivity
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Currently, colloidal quantum dots (CQDs)-based photodetectors are widely investigated due to their low cost and easy integration with optoelectronic devices. The requirements for a high-performance photodetector are a low dark current and a high photocurrent. Normally, photodetectors with a low dark current also possess a low photocurrent, or photodetectors with reduced dark current possess a reduced photocurrent, resulting in low detectivity. In this paper, a solution to suppress dark current and maintain a high photocurrent, i.e., use of poly(methyl methacrylate) doped with Au nanoparticles (NPs) (i.e., PMMA:Au) as an interlayer for enhanced-performance tandem photodetectors, is presented. Our experimental data showed that the dark current through the tandem photodetector ITO/PEDOT:PSS/PbS:CsSnBr3/ZnO/PMMA:Au/CuSeN/PbS:CsSnBr3/ZnO/Ag is suppressed significantly; meanwhile, a high photocurrent is maintained after a PMMA:Au interlayer has been inserted between two subdetectors. The inserted PMMA:Au interlayer acts as storage nodes for electrons, reducing the dark current through the device; meanwhile, the photocurrent can be enhanced under illumination. As a result, the specific detectivity of the tandem photodetector with 35 nm PMMA:Au interlayer was enhanced significantly from 5.01 × 1012 to 2.7 × 1015 Jones under 300 μW/cm2 532 nm illumination at a low voltage of -1 V as compared to the device without a PMMA:Au interlayer. Further, the physical mechanism of enhanced performance is discussed in detail.
Photocurrent
Tandem
Quantum Efficiency
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We have developed a two-dimensional theoretical model. This model allowed us to characterize the MSM photodetector based ZnO. It also allowed us to simulate the dark current and photocurrent of the device with different dimensions of the metal contact of structure. The simulation results were agreed with those of the experiment. We have identified the influence of geometry parameters of the metal contact on the dark current and also on the photocurrent. Calculating the ratio (photocurrent / dark current), allowed us to find the best values of finger width w and finger spacing s of the metal structure leading to a low dark current and at the same time a better absorption of the incident light. The best performance of MSM PD are obtained for the following values s = 14 μm, w = 12 microns. These values have enabled us to obtain a dark current of 25nA and a photocurrent equal to 0.78 μA at a 3V bias.
Photocurrent
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Photoconductivity in nanocrystal films has been previously characterized, but memory effects have received little attention despite their importance for device applications. We show that the magnitude and temperature dependence of the photocurrent in CdSe/ZnS core-shell nanocrystal arrays depends on the illumination and electric field history. Changes in photoconductivity occur on a few-hour timescale, and subband gap illumination of nanocrystals prior to measurements modifies the photocurrent more than band gap illumination. The observed effects can be explained by charge traps within the band gap that are filled or emptied, which may alter nonradiative recombination processes and affect photocurrent.
Photoconductivity
Photocurrent
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Photoconductivity
Photocurrent
Photosensitivity
Light intensity
Intensity
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In the present paper, photoconductivity (PC) of Zinc-oxide (ZnO) nanostructures synthesized by sol-gel method has been investigated. Structural study has been performed by X-ray diffraction (XRD) patterns. The XRD result confirms the formation of hexagonal phase. In the photoconductivity analysis, growth and decay of photocurrent of ZnO nanostructures have been investigated. The photo-response of prepared sample has been measured underUV illumination using thick film of powder without any binder. The growth and decay of photocurrent show fastrise and decay of photocurrent indicating suitability for UV photodetectors applications
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Photoconductivity
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Photocurrent
Photoelectric effect
SIGNAL (programming language)
Response time
Ultraviolet
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