US3502885A - Non-coplanar electrode photoconductor structure and electroluminescent-photoconductor array - Google Patents

Non-coplanar electrode photoconductor structure and electroluminescent-photoconductor array Download PDF

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US3502885A
US3502885A US662135A US3502885DA US3502885A US 3502885 A US3502885 A US 3502885A US 662135 A US662135 A US 662135A US 3502885D A US3502885D A US 3502885DA US 3502885 A US3502885 A US 3502885A
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photoconductor
electroluminescent
electrode
electrodes
light
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US662135A
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Richard D Stewart
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General Electric Co
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General Electric Co
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/12—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof structurally associated with, e.g. formed in or on a common substrate with, one or more electric light sources, e.g. electroluminescent light sources, and electrically or optically coupled thereto

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  • Photoconductor structures have in the past been fabricated principally with either a coplanar or parallel plane electrode configuration.
  • coplanar structure interdigital electrodes are normally employed, either overlaying or underlaying the photoconductive material.
  • parallel plane electrode structure the photoconductive material is sandwiched between an electrode pair.
  • Neither of these configurations has been found to be completely satisfactory when construction of the photoconductor is integral with an electroluminescent array to control the light output thereof in an optical amplification or a conversion device.
  • the limitations become more pronounced for high resolution requirements, e.g., above ten lines per inch.
  • the photoconductors are employed to apply a source voltage across the electroluminescent cells as a function of a light input to thereby control the light emission.
  • the photoconductor structure must have photoconductive characteristics which provide sufficiently large differences in conductivity between light and dark conditions.
  • the structure must be capable of supporting relatively large vo tages for dark conditions, so that for these conditions sufliciently low voltage levels Will exist across the electroluminescent cells.
  • the photoconductor structure exhibit adequate sensitivity to applied low light levels.
  • the photoconductive structure lend itself to an easy fabrication when integrally combined with an electroluminescent array.
  • the parallel plane electrodes structure although exhibit'ing a relatively good optical efficiency, exhibits a capacitance between the parallel electrodes that is large relative to the capacitance of standard electroluminescent cells, which require A-C voltage sources. Hence, the admittance of the photoconductor in the dark state remains relatively high, as does the minimum voltage across the electroluminescent cells. Therefore, the electroluminescent cells are not readily switched between light and dark states. This capacitance cannot be adequately reduced by further separation of the electrodes because the photoconductor thickness then precludes effective light penetration.
  • Itv is accordingly an object of the invention to provide a novel photoconductor structure exhibiting a wide impedance variation between conditionts of total exposure and nonexposure by means of a readily achieved fabrication.
  • the photoconductor structure which utilizes a non-coplanar, concentric arrangement of electrodes.
  • the photoconductor structure includes a first apertured electrode and a further electrode of dimensions smaller than the aperture of said apertured electrode concentrically arranged with the apertured electrode and spaced therefrom by a photoconductive material sandwiched between the electrodes.
  • the entire structure is supported by a transparent substrate on which the apertured electrode has been deposited.
  • the electrical conduction path of the photoconductor extends from approximately the edge of the aperture of said apertured in contact with the photoconductor:
  • the photoconductor structure When embodied in an electroluminescent-photoconductor image converter or amplifier device, the photoconductor structure is fabricated in array form and is overlayed by an electroluminescent layer, the external surface of which is coated with a transparent electrode.
  • FIGURE 1 is a plan view, partially broken away, of a photoconductor structure in accordance with the invention
  • FIGURE 2 is a cross sectional view taken through the plane 22 in FIGURE 1;
  • FIGURE 3 is a plan view, partially broken away, of an electroluminescent-photoconductor image converter or amplifying device employing a photoconductor structure similar to that shown in FIGURES 1 and 2;
  • FIGURE 4 is a cross sectional view taken through the plane 44 in FIGURE 3;
  • FIGURE 5 is an electrical equivalent circuit for the structure of FIGURES 3 and 4;
  • FIGURE 6 is a graph of the light output versus the photoconductor resistance of the electroluminescentphotoconductor device of FIGURES 3 and 4.
  • FIGURE 1 there is illustrated a partially broken away plan view of a photoconductor structure 1 in accordance with the invention, which shows the various layers of the structure.
  • the structure 1 includes a common electrode 2 having apertures 3 provided therein and individual electrodes 4 concentrically arranged with respect to the apertures 3, the electrodes 4 having smaller dimensions than said apertures.
  • a photoconductor material 5 extends between the common electrode 2 and the individual electrodes 4, filling the apertures 3.
  • An insulating layer 6 having holes formed therein electrically insulates the photoconductive material from external connection at areas between the individual electrodes, as well as limits the effective area of the electrodes in contact with the photoconductor 5.
  • FIG. 2 As more clearly shown in the cross sectional view of FIGURE 2 taken along the plane 2-2 in FIGURE 1, the entire structure is mounted upon a glass substrate 7. For purposes of clarity, the view of FIGURE 2 is not to scale.
  • the common electrode 2 and the individual electrodes 4 are in different planes, effectively offset from each other so as to reduce the capacitance between them.
  • the electrodes 4 are typically in the form of indium pellets.
  • a reflective metal film 8, such as gold or aluminum, deposited on the surface of the photoconductor 5 insures good electrical contact between the photoconductive material and the individual conductor pellets 4.
  • Conductor leads 9 and 10 are connected to the common electrode 2 and individual electrodes 4, respectively.
  • the photoconductor structure 1 is fabricated using processes that are standard in the art.
  • the common electrode 2 is a platinum material that is applied to the glass substrate 7, having a thickness of about 10 mils, by means of a reverse photoresist method wherein a photoresist material such as KPR is deposited upon the surface of the glass substrate in those areas where the apertures 3 are to be formed.
  • the platinum is sputtered over the entire surface of the glass to a thickness of approximately 2000-5000 angstroms.
  • the photoresist material dissolves carrying away with its the overlaying platinum. The remaining platinum material is undisturbed and the common electrode layer 2 is thereby formed with the apertures 3, these being approximately 40 mils in diameter in one operable embodiment of the invention.
  • a photoconductive material such as CdSe or CdS is mixed in a sintered powdered form in an alcohol slurry, sprayed over the common electrode layer to a thickness of about 1-2 mils and fired so as to achieve the desired photoconductive properties and to adhere at the undersurface.
  • a metallic film of gold or aluminum is then evaporated onto the surface of the photoconductor through a mask, not shown, so as to form the coatings 8 within the area of the apertures 3.
  • the conductive coatings each have a diameter of about 20 mils in the operable embodiment being considered, with the minimum conduction path therefore slightly more than 10 mils.
  • the relative dimensions between the individual electrodes and the apertures may be somewhat different from that indicated.
  • the photoconductor resistance can be decreased, the limit being the dimension at which voltage breakdown occurs through the photoconductor material. Conversely, the photoconductor resistance is increased by increasing the electrode spacing.
  • the insulating member 6 which is a plastic layer such as mylar having holes therein of the same dimension as the conductive coatings 8, is next laid over the structure thus far formed.
  • the member 6 has a thickness of approximately 7-8 mils in the operable embodiment being considered.
  • the holes in the member 6 are then filled with individual indium pellets, a material of relatively low melting point permitting it to flow at a temperature that will not adversely affect electroluminescent material.
  • the entire structure is then laminated together under the application of heat to about C. and pressure to about 20 p.s.i.
  • FIGURES 3 and 4 there is illustrated an electroluminescent-photoconductor device 20 providing image conversion or amplification, which structure employs the basic photoconductor structure 1 of FIGURES l and 2.
  • FIGURE 3 is a partially broken away plan view
  • FIGURE 4 is a cross sectional view of FIGURE 3 taken along the plane 44. Elements that are repeated in FIGURES 3 and 4 are identified with the same reference characters as previously, but with an added prime notation.
  • the device 20 is seen to be different from that hereinbefore considered only in the addition of an electroluminescent layer 21 and a slightly modified configuration of the individual electrodes 4'.
  • the individual electrodes 4' and the insulating layer 6 are opaque to light energy emitted by the electroluminescent cell.
  • the individual electrodes provide discrete connections of the photoconductor elements to the electroluminescent film so as to control the voltage across elemental portions of the electroluminescent layer and thus the light emission therefrom.
  • the electroluminescent layer 21 includes an electroluminescent malterial 22 and a transparent common electrode 23 deposited thereon.
  • a standard electroluminescent material that may be employed includes a zinc sulphide phosphor embedded in a plastic binder, such as manufactured by General Electric Company.
  • a pair of conducting leads 24 and 25 are connected to the transparent electrode 23 and the common electrode 2, respectively.
  • An A-C source voltage 26 is provided for energizing the electroluminescent photoconductor structure.
  • the elemental resistivity of the individual photoconductor elements will vary as a function of the light energy intensity so as to cause an according variation of voltage across corresponding portions of the electroluminescent layer 21.
  • Optical feedback is prevented from occurring between the electroluminescent and the photoconductor elements by means of the opaque insulating layer 6 and the electrode pellets 4.
  • FIGURE 5 An electrical equivalent circuit for the electroluminescent-photoconductor device of FIGUR'ES 3 and 4 is shown in FIGURE 5.
  • the structure includes a plurality of electroluminescent-photoconductor shunt paths each including a photoconductor element 30 in series with an electroluminescent element 31.
  • the shunt paths are connected between the photoconductor common electrode and the electroluminescent common electrode, and across the A-C voltage source 26.
  • each photoconductor it is necessary that the light resistance of each photoconductor be appreciably smaller than the impedance of the associated electroluminescent element so that for an exposed photoconductor the source voltage is primarily across the electroluminescent element, causing it to brightly emit light.
  • the dark resistance of the photoconductor should be considerably greater than the impedance of the electroluminescent element so that very little voltage is across it and no light emission will occur.
  • the capactive reactance of the photoconductor be large in order that the photoconductor support sufficient voltage in the dark condition for extinguishing the electroluminescent element, and so that the impedance of the photoconductor is widely variable as a function of its light sensitive resistance.
  • a panel of 400 pairs of elements was constructed, 20 on a side.
  • the capacitance of each photoconductor element was found to be 1.25 l0" farads. As compared to the capacitance of the corresponding electroluminescent element, this yielded a ratio between capacitances C /C of 800.
  • a light output in percent vs. photoconductor resistance characteristic was obtained, as shown by the curve in FIGURE 6.
  • the photoconductor resistance is seen to be effective in controlling light output of the electroluminescent layer from output down to essentially zero emission.
  • the photoconductor capacitance for example on the order of that of the electroluminescent element, the light output cannot be reduced to less than about 30% emission no matter how high the photoconductor resistance becomes, due to the limiting capacitive reactance of the photoconductor.
  • a photoconductor structure comprising:
  • a photoconductor structure as in claim 1 that is in array form wherein said apertured electrode is a continuous layer of conductive material in which a plurality of apertures have been formed, said layer deposited on a transparent dielectric substrate, there being a plurality of further electrodes overlaying the photoconductive material, one for each aperture.
  • a photoconductor structure as in claim 2 which includes a continuous layer of insulating material in which a plurality of holes have been formed overlaying said photoconductive material, said further electrodes being located within said holes.
  • An electroluminescent-photoconductor device comprising:
  • An electroluminescent-photoconductor device as in claim 5 that is in array form wherein said apertured electrode is a continuous layer of conductive material in which a plurality of apertures have been formed, said layer deposited on a transparent dielectric substrate, there being a plurality of further electrodes overlaying said photoconductive material, one for each aperture.
  • An electroluminescent-photoconductor device as in claim 6 which includes a continuous layer of insulating material in which a plurality of holes have been formed overlaying said photoconductive material, said further electrodes being located within said holes.
  • An electroluminescent-photoconductor device as in claim 7 which includes a metallic film deposited on the surface of the photoconductive material and a metallic pellet bonded to said film.

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  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Computer Hardware Design (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Power Engineering (AREA)
  • Electroluminescent Light Sources (AREA)
US662135A 1967-08-21 1967-08-21 Non-coplanar electrode photoconductor structure and electroluminescent-photoconductor array Expired - Lifetime US3502885A (en)

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US66213567A 1967-08-21 1967-08-21

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JP (1) JPS4827651Y1 (fr)
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Cited By (9)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3638006A (en) * 1969-12-11 1972-01-25 Goodyear Aerospace Corp Solid-state correlator
US4015166A (en) * 1972-09-06 1977-03-29 Matsushita Electric Industrial Co., Ltd. X-Y matrix type electroluminescent display panel
US4307372A (en) * 1976-05-28 1981-12-22 Hitachi, Ltd. Photosensor
US4431913A (en) * 1980-12-04 1984-02-14 Fuji Xerox Co., Ltd. One-dimensional scanner
US4814668A (en) * 1982-05-19 1989-03-21 Matsushita Electric Industrial Co., Ltd. Electroluminescent display device
US5473340A (en) * 1990-09-27 1995-12-05 The United States Of America As Represented By The Secretary Of The Navy Apparatus for displaying a multi-color pattern
US20040233138A1 (en) * 2001-07-27 2004-11-25 Gunther Haas Image display panel consisting of a matrix of memory-effect electroluminescent cells
US20050156512A1 (en) * 2003-12-30 2005-07-21 Vadim Savvateev Electroluminescent devices with at least one electrode having apertures and methods of using such devices
CN100444423C (zh) * 2003-12-26 2008-12-17 上海广电电子股份有限公司 一种有机发光显示器件

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2923828A (en) * 1957-11-01 1960-02-02 Rca Corp Self-supported electrode structure and method of making same
US2975387A (en) * 1955-10-28 1961-03-14 Standard Register Co Grey metallic selenium photocells
US3317732A (en) * 1962-04-03 1967-05-02 Jenaer Glaswerk Schott & Gen Photosensitive device using glass of arsenic, sulfur and halogen; method of using the device; and method of making the glass
US3405276A (en) * 1965-01-26 1968-10-08 Navy Usa Image intensifier comprising perforated glass substrate and method of making same

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2975387A (en) * 1955-10-28 1961-03-14 Standard Register Co Grey metallic selenium photocells
US2923828A (en) * 1957-11-01 1960-02-02 Rca Corp Self-supported electrode structure and method of making same
US3317732A (en) * 1962-04-03 1967-05-02 Jenaer Glaswerk Schott & Gen Photosensitive device using glass of arsenic, sulfur and halogen; method of using the device; and method of making the glass
US3405276A (en) * 1965-01-26 1968-10-08 Navy Usa Image intensifier comprising perforated glass substrate and method of making same

Cited By (11)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3638006A (en) * 1969-12-11 1972-01-25 Goodyear Aerospace Corp Solid-state correlator
US4015166A (en) * 1972-09-06 1977-03-29 Matsushita Electric Industrial Co., Ltd. X-Y matrix type electroluminescent display panel
US4307372A (en) * 1976-05-28 1981-12-22 Hitachi, Ltd. Photosensor
US4431913A (en) * 1980-12-04 1984-02-14 Fuji Xerox Co., Ltd. One-dimensional scanner
US4814668A (en) * 1982-05-19 1989-03-21 Matsushita Electric Industrial Co., Ltd. Electroluminescent display device
US5473340A (en) * 1990-09-27 1995-12-05 The United States Of America As Represented By The Secretary Of The Navy Apparatus for displaying a multi-color pattern
US20040233138A1 (en) * 2001-07-27 2004-11-25 Gunther Haas Image display panel consisting of a matrix of memory-effect electroluminescent cells
CN100394629C (zh) * 2001-07-27 2008-06-11 汤姆森许可贸易公司 由记忆效应电致发光单元矩阵构成的图像显示面板
US7397181B2 (en) * 2001-07-27 2008-07-08 Thomson Licensing Image display panel consisting of a matrix of memory-effect electroluminescent cells
CN100444423C (zh) * 2003-12-26 2008-12-17 上海广电电子股份有限公司 一种有机发光显示器件
US20050156512A1 (en) * 2003-12-30 2005-07-21 Vadim Savvateev Electroluminescent devices with at least one electrode having apertures and methods of using such devices

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CA849741A (en) 1970-08-18
JPS4827651Y1 (fr) 1973-08-15
FR1578445A (fr) 1969-08-14

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