This application makes reference to, incorporates the same herein, and claims all benefits accruing under 35 U.S.C. §119 from an application for PHOTOVOLTAIC DEVICE, LAMP AND DISPLAY PANEL ADOPTING THE DEVICE earlier filled in the Korean Intellectual Property Office on Dec. 23, 2004 and there duly assigned Serial No. 10-2004-0111108.
1. Field of the Invention
The present invention relates to a photovoltaic device and a lamp and a display using the photovoltaic device, and more particularly, to a photoelectric field emitter and a lamp adopting the photoelectric field emitter which make use of primary electrons based on a photoelectric effect and the emission of secondary electrons using the primary electrons.
2. Description of the Related Art
A conventional photocathode discussed in U.S. Pat. No. 4,616,248 employs an alkali halide material, such as CsI, which emits electrons when irradiated by ultraviolet (UV) light, to generate a feeble current. This photocathode requires not only an amplifier for amplifying the feeble current using a micro-channel-plate photomultiplier tube (MCP-PMT) or an electrical circuit, but also other additional devices.
Owing to the increased demand for photocathodes, it is necessary to improve their luminous efficiency and current density and further expand their range of application.
The present invention provides a photovoltaic device with a high luminous efficiency and high current density and a lamp and a display device using the photovoltaic device.
According to an aspect of the present invention, there is provided a photovoltaic device including a substrate; a conductive electric field enhanced layer including a plurality of partial electric field crowding end portions disposed on the substrate; an electron amplification layer disposed on the electric field enhanced layer and formed of a material that emits secondary electrons; and a photoelectric material layer disposed on the electron amplification layer.
In the photovoltaic device, the electric field enhanced layer can be a carbon nano-tube (CNT) layer having a bundle of CNTs which are vertically grown on the substrate or obtained by coating a paste on the substrate and sintering the same.
In order to supply a bias voltage to the electric field enhanced layer (i.e., the CNT layer), a bias electrode layer can be disposed under the electric field enhanced layer.
According to another aspect of the present invention, there is provided a photovoltaic device including a first electrode and a second electrode spaced apart from each other; a conductive electric field enhanced layer including a plurality of partial electric field crowding end portions disposed on a surface of the first electrode opposite the second electrode; an electron amplification layer disposed on the electric field enhanced layer and formed of material that emits secondary electrons; and a photoelectric material layer disposed on the electron amplification layer.
According to yet another aspect of the present invention, there is provided a photoelectric lamp including a first electrode and a second electrode spaced a predetermined distance apart from each other; a conductive electric field enhanced layer including a plurality of partial electric field crowding end portions disposed on a surface of the first electrode opposite the second electrode; an electron amplification layer disposed on the electric field enhanced layer and formed of a material that emits secondary electrons; a photoelectric material layer disposed on the electron amplification layer; and a phosphor layer disposed on the second electrode.
According to further another aspect of the present invention, there is provided a display device including a substrate; a cathode electrode disposed on the substrate; a gate dielectric layer that is disposed on the cathode electrode and has a well that exposes a portion of the cathode electrode; a photoelectric field emission layer that is disposed on the portion of the cathode electrode that is exposed by the well and includes: a conductive electric field enhanced layer including a plurality of partial electric field crowding end portions; and an electron amplification layer disposed on the electric field enhanced layer and formed of a material that emits secondary electrons; and a gate electrode that is disposed on the gate dielectric layer and has a gate hole corresponding to the well.
A more complete appreciation of the present invention, and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:
A photovoltaic device and a lamp and display device using the photovoltaic device according to the present invention will now be described more fully hereinafter with reference to the accompanying drawings, in which exemplary embodiments of the present invention are shown. In the exemplary embodiments, an electric field enhanced layer refers to a conductive stacked layer that is composed of any material capable of electric field crowding and electric field emission under predetermined conditions.
Referring to
The photoelectric field emitter can be applied as an electronic source (i.e., a cathode) to a variety of electronic devices and utilized in various fields, such as a photosensor for detecting light.
A substrate for supporting the photoelectric field emitter can be a silicon substrate, and the electric field enhanced layer can be formed of single-walled nano tubes (SWNTs) or multi-walled nano tubes (MWNTs). Also, the electron amplification layer for emitting the secondary electrons can be formed of at least one component selected from the group consisting of MgF2, CaF2, LiF, MgO, SiO2, Al2O3, ZnO, CaO, SrO, and La2O3. Often, the use of MgO is advantageous. The photoelectric material layer can be formed of a conventionally used material which absorbs light energy and emits electrons, for example, CsI. In addition, any material that emits electrons by UV or visible irradiation can be used instead of CsI. For example, the photoelectric material layer can be formed of an oxide material or compound material containing at least one alkali metal selected from the group consisting of Ba, Cs, K, Rb, Na, Mg, and Ca or a metal selected from the group consisting of Pt, W, Cu, Au, Ag, Si, and Ge. Specifically, the photoelectric material layer can be formed of at least one component selected from the group consisting of BaO, Ag—O—Cs, Bi—Ag—O—Cs, K—Cs—Sb, Na—K—Sb, Cs—Na—K—Sb, Li3Sb, Cs2Te, Cs3Sb, LiF, Na2KSb:Cs, GaN, InP, HgTe, CdS, CdSe, PbS, PbTe, InAs, KBr, CsBr, and CsI.
Referring to
An electric field enhanced layer 12 including a plurality of partial electric field crowding end portions, which are physically pointed portions, is formed on the first electrode 11. The partial electric field crowding end portions can be nano-tips, nano-particles, or CNTs, which are commonly used in electric field emission devices.
In embodiments of the present invention, the CNTs are used not as a main electron source as in a conventional Field Emission Display (FED), but as a source for producing primary electrons. That is, an electron amplification layer 13 (e.g., a MgO layer) which can emit secondary electrons is formed on the electric field enhanced layer 12. Thus, the primary electrons are emitted from the electric field enhanced layer 12 to the electron amplification layer 13 so that electrons are amplified to secure a larger number of electrons. Furthermore, a photoelectric material layer 14 (e.g., a CsI layer) is formed on the electron amplification layer 13 to emit electrons in response to excitation light, such as UV or DUV light.
The second electrode 21 is formed opposite the first electrode 11 on the inner surface of the second substrate 20, and a predetermined voltage is supplied between the first and second electrodes 11 and 21. The UV light, which stimulates the photoelectric material layer 14 to emit the electrons, proceeds in a direction parallel to the substrates 10 and 20 or through the second substrate 20.
The photovoltaic device with the above-described structure can be employed as a photosensor. That is, once excitation light, such as UV light, is incident between the first and second substrates 10 and 20 during the application of a predetermined bias voltage between the first and second electrodes 11 and 21, a current flows between the first and second electrodes 11 and 21. The current amount varies according to the intensity of the incident light. When no excitation light is incident, the bias voltage is maintained at such an electrical potential that no current flows.
Referring to
An electron amplification layer formed of MgO had a fixed thickness of 200 nm, and the photoelectric material layer formed of CsI had thicknesses of 10, 30, 40, 60, and 80 nm in respective embodiments. As can be seen from
Referring to
A first electrode 11 is formed as a cathode electrode on an inner surface of the first substrate 10, and a second electrode 21 is formed as an anode electrode on an inner surface of the second substrate 20.
A phosphor layer is formed on an inner surface of the second electrode 21. The phosphor layer is excited by accelerated electrons and emits visible light. The acceleration of the electrons occurs due to an electrical potential difference between the first and second electrodes 11 and 21. To obtain the electrical potential difference, the first and second electrodes 11 and 21 are connected to a power supply source 30.
A cathode apparatus, which produces a large number of electrons, is comprised of a primary electron source (or an electric field enhanced layer) 15, an electron amplification layer 13, and a photoelectric material layer 14. The electric field enhanced layer 15 is disposed on the first electrode 11 and formed of CNTs, and the electron amplification layer 13 is formed of MgO and amplifies electrons produced by the electric field enhanced layer 12. The photoelectric material layer 14 is formed of CsI and emits electrons when irradiated with UV light. Other materials forming the elements included in the cathode apparatus can be selected by those skilled in the art without departing from the scope of the present invention.
On comparing
Because a lamp requires a large current, unlike a photosensor as described above, a voltage supplied between the first and second electrodes 11 and 21 can be high such that an electric field is generated even without excitation light.
The above-described flat panel lamp can be applied in various fields, for example, backlights that must provide visible light with a high luminance. Alternatively, the flat panel lamp can be further structurally modified and applied to typical display devices.
As described above, a flat panel display device can be obtained by applying a visible ray emission structure to the flat panel lamp of the previous embodiment.
As shown in
The display device according to an embodiment of the present invention can be obtained by organically combining the above-described lamp structure according to the previous embodiment with an Organic Light Emitting Display (OLED).
In an OLED, the row electrodes correspond to gate electrodes, and the column electrodes correspond to cathode electrodes.
Light (e.g., UV light) for stimulating the CsI layer can be incident on the CsI layer in a direction parallel to the substrate 40 or through a rear surface of the substrate 40.
An additional substrate is prepared opposite a front surface of the substrate 40. The additional substrate is typically referred to as a front plate. An anode electrode corresponding to the cathode electrode and a phosphor layer are formed on the additional substrate. If the phosphor layer must be excited by electronic beams instead of UV (or DUV) light, it can be formed of a known material appropriately selected by a person of ordinary skill in the art.
As described above, the present invention provides a photoelectric field emitter. The photoelectric field emitter includes an electric field enhanced layer, which includes partial electric field crowding end portions (i.e., physically pointed portions), an electron amplification layer, which amplifies primary electrons produced by the electric field enhanced layer, and a photoelectric material layer, which is excited by light and emits electrons. The photoelectric field emitter can be applied to various fields, such as photosensors, lamps, and display devices.
A lamp and a display device using the photoelectric field emitter provides visible light with a high luminance even at a low voltage and a low current through the amplification of electrons using the electron amplification layer.
The photoelectric field emitter of the present invention makes use of light of various wavelengths and can be utilized in photosensors, flat panel light sources, solar batteries, and display devices.
While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various modifications in form and detail can be made therein without departing from the spirit and scope of the present invention as defined by the following claims.
Number | Date | Country | Kind |
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10-2004-0111108 | Dec 2004 | KR | national |