Batteries: thermoelectric and photoelectric – Photoelectric – Cells
Reexamination Certificate
1999-11-09
2001-05-29
Chapman, Mark (Department: 1753)
Batteries: thermoelectric and photoelectric
Photoelectric
Cells
C438S597000, C438S669000
Reexamination Certificate
active
06239356
ABSTRACT:
BACKGROUND
Field of Invention
This invention relates to the generation of electricity using photoemission and photoemission-thermionic hybrid generators.
Background—Photoelectric Conversion
In my previous application, entitled “Method and Apparatus for Photoelectric Generation of Electricity”, filed May 12th 1997, application Ser. No. 08/854,302, and incorporated herein by reference in its entirety, I disclose a Photoelectric Generator having close spaced electrodes separated by a vacuum. Photons impinging on the emitter cause electrons to be emitted as a consequence of the photoelectric effect. These electrons move to the collector as a result of excess energy from the photon: part of the photon energy is used escaping from the electrode and the remainder is conserved as kinetic energy moving the electron. This means that the lower the work function of the emitter, the lower the energy required by the photons to cause electron emission. A greater proportion of photons will therefore cause photo-emission and the electron current will be higher. The collector work function governs how much of this energy is dissipated as heat: up to a point, the lower the collector work function, the more efficient the device. However there is a minimum value for the collector work function: thermionic emission from the collector will become a problem at elevated temperatures if the collector work function is too low.
Collected electrons return via an external circuit to the cathode, thereby powering a load. One or both of the electrodes are formed as a thin film on a transparent material, which permits light to enter the device. A solar concentrator is not required, and the device operates efficiently at ambient temperature.
My previous invention further discloses a Photoelectric Generator which is constructed using micro-machining techniques. This allows the economic mass-production of Photoelectric Generators.
Background—Optical Discs
In a typical process for producing optical discs, molten, moisture-free, optical grade polycarbonate is injection molded into a high pressure molding machine or press using a stamper. The mold has two parts: one half is the stamper and the other half contains a mirror block to ensure a smooth surface on the CD. Pressed discs, after cooling, are transferred by robot arms to a spindle for the next stage in the process, which is metalization of the active surface of each disc with aluminum by sputtering. The aluminum layer is then protected by a lacquer which is spread as a liquid evenly across the surface of the disc by spin coating. The centrifugal force created by spinning the disc ensures that the lacquer covers the whole disc in an even layer. It is important that the lacquer overlaps the aluminum therefore sealing it from the elements. If left exposed, aluminum will start to oxidize within a few days. The lacquer is then cured by ultra-violet (UV) light. The discs are then ready for label printing using UV cured ink by a flat silk screen process.
Of particular relevance to the present invention is the scale of the structures reliably produced by the above injection molding process. Optical discs with a track pitch of
0
.
8
microns and a pit depth of 0.15 microns are commonly mass produced, with smaller scale structures being produced.
The stamper used in the mold is typically fabricated by exposing a glass substrate coated with a photo-resistive layer to a laser beam. Development of the photo-resist gives a series of pits and lands which are coated with silver or nickel and electroplated to form a master, which is peeled off the glass substrate. This master is then used to form stampers for use in injection molding of the optical disc. In U.S. Pat. No. 5,494,782, incorporated herein by reference in its entirety, Maenza et al. disclose an improved process having many fewer steps which makes use of an excimer or alexandrite laser to remove material from a conducting metal substrate to form the stamper.
An alternative to the injection molding approach for optical disc manufacture is disclosed by Hong in U.S. Pat. Nos. 5,468,324 and 5,635,114. According to this method, a polymer solution is deposited on a master disk, the master is then made to spin and the polymer film dries to form a film having the required thickness, which is then peeled off the master.
Another approach, which is being developed by Sage Technology, Inc., is the NeuROM process, which is the transfer of a CD or similar pattern of features to a continuous web film of metalized polyester using sub-micron scale contact photolithography and the subsequent treatment of that film into a playable machine-read read-only memory storage device. The process consists of several steps including exposure, development, etch and liftoff. The exposed and developed NeuROM film is then bonded to a 1.0 mm film of normal non-birefringent polystyrene, and the completed discs are separated from the laminate film structure using a water knife. This process does not produce the pits and lands of conventional CD manufacture, instead it produces amplitude objects which cause reflection extinction due to absorption, dispersion and diffraction. This means that the interrogating laser beam is not reflected at positions where the metalized film has been etched.
The use of any of the above methods for the fabrication of photoelectric cells or generators is unknown.
Background—Laser Micromachining
Excimer laser micro-machining, which uses lasers which produce relatively wide beams of ultraviolet laser light, is well-known. One interesting application of these lasers is their use in micro-machining organic materials (plastics, polymers, etc.). The absorption of a UV laser pulse of high energy causes ablation, which removes material without melting or distorting the material adjacent to the area machined. The shape of the structures produced is controlled by using a chrome on quartz mask, and the amount of material removed is dependent on the material itself, the length of the pulse, and the intensity of the laser light. Quite deep cuts (hundreds of microns) can be made using the excimer laser. Structures with vertical or tapered sides can be created. Higher powered lasers may be used to ablate metal surfaces.
A further approach is LIGA (Lithographie, Galvanoformung, Abformung). LIGA uses lithography, electroplating, and molding processes to produce microstructures. It is capable of creating very finely defined microstructures of up to 1000 &mgr;m high. The process uses X-ray lithography to produce patterns in very thick layers of photoresist and the pattern formed is electroplated with metal. The metal structures produced can be the final product, however it is common to produce a metal mold. This mold can then be filled with a suitable material, such as a plastic, to produce the finished product in that material. The X-rays are produced from a synchrotron source, which makes LIGA expensive. Alternatives include high voltage electron beam lithography which can be used to produce structures of the order of 100 &mgr;m high, and excimer lasers capable of producing structures of up to several hundred microns high.
BRIEF DESCRIPTION OF THE INVENTION
The present invention discloses cheap and simple processes to manufacture a Photoelectric Generator which will find great utility, particularly in non-concentrator operation. Specifically, disclosed herein are methods for producing, in inexpensive materials using rapid mass production techniques, devices and structures which are substantially similar to those described in my previous disclosure.
Broadly, the invention discloses the fabrication of a radiant energy to electrical power transducer from a transparent first substrate by forming on one face a plurality of channels. The channels are then coated with a photo-emissive material having a work function consistent with the copious emission of electrons at the wavelengths of the radiant energy source used. The first substrate is joined to a second substrate coated with a collector material to which the emitted electrons may travel.
Borealis Technical Limited
Chapman Mark
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