Photon Power, Inc.

D. H. Baldwin Company

Other

Curtis M Lampkin

John F Jordan

Guy A Roderick

Peter Locke

John P Jordan

Robert B Nikodem

An apparatus is described for depositing a thin film (9) of compound materials on selected substrates (48) in an evacuable coating chamber. This apparatus includes a rotating primary surrogate magnetron cathode surface (19) which acts to receive, in-situ, material to be sputtered. Vapor crucibles (2) expose the rotating cathode surface (19) to material vapors (8) which condense on the thermally cooled cathode surface (19) to combine with other coatings on the cathode and are thence rotated through the associated plasma sputter zone (26P) to sputter deposit desired film (9). Auxiliary rotating magnetron cathodes (32) can deposit additional material onto rotating primary cathode (19). Molten material crucible assemblies (31) having coating rollers (34) can convey molten material onto rotating auxiliary thermally cooled cathode surfaces (32) which sputter coat primary cathode. When a selected combination of vapor crucibles (2) and auxiliary rotating cathodes (32) cooperate to coat rotating primary cathode surface (19) it is possible to deposit alloys or a large class of compound thin film materials in-situ without having to prefabricate cathodes of compound materials. Sputter deposited film (9) uniformity is improved by use of three methods: cyclically varying power applied to the primary surrogate cathode, narrow sputter zones, and premixing of condensing vapors.

Magnetron sputtering method and apparatus for compound thin films

An improved spray booth is provided for use in forming high quality thin films by controlling the spray parameters related to film formation. A spray nozzle design is selected which permits control of the spray footprint on a heated substrate. A projected atomized liquid is formed to the selected spray configuration by directing spray cones of air toward the atomized liquid. Dwell time of the spray material adjacent the hot substrate is then controlled by controlling the velocity of airflow within the spray chamber and adjacent the substrate. To promote a gas phase reaction, a roof section is provided with reduced airflow wherein sufficient dwell time is provided for the vapor reaction to occur. Where a liquid phase reaction is provided, high velocity airflow is maintained to promptly remove reaction products and spray material which has not reached the surface after a selected time period. The spray booth is designed for frequent cleaning by providing separately removable sections where the frequency of cleaning may be varied as a function of the accumulated condensate. Thus, regions of the spray booth in contact with the sprayed solution may be removed without removing the entire spray booth. Particular uses employing the particular design principles include application of a film of SnO.sub.x which is highly transparent and electrically conductive and thin films of CdS suitable for use in forming large area photovoltaic panels.

Spray forming thin films

A photovoltaic cell having an electrically conductive substrate, which may be glass having a film of conductive tin oxide; a first layer containing a suitable semiconductor, which layer has a first component film with an amorphous structure and a second component film with a polycrystalline structure; a second layer forming a heterojunction with the first layer; and suitable electrodes where the heterojunction is formed from a solution containing copper, the amorphous film component is superposed above an electrically conductive substrate to resist permeation of the copper-containing material to shorting electrical contact with the substrate. The penetration resistant amorphous layer permits a variety of processes to be used in forming the heterojunction with even very thin layers (1-6.mu. thick) of underlying polycrystalline semiconductor materials. In some embodiments, the amorphous-like structure may be formed by the addition of aluminum or zirconium compounds to a solution of cadmium salts sprayed over a heated substrate.

Polycrystalline photovoltaic cell

An improved conveyor assembly is provided for transporting a transparent vitreous substrate along a group of controlled radiative heaters. A plurality of control groups are formed from the radiative heaters and the illumination for the various control groups is isolated so that areas of the conveyor or substrate are illuminated by only a single control group at any one time. Heater control thermocouples are affixed to the radiative heater elements and the output signals from the control thermocouples are calibrated from a calibration thermocouple extending to a position between the control thermocouple and the substrate surface. A wire mesh belt assembly permits illumination of the substrate through the conveyor assembly while supporting the substrate in a manner effective to obtain uniform heating of the substrate. A chain-type system is used for moving the supports of the wire mesh belt and end drum portions of the conveyor are configured to accommodate any difference in radius of travel between the mesh belt and the support bars as the assembly rotates about the end drums.

Heated conveyor system

An array of photovoltaic cells in a back wall-type configuration supported by a rigid transparent vitreous substrate, such as glass, for admitting incident radiation to the cells. A plurality of cells are interconnected into a desired electrical configuration by one or more layers of electrically conducting materials which overlie the entire heterojunction of each cell to minimize the internal resistance of the cell and may conveniently protect the heterojunction from degrading environmental conditions. Various component layers forming the photovoltaic cells are selectively removed and strips of insulating material are applied prior to forming the heterojunction. The electrically conductive material is thereafter applied and separated at areas protected by insulating material. The resulting series array contains no exposed heterojunction areas, thereby obtaining improved operating stability and performance.

Solar cell array

Methods and apparatus are provided for forming films of materials which are component layers of solar energy conversion devices, e.g. photovoltaic cells and heat collector panels. A selected substrate, generally glass, is heated while being sprayed with solutions which react on the heated surface to form a particular film. Films of SnO.sub.x and CdS are particularly produced. According to the present invention, a thermal energy input gradient is provided to approximate the energy loss gradient during the spray process. Radiative heaters provide a rapid resupply of energy to the substrate and, in some instances, directly to the film forming surface. Temperature detectors, such as thermocouples, monitor substrate temperature to provide the radiative energy input needed for substantial temperature uniformity.

Apparatus for quality film formation

A photovoltaic cell having an electrically conductive substrate, which may be glass having a film of conductive tin oxide; a first layer containing a suitable semiconductor, which layer has a first component film with an amorphous structure and a second component film with a polycrystalline structure; a second layer forming a heterojunction with the first layer; and suitable electrodes where the heterojunction is formed from a solution containing copper, the amorphous film component is superposed above an electrically conductive substrate to resist permeation of the copper-containing material to shorting electrical contact with the substrate. The penetration resistant amporphous layer permits a variety of processes to be used in forming the heterojunction with even very thin layers (1-6.mu. thick) of underlying polycrystalline semi-conductor materials. In some embodiments, the amorphous-like structure may be formed by the addition of aluminum or zirconium compounds to a solution of cadmium salts sprayed over a heated substrate.

Photovoltaic cell

A large area photovoltaic cell comprising a layer of polycrystalline cadmium sulfide, about 1 to 2 microns thick, formed by simultaneously spraying two suitably selected compounds on a uniformly heated plate of Mesa glass and irradiating the layer of polycrystalline cadmium sulfide with intense ultra-violet light during the spraying.

A method of producing an array of photovoltaic cells responsive to incident radiation by forming heterojunction-forming material layers over a transparent substrate panel having a transparent electrically conductive coating and thereafter removing selected portions of the materials to form a plurality of cells on a common substrate. The cells are then electrically interconnected by depositing electrically conducting materials over substantially the entire panel and removing only those portions of the deposited materials required to form series electrical connections.

Method of making a solar cell array

An array of photovoltaic cells in a back wall-type configuration supported by a rigid transparent vitreous substrate, such as glass, for admitting incident radiation to the cells. A plurality of cells are interconnected into a desired electrical configuration by one or more layers of electrically conducting materials which overlie substantially the entire heterojunction of each cell to minimize the internal resistance of the cell and may conveniently protect the heterojunction from degrading environmental conditions. The conducting layer interconnects an exposed electrode region of one cell with the heterojunction forming material of the adjacent cell while remaining insulated from any intervening cell structure. In one embodiment, the uppermost conducting layer is lead, which seals the underlying materials from atmospheric constituents, such as oxygen and water vapor, while remaining relatively inert to such constituents.

Methods and apparatus are provided for forming films of materials which are component layers of solar energy conversion devices, e. g. photovoltaic cells and heat collector panels. A selected substrate is heated while being sprayed with solutions which react on the heated surface to form a particular film. Films of SnO.sub.x and CdS are particularly produced. According to the present invention, the spray is projected at an angle to control upstream flow and confine film formation to the substrate panel portions most suitable for forming the selected film. Various waste products are removed to minimize defects in the resulting film. Baffles are located to shield the substrate surface at selected areas and preclude the spray from impacting on the shielded areas.

Method for quality film formation

A photovoltaic cell having an electrically conductive substrate, which may be glass having a film of conductive tin oxide; a first layer containing a suitable semiconductor, which layer has a first component film with an amorphous structure and a second component film with a polycrystalline structure; a second layer forming a heterojunction with the first layer; and suitable electrodes where the heterojunction is formed from a solution containing copper, the amorphous film component is superposed above an electrically conductive substrate to resist permeation of the copper-containing material to shorting electrical contact with the substrate. The penetration resistant amorphous layer permits a variety of processes to be used in forming the heterojunction with even very thin layers (1-6.mu. thick) of underlying polycrystalline semi-conductor materials. In some embodiments, the amorphous-like structure may be formed by the addition of aluminum or zirconium compounds to a solution of cadmium salts sprayed over a heated substrate.

A large area photovoltaic cell comprising a layer of multicrystalline cadmium sulfide, about 1 to 2 microns thick, formed by simultaneously spraying two suitably selected compounds on a uniformly heated plate of Nesa glass, thereafter forming a coating of Cu.sub.2 S over the cadmium sulfide layer while the latter is heated, to form a photovoltaic heterojunction, applying thereover a layer of CuSO.sub.4, and applying electrodes of Cu and Zn, respectively, to separated areas of the layer of CuSO.sub.4, and heating the cell to form a cuprous oxide rectifying junction under the copper electrode by reaction of the Cu electrode with the CuSO.sub.4, while diffusing the zinc through the body of the cell. The diffusion of the zinc provides a negative electrode coplanar with the positive copper electrode, eliminating any need for introducing mechanically complex provision for making a connection to the Nesa glass, while the use of a CuSO.sub.4 --Cu combination enables use of a layer of CdS only 1 to 2 microns thick, rather than the usual 20 microns, despite the fact that such thin layers tend to have pinholes, which in the prior art render the cells inoperative, but in the present teaching do not.

A method of forming a cadmium sulfide film from a solution containing a cadmium salt and a sulfur containing compound comprising inclusion of a chlorine containing compound in the solution utilized to form the cadmium sulfide film.

Growing community of inventors

El Paso, TX, United States of America

Curtis M Lampkin