Abstract: Thin semiconductor devices, such as thin solar cells, and a method of fabricating same are disclosed. A microblasting procedure is employed to thin a semiconductor wafer or substrate, such as a solar cell wafer, wherein fine abrasive particles are used to etch away wafer material through a mask. Thick areas remain at the perimeter of the semiconductor device or solar cell, in regions of the semiconductor device or solar cell behind the front interconnect attachment pads, and at corresponding rear interconnect attachment areas. In addition, there are thick areas in a pattern that comprise interconnected beams that support the thin wafer areas. Consequently, predetermined areas of the wafer are thinned to form a predetermined structural pattern in the wafer that includes an external frame and a plurality of interconnected beams.

Abstract: A solar cell assembly is fabricated by adapting efficient microelectronics assembly techniques to the construction of an array of small scale solar cells. Each cell is mounted on an individual carrier, which is a conventional integrated circuit (IC) package such as a dual-in-line package. Electrical connections are made between the cell and the carrier leads by automated wire bonding, followed by the emplacement of an optional secondary solar concentrator element if desired. The carriers are then automatically mounted and electrically connected to a common substrate, such as a printed circuit board, that has its own electrical interconnection network to interconnect the various cells. Finally, a primary concentrator lens assembly is placed over the array of cells. The resulting panel is thin and light weight, inexpensive to produce, allows for any desired interconnection to be made between the cells, and is capable of high conversion efficiencies.

Abstract: In an electrical via structure and fabrication method that is particularly suited to coplanar contact solar cells, an initial opening (38,48a,48b,64) through the substrate is coated and substantially closed with a dielectric material (42,52,80). An inner opening (44) is then formed through the dielectric, and the via is provided with a conductive coating (46,54). The dielectric is initially applied in a liquid state and is thereafter cured to a solid. The need for strong chemical etchants to smooth the via opening prior to application of the dielectric and metallization is eliminated, and a polyimide dielectric on a GaAs/Ge solar cell has resulted in a substantial improvement in leakage resistance and cell efficiency.

Abstract: A photovoltaic microarray such as a solar cell array is monolithically fabricated, without a supporting substrate, by forming a network of trenches from one side of a substrate to define separate cell areas, filling the trenches with an insulative filler material that adheres to the substrate material and provides structural integrity, and then trenching from the opposite side of the substrate to provide an air gap insulation network between adjacent cells. Series connections are provided between adjacent cells by connecting the front surface of one cell over the filler material to the bulk semiconductor for the next cell, with the connection completed through the bulk semiconductor itself to back electrodes for each cell.

Abstract: A photocell (40) includes a photovoltaic or otherwise photosensitive layer structure (44) on which a passivation or window layer (52) of an environmentally sensitive material such as aluminum gallium arsenide (AlGaAs) and an antireflection (AR) coating (54) are formed. An electrically conductive cap layer (60) delineated in a front contact grid configuration sealingly extends through the AR coating (54) to the window layer (52). An ohmic metal contact (64) is evaporated over and seals the cap layer (60) and the contiguous areas of the AR coating (54). The contact grid interface at which the cap layer (60) contacts the window layer (52) is sealed by the AR coating (54) and the contact (64). The photocell (40) is fabricated by forming, delineating and etching the cap layer (60), forming the AR coating (54) and then forming the contact (64) by evaporation of metal.

Abstract: A pattern of current collection gridlines (24) is formed on a surface (20) of a photovoltaic wafer (12). An ohmic contact strip (28) is formed adjacent to an edge (12c) of the wafer (12) in electrical interconnection with the gridlines (24). Interconnect tabs (30) are integrally formed with the gridlines (24) and contact strip (28), extending away from the contact strip (28) external of the edge (12c) for series or parallel interconnection with other solar cells. The interconnect tabs (30) may have a stress reflief configuration, including a non-planar bend or loop. The wafer (12) initially has a first portion (12a) and a second portion (12b). A barrier layer (50) of photoresist or the like is formed on the second portion (12b). The grid (24) and contact strip (28) are formed on the first portion (12a) simultaneously with forming the interconnect tabs (30) over the barrier layer (50 ) on the second portion (12b) using photolithography and metal deposition.

Abstract: A photoresponsive layer formed of a semiconductive material such as gallium arsenide has differently doped strata which define a junction therebetween, and generates a photovoltaic effect in response to light incident on a front surface thereof. A front electrode is formed on the front surface. A structurally supporting back electrode open conductive support or grid structure is formed on a back surface of the photoresponsive layer. The support structure is sufficiently thick, approximately 12 to 125 microns, to prevent breakage of the photoresponsive layer, which may be as thin as approximately 25 to 100 microns. The support structure has a pattern selected to prevent propagation of a crack through the photoresponsive layer thereof.

Abstract: A solar cell is disclosed wherein both the emitter and the base electrical contacts for a solar cell are disposed on the back major surface. Holes extend through the back major surface and the base layer to the emitter layer. The walls of the holes are doped to the same conductivity as the front emitter layer. Emitter contacts are deposited on the back major surface of the cell and extend into the holes making electrical contact to the emitter layer for collecting light generated current carriers. The base contacts are also disposed on the back major surface, and antireflection coatings are deposited on the emitter front major layer. Consequently, the front of the solar cell can be made smooth and therefore, a specularly reflective (non-scattering) solar cell results.

Abstract: A system for protecting a radiation-responsive device, such as an infrared sensor in an imaging system includes a plasma switch operative in response to amplitude of incident radiation. The protection system is suitable for protecting the infrared sensor from a high-intensity laser beam which might impinge upon receiving optics of the imaging system. The plasma switching responds differently to different portions of the electromagnetic spectrum, a lower frequency portion being either transparent or reflective of the infrared radiation, while an upper frequency portion absorbs radiation to initiate a high or low density of free-charge carriers in the plasma dependent on the intensity of photons injected into the plasma in the higher frequency band.

Abstract: Disclosed herein is a solar converter structure and fabrication process therefor which includes a composite zinc selenide fluorescent wavelength shifter (FWS) prepared with anti-reflective (AR) coatings on both major surfaces thereof. One of these AR coatings is adhesively bonded to an AR coating on the sunlight-receiving surface of a gallium arsenide or an aluminum gallium arsenide photovoltaic (PV) solar cell, and the "free-standing" FWS composite wavelength shifter protects the solar cell from proton and ultraviolet radiation damage. The ZnSe wavelength shifter has a spectral response below about 0.47 micrometers and the solar cell has a spectral response above about 0.47 micrometers. The wavelength shifter absorbs radiation in the 0.3 to 0.47 micrometer range and re-emits radiation to the solar cell in a band centered about 0.62 micrometers and well within the pn junction response spectra for the solar cell to thereby enhance its power output.

Abstract: A method for providing deep impurity doped regions under the back contacts of a solar cell. In a semiconductor wafer with a p-n junction therein defining an n+ layer emitter and p-type layer bulk, a p+ layer is formed in the p-type layer under the back surface of the wafer. An oxide passivation layer is disposed over the back surface. Metal paste is screen printed onto the oxide layer in a predetermined pattern. The combination is heated to a temperature such that the metal paste will drive through the oxide layer and alloy with selected regions of p+ layer and p-type layer to a predetermined depth forming heavily doped p+ impurity regions. Metallization is applied onto the oxide layer making electrical contact with the heavily doped p+ impurity regions.

Abstract: A gallium arsenide solar cell is disclosed which employs a front aluminum gallium arsenide window layer. Metallic grid lines for charge carrier collection traverse the window layer and extend through this layer to the emitter layer. A flat conductive bar on the window layer crosses and makes electrical contact with the metallic grid lines. A flat metallic strip located on the window layer near an edge is spaced from the grid lines and conductive bar but is electrically coupled to the conductive bar by metallic bridges. Since the metallic strip is not in contact with the grid lines, external electrical connections can be affixed to the flat metallic strip using high temperature welding or soldering techniques without damage to the semiconductor body.

Abstract: A gallium arsenide solar cell is disclosed having an aluminum gallium arsenide window layer in which fine metallic contact lines extend through the aluminum gallium arsenide window to electrically contact the emitter layer, and a plurality of metallic grid lines disposed on the window layer cross the contact lines, thereby making electrical contact to the metallic contact lines. A flat metallic strip extending along one of the edges of the solar cell electrically couples the grid lines to one another. Consequently, two separate metals can be used, one with good ohmic contact properties for the grid lines and another with good adhesion and current conducting properties for the current collecting bars. Additionally, the metallic contacts lines can be made very narrow to reduce the contact area to the emitter thereby reducing the recombination current in the emitter.

Abstract: A focusing multi-point high-concentrator optical system is disclosed. The system is useful for concentrating energy such as solar radiation for use in solar energy conversion systems. The configuration of the optical system incorporates thin metallized Fresnel reflector elements applied to panels formed into focusing surfaces having a common axis. The Fresnel elements are oriented axially to the axis of the focusing surfaces. The optical configuration produces a substantially rectangular focal zone centered over each panel. For a plurality of panels of a given width, there will be a plurality of focal zones, each separated by a distance equivalent to the panel width. At least one energy absorber is maintained substantially at each focal zone and may comprise a photovoltaic cell, thermal absorber, etc. and combinations thereof.