DE102014010701A1 - Solar power system for an aircraft, a water powered device or vehicle or land vehicles using inverted metaphorical multi-junction solar cells - Google Patents

Abstract

A system for generating electrical power from solar radiation using a thin layer III-V compound multi-junction semiconductor solar cell mounted on a carrier in a non-planar configuration is an airplane, a watercraft, or a land vehicle.

Description

Background of the invention

1. Field of the invention

The present invention relates generally to solar power systems for the conversion of sunlight into electrical energy, and more particularly to the use of III-V compound semiconductor solar cells.

2. Description of Related Art

Commercially available silicon solar cells for terrestrial solar power applications have efficiencies ranging from 8% to 15%. Compound or compound semiconductor solar cells based on III-V compounds have 28% efficiency under normal operating conditions and 32.6% in concentration. In addition, it is known that the concentration of solar energy on photovoltaic cells increases the efficiency of the cells.

Terrestrial solar power systems currently use silicon solar cells in view of their low cost and wide availability. Although compound semiconductor solar cells have been widely used in satellite applications where their power-to-weight efficiencies are more important than the cost per watt considerations in selecting such devices, such solar cells have not been designed and configured for terrestrial systems, nor have terrestrial solar power systems been configured and optimized for use with compound semiconductor solar cells.

In conventional solar cells constructed with silicon (Si) substrates, an electrical contact is typically disposed on a light absorbing side or front side of the solar cell and a second contact is placed or disposed on the back of the cell. A photoactive semiconductor is disposed on the light absorbing side of the substrate and has one or more p-n junctions which produce an electron flux when light is absorbed within the cell.

The contact on the face of the cell where light enters is generally expanded in the form of a grid pattern over the surface of the front and is generally made of a good conductor such as metal. The grid pattern does not have to cover the entire face of the cell because grid materials, although good electrical conductors, are generally not transparent to light.

The grid pattern on the face of the cell is generally widely spaced to allow light to enter the solar cell, but not to the extent that the electrical contact layer has difficulty in collecting the current generated by the flow of electrons in the cell. The rear electrical contact has no such diametrically opposed limitations. The back or back contact operates simply as an electrical contact and typically covers the entire back surface or back surface of the cell. Since the back contact must be a very good electrical conductor, it is almost always formed from a metal layer.

The arrangement of both anode and cathode contacts on the back of the cell simplifies the interconnections of individual solar cells in a horizontal arrangement in which the cells are electrically connected in series. The back contact constructions are known from the PCT patent publication WO 2005/076960 A2 by Gee et al. for Silicon Cells and U.S. Patent Application No. 11 / 109,016 filed April 19, 2005 for compound semiconductor solar cells.

Another aspect of the terrestrial solar power system is the use of concentrators (such as lenses and mirrors) to focus the incident sunrays onto the solar cell or solar cell array. The geometric design of such systems also requires a solar tracking mechanism which allows the plane of the solar cells to continuously point to the sun as the sun passes through the sky during the day, optimizing the amount of sunlight impinging on the cell.

Another aspect of the concentrator or concentrator-based solar power cell configuration design relates to the design or layout of the heat distribution structures or the coolant techniques for the distribution of heat generated by intense light impinging on the surface of the semiconductor body. Prior art designs as described in the PCT publication WO 02/080286 A1 of 10 October 2002 use a complicated coolant flow path in thermal contact with the photovoltaic (silicon) cells.

Another aspect of a solar cell system is the physical structure of the semiconductor material that forms the solar cell. Solar cells are often fabricated in vertical multi-junction (multi-junction) structures and arranged horizontally with the individual solar cells electrically connected in series. The shape and structure of an array as well as the number of cells it contains are determined in part by the desired output voltage and the desired output current. One type of multi-junction structure useful in the construction according to the present invention is inverted metamorphic solar cell structures such as those disclosed in U.S. Pat U.S. Patent No. 6,951,819 (Iles et al.) And also in the reference MW Wanless et al, Lattice Mismatched Approaches for High Performance, III-V Photovoltaic Energy Converters (Conference Proceedings of the 31st IEEE Photovoltaic Specialists Conference, Jan. 3-7, 2005, IEEE Press, 2005) ; and further reference is made to published US Patent Application No. 2007/0277873 A1 (Cornfeld et al.) and incorporated herein by reference.

Summary of the invention

1. Objects of the invention

It is an object of the present invention to provide an improved multi-junction solar cell or multiple solar cell.

It is a further object of the invention to provide a solar cell which is thin and flexible and adapts to a non-planar support.

Some implementations or embodiments may possibly achieve less than all of the above goals.

2. Features of the invention

Briefly and in general terms, the invention provides an aircraft, a watercraft or a land vehicle, comprising: a non-planar support for mounting a plurality of solar cells; and a plurality of solar cells mounted on the non-planar support, each solar cell of the plurality of solar cells being capable of bending to conform to the non-planar surface of the non-planar support, and each solar cell the plurality of solar cells comprises a semiconductor body in the form of a thin flexible film formed of III-V compound semiconductors including: a first solar subcell having a first band gap; a second solar subcell arranged above the first subcell and having a second bandgap smaller than the first bandgap; a grading intermediate view constructed of InGaAlAs and disposed over the second subcell in said body and having a third bandgap greater than the second bandgap; and a third solar subcell over said interlayer in the body and lattice mismatched with respect to the second subcell and with a fourth bandgap smaller than the third bandgap; wherein on the non-planar support, the plurality of solar cells is mounted, and this is mounted on the aircraft, the watercraft or the land vehicle.

According to another aspect of the present invention, there is provided a solar cell device including: a non-planar support for mounting a plurality of solar cells; and a plurality of solar cells mounted on the non-planar support, each solar cell of the plurality of solar cells being capable of bending so as to correspond to the non-planar surface of the non-planar support, and each solar cell of that plurality of solar cells comprises a thin, flexible film semiconductor body formed of III-V compound semiconductors, including: a first solar subcell having a first bandgap; a second solar cell disposed over the first solar cell and having a second band gap smaller than the first band gap; a grading interlayer composed of InGaAlAs and disposed over the second subcell in said body and having a third bandgap greater than the second bandgap; and a third solar subcell over said interlayer in said body, lattice mismatched with respect to said second subcell, and further having a bandgap less than the third bandgap; wherein the solar cell assembly is mounted on an aircraft, a watercraft or a land vehicle. In some embodiments, the non-planar or non-planar support has a curved surface.

According to a further aspect, the invention provides a method for mounting a plurality of solar cells on an aircraft, a watercraft or a land vehicle, the method comprising: providing a non-planar support for mounting a plurality of solar cells; Mounting the plurality of solar cells on the non-planar support, each solar cell of the plurality of solar cells being capable of bending in such a way as to correspond to a non-planar or non-planar surface of the non-planar support, and wherein each solar cell of the plurality of solar cells has a thin flexible film semiconductor body formed of III-V compound semiconductors including: a first solar subcell having a first band gap; a second solar subcells disposed above the first subcell and at a second bandgap smaller than the first bandgap; a grading interlayer composed of InGaAlAs and disposed over the second subcell in said body and having a third bandgap greater than the second bandgap; and a third solar cell over said interlayer in said body and lattice mismatched with respect to said second subcell and with a fourth bandgap smaller than said third bandgap; and attaching the non-planar support having the plurality of solar cells mounted thereon to an airplane, a watercraft, or a land vehicle. In some embodiments, the non-planar or non-planar support is suitable for attachment to a curved surface of the aircraft, watercraft, or land vehicle.

Some implementations or embodiments of the invention may use only some of the above aspects.

Brief description of the drawings

1 Fig. 12 shows a cross-sectional view of an inverted metamorphic solar cell which can be used in the present invention.

2 is a simplified cross-sectional view of an embodiment of an electrical interconnection between solar cell 500 and solar cell 600 , similar to the solar cell illustrated in 1 , after additional processing steps;

3 and 4 illustrate embodiments in which a solar cell array as in 2 illustrated attached to a carrier having a non-planar surface which in turn is attached to an aircraft, a watercraft or a land vehicle;

5 Figure 4 is a perspective view of one embodiment of a watercraft with a solar array mounted on a non-planar surface of the watercraft;

6 Figure 3 is a perspective view of an exemplary embodiment of an aircraft with a solar array mounted on a non-planar surface of the aircraft; and

7 and 8th FIG. 12 are perspective views of exemplary embodiments of land vehicles with solar assemblies mounted on non-planar surfaces of the land vehicle.

Other objects, advantages, and novel features of the present invention will become apparent to those skilled in the art from this disclosure, including the following detailed description, as well as the practice of the invention. Although the invention will be described below with reference to illustrative embodiments, it is to be understood that the invention is not so limited. Those skilled in the art having access to the teachings of the present invention will recognize additional applications, modifications and embodiments in other fields which are within the scope of the disclosed invention and claimed herein with respect to which the invention may be useful.

Description of illustrative embodiments

Details of the present invention will now be described, including exemplary aspects and embodiments thereof. With reference to the drawings and the following description, like reference numerals are used to designate similar or identical or functionally similar elements, and the description illustrates key features of exemplary embodiments in a highly simplified schematic manner. Moreover, the drawings are not intended to illustrate each feature of the actual embodiment nor the relative dimensions of the elements shown, which are also not shown to scale.

The present invention relates generally to solar power systems for converting sunlight into electrical energy using III-V compound semiconductor solar cells.

1 shows the inverted multi-junction metamorphic solar cell that can be used in one embodiment of the present invention, including three subcells A, B, C. More particularly, the solar cell is constructed using the method of US Patent Application Publication No. 2007/0277873 A1 (Cornfeld et al.). As shown in the figure, the upper surface (top) of the solar cell has grid lines 501 on that directly above the contact layer 105 are separated. A non-reflective or antireflective (ARC) dielectric layer 130 is deposited over the entire surface of the solar cell. An adhesive is deposited over the ARC layer for attachment to a cover glass. The solar cell structure has a window or window layer 106 adjacent to the contact layer 105 on. Subcell A, consisting of an n + emitter layer 107 and a p-type base layer 108 is then on the window layer 106 shaped.

In one embodiment, the n + -type emitter layer becomes 107 composed of InGa (Al) P, and the base layer 108 is built up from InGa (Al) P.

Adjacent to the base layer 108 is a back surface field ("BSF") layer 109 deposited, which is used to reduce the recombination loss. The BSF layer 109 drives the minority carriers from the zone near the base / BSF interface surface to minimize the effect of recombination loss.

On the BSF layer 109 is a sequence of heavily-doped p-type and n-type layers 110 deposited, which form a tunnel diode, a circuit element which has the function of electrically connecting cell A to cell B.

On the tunnel diode layers 110 is a window or window layer 111 deposited. The window layer 11 used in subcell B also works to reduce recombination loss. The window layer 111 also improves the passivation of the cell surface of the underlying junctions or junctions or transitions. One skilled in the art will recognize that one or more additional layers may be added or deleted from the cell structure without departing from the scope of the invention.

On the window layer 111 cell B has the following deposited: the emitter layer 112 and the p-type base layer 113 , These layers are preferably constructed of InGaP and In _0.015 GaAs, respectively, in one embodiment, although any other suitable materials could also be used according to lattice constant and bandgap requirements.

On cell B is a BSF layer 114 deposited, which performs the same function as the BSF layer 109 , A p ++ / n ++ tunnel diode 115 is above the BSF layer 114 deposited, similar to the layers 110 , wherein in turn a circuit element is formed, which serves here for the electrical connection of the cell B with the cell C. A buffer layer 115a , preferably InGaAs, is above the tunnel diode 115 deposited and has a thickness of 1.0 micron. A metamorphic buffer layer 116 is above the buffer layer 115a deposited, which is preferably a compositionally graded InGaAlAs series of layers with monotonic changing lattice constant, to achieve a transition for the lattice constant from cell B to subcell C. The band gap of the layer 116 is 1.5 ev constant with a value slightly larger than the bandgap of the center cell B.

In one embodiment, as in the Wanless et al. In the literature reference, the grading step contains nine compositionally graded steps, each step layer having a thickness of 0.2 microns. In one embodiment, the interlayer is constructed of InGaAlAs with a monotonic changing lattice constant such that the bandgap remains constant at 1.0 ev.

Above the metamorphic buffer layer 116 there is a window layer 117 composed of In _0.78 GaP, followed by a subcell C with an n + emitter layer 118 and a p-type base layer 119 , These layers are preferably constructed of In _0.30 GaAs in one embodiment.

A BSF layer 120 is above the base layer 119 deposited. The BSF layer 120 performs the same function with respect to cell C as the BSF layers 114 and 109 ,

A p + contact layer 121 is over BSF layer 120 deposited and a metal contact layer 122 , preferably a sequence of Ti / Au / Ag / Au layers is over layer 121 applied.

Generally speaking, the solar cell array is a thin film semiconductor body including a multijunction solar cell, which in some embodiments has first and second electrical contacts on the back surface thereof. The module includes a support for mounting the solar cell and providing electrical contact with the first and second contacts.

2 is a cross-sectional view of an embodiment with an electrical interconnection between solar cell 500 and solar cell 600 similar to the one in 1 illustrated solar cell, after additional processing steps. 2 is a simplified drawing showing a few of the upper layers and lower layers of the solar cell as in 1 shown shows. In the solar cell 500 is a contact pad or contact terminal 520 to the grid metal layer 501 shown, close to the adhesive layer 513 and the cover glass 514 , The adhesive or adhesive layer and the cover glass 614 are also in the solar cell 600 shown. The cover glasses 514 and 614 are at the top of the solar cells 500 and 600 fastened, by adhesive 513 respectively. 613 , cover glasses 514 and 614 are typically about 4 mils thick. Although the use of a cover glass is desirable in many environmental conditions and applications, it is not necessary for all implementations, and additional layers or structures may also be used to provide additional solar cell support or environmental protection.

Metal films or layers 125 and 625 are at the metal contact layers 122 and 622 attached, using a link layer 124 and 624 for the solar cells 500 respectively. 600 , In one embodiment of the present disclosure, the interconnect layers are 124 and 624 Adhesives such as polyimides (for example, a carbon-loaded polyimide) or epoxies (for example, a B-stage epoxide). In further embodiments of the invention, the interconnect layers 124 and 624 Solders such as AuSn, AuGe, PbSn or SnAgCu. The solder may be a eutectic solder.

In some embodiments, the metal films or layers are 125 and 625 solid or solid metal foils. In some implementations, the metal films are 125 and 625 solid metal foils, with adjacent layers of polyimide material such as Kaptom ^™ . More generally, the material may be a nickel-cobalt-iron alloy material or a nickel-iron alloy material. In some implementations, the metal films 125 and 625 a molybdenum layer on.

In some implementations, the metal films have 125 and 625 a thickness of approximately 50 microns, or more generally between 0.001 and 0.01 inches. An alternative substrate implementation would be 0.002 inch Kapton film plus 0.0015 inch adhesive / 0.002 inch Mo foil / 0.02 inch Kapton film plus 0.0015 inch adhesive for a total thickness of 0.009 inches. However, the Kapton film can be as thin as 0.01 inches and as thick as 0.1 inches. The adhesive may be as thin as 0.0005 inches and as thick as 0.005 inches. The Mo film can be as thin as 0.001 inches and as thick as 0.005 inches.

2 Fig. 3 is an illustration of the attachment of an inter-cell electrical connection 550 in one embodiment of the present disclosure. The electrical interconnection 550 is generally serpentine. The first end part is typically at the contact 520 welded, although other methods of connection could also be used. The electrical interconnection 550 further comprises a second U-shaped part 552 connected to the first part, which extends over the top surface or top and edge 510 the cell extends; a third straight part 553 is connected to a second part and extends vertically parallel to the edge of the solar cell and the side edge of the cell and terminates in a bent contact end part 554 below the bottom surface of the cell, which is orthogonal to the third part 553 extends. The contact end part 554 is suitable for direct contacting of the ground contact or connection of the first polarity of the adjacent second solar cell 600 ,

The intermediate link 550 may be composed of molybdenum, a nickel-cobalt-iron alloy material such as Kovar ^™ or a nickel-iron material such as Invar ^™, and may have a substantially rectangular shape with a thickness between 0.0007 and 0.0013 inches.

One aspect of the present invention is shown in FIG 3 is that the solar cell array a variety of flexible thin-film or thin-film solar cells 400 . 500 . 600 . 700 and 800 having, connected to electrical interconnections 450 . 550 . 650 and 750 , The solar cell assembly may be shaped to be on the surface of the carrier 1002 corresponds, which has a non-planar or non-planar configuration. The carrier 1002 may be attached to the surface of an aircraft, a watercraft or a land vehicle, using an adhesive (adhesive) 1001 ,

4 is an expanded view of the solar cell array of the 3 and more clearly shows the curved surface formed by the solar cells attached to the carrier, which in turn is attached to the aircraft, vessel or land vehicle.

Solar cell arrangements as in the 3 and 4 For example, they may be attached to a non-planar surface of an aircraft, a watercraft, or a land vehicle. Exemplary aircraft, watercraft, or land vehicles may or may not have drivers (eg, drones).

Exemplary aircraft with nonplanar surfaces include aerostats (lighter than air) and aerodyne (heavier than air). Exemplary aerostats may be, for example, non-driven structures (eg, balloons such as hot air balloons, helium balloons and hydrogen balloons) and powered devices (such as airships or conceivable aircraft). Exemplary aerodyne may be, for example, non-powered structures (eg, kites and paragliders) and powered devices (eg, airplanes and helicopters). Exemplary aerodyne may be fixed wing devices (eg, aircraft and gliders) or rotary powered devices (eg, helicopters and autogyros).

Exemplary watercraft with non-planar surfaces may be motorized or non-motorized and may be powered or just floating. Exemplary craft may be surface equipment (eg, ships, boats and hovercraft) and submersible Devices (eg submarines or submerged devices).

Examples of land vehicles having non-planar surfaces may be motorized (eg automobiles, trucks, buses, motorcycles, rovers and trains) or non-motorized (eg bicycles).

5 FIG. 12 is a perspective view of an example of an embodiment of a watercraft. FIG. The submersible watercraft 904 has a non-flat surface and is attached to the platform 903 over a rope 902 , The submersible or submersible vessel 904 includes the underwater float tank 901 which is maintained at a desired depth below the water surface by controlling the length of the rope 902 , The solar cell arrangement 900 is at the non-level surface of the underwater booby 901 appropriate. In certain embodiments, when light is on the solar cell array 900 of the submersible watercraft 904 Electricity can be generated by the solar cell arrangement 900 is generated at the platform 903 be provided, via the rope 902 ,

6 FIG. 12 is a perspective view of an exemplary embodiment of an aircraft. FIG. The plane 1000 has a non-flat surface and is a container with a fixed wing. The solar cell array 1001 is at the non-level surface of the wing of the aircraft 1000 appropriate. In certain embodiments, when light is on the solar cell array 1001 of the plane 1000 impinges, electrical power generated by the solar cell array 1001 for the operation of the systems (for example navigation systems, propulsion systems and the like) of the aircraft 1000 to be delivered.

7 FIG. 12 is a perspective view of an exemplary embodiment of a land vehicle. FIG. land vehicle 2000 has a non-flat surface and is an automobile. The solar cell arrangement 2001 is at the non-level surface of the automobile 2000 appropriate. In certain embodiments, when light is on the solar cell array 2001 of the automobile 2000 impinges, electrical power generated by the solar cell array 2001 provided for the operation of systems (for example navigation systems, drive systems and the like) of the automobile 2000 , In certain embodiments, the automobile is 2000 a hybrid powered or electrically powered automobile.

8th FIG. 13 is a perspective view of another exemplary embodiment of a land vehicle. FIG. The land vehicle 3000 has a non-planar surface and is a rover that can be used for land navigation and / or exploration on Earth or other planets. The solar cell arrangement 3001 is at a non-level surface of the rover 3000 appropriate. In certain embodiments, when light is on the solar cell array 3001 of the rover 3000 impinges, electrical power generated by the solar cell array 3001 in the operation of systems (such as navigation systems, propulsion systems and the like) of the rover 3000 be used. In certain embodiments, the rover is 3000 a hybrid or electric powered land vehicle.

Although the invention has been described in certain specific embodiments, additional modifications and changes may be made by those skilled in the art. The present invention is therefore considered in all respects to be illustrative and not restrictive. The scope of the invention is indicated by the appended claims, and all changes within the meaning and range of equivalents are intended to be embraced therein.

It will be understood that each of the elements described above, or two or more together, may also find useful application in other types of constructions different from those described above.

Although the invention has been illustrated and described as being embodied in a solar power system using III-V compound semiconductors, it is not intended to limit the details shown, as various modifications and structural changes can be made without departing from the scope of the invention.

Without further analysis, the foregoing description discloses the object of the present invention, which may be readily adapted from others using known knowledge for various applications without omitting features, in view of the state of the art, that is, features that are fair to essential characteristics of the art general or specific aspects of the invention and, therefore, such adaptations should be encompassed by the scope of the invention as defined by the following claims.

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• WO 2005/076960 A2 [0007]
• WO 02/080286 A1 [0009]
• US 6951819 [0010]

Cited non-patent literature

• MW Wanless et al, Lattice Mismatched Approaches for High Performance, III-V Photovoltaic Energy Converters (Conference Proceedings of the 31st IEEE Photovoltaic Specialists Conference, Jan. 3-7, 2005, IEEE Press, 2005). [0010]
• Wanless et al. [0034]

Claims (10)

An aircraft, watercraft or land vehicle, comprising: a non-planar support for mounting a plurality of solar cells; and a plurality of solar cells mounted on the nonplanar support, each solar cell of the plurality of solar cells being capable of bending so as to correspond to the nonplanar surface of the nonplanar support, and wherein each solar cell is of the plurality of solar cells Solar cells comprises a thin, flexible film semiconductor body formed of III-V compound semiconductors, including: a first solar subcell having a first band gap; a second solar subcell disposed above the first subcell and having a second bandgap smaller than the first bandgap; a grading interlayer composed of InGaAlAs and disposed over the second subcell in the body and having a third bandgap greater than the second bandgap; and a third solar subcell above said interlayer in the body and lattice mismatched with respect to the second subcell and with a fourth bandgap smaller than the third bandgap; wherein the non-planar support has a plurality of solar cells mounted thereon, attached to the aircraft, the watercraft or the land vehicle. The aircraft, vessel, or land vehicle of claim 1, wherein the aircraft, vessel, or land vehicle is manned or unmanned. The aircraft, watercraft or land vehicle of claim 1, wherein the aircraft is a powered or de-powered aerostat. The aircraft, watercraft or land vehicle of claim 1, wherein the aircraft is a powered or unpowered Aerodyn. The aircraft, watercraft or land vehicle of claim 5, wherein the aerodyne is a fixed wing or a rotor force. The aircraft, watercraft or land vehicle of claim 1, wherein the watercraft is powered or hovering. The aircraft, watercraft or land vehicle of claim 1, wherein the vessel is motorized or non-motorized. The aircraft, watercraft or land vehicle of claim 1, wherein the watercraft is a surface vehicle or a submersible vehicle. The aircraft, watercraft or land vehicle of claim 1, wherein the land vehicle is motorized or non-motorized. A solar cell device according to claim 1, wherein the grading interlayer has a substantially constant bandgap, and a compositionally graded InGaAlAs series of layers is a monotonic changing lattice constant, so the lattice matching of the second subcell is on one side and the third subcell the other side.

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