Method of Fabricating a Photovoltaic Module of a Substantially Transparent Construction

1. Field of the Invention

The invention generally relates to a method of fabricating photovoltaic modules, and more particularly to a method of fabricating a photovoltaic module substantially transparent to all energy not used by the cell to produce electricity whereby the overall efficiency of the module is enhanced.

2. Description of the Prior Art

The prior art, of course, is replete with devices and techniques employed in the production of solar cells. Most photovoltaic modules have been designed with a view toward reduction in initial costs of materials. This, of course, results in penalties in performance, of efficiency as well as production costs. However, as pointed out in U.S. application Ser. No. 918,869, now abandoned, it is possible to fabricate a photovoltaic module which is substantially transparent to substantially all solar energy not used to produce electricity. Because of such transparency, the temperature of the module is substantially minimized with an attendant increase in the overall efficiency of the module. For example, it has been found that where cell temperature has been reduced because of module transparency, an improvement in electrical output has been experienced.

Additionally, as can be appreciated by those familiar with the fabrication of photovoltaic modules, it is highly desirable to fabricate photovoltaic or solar modules employing techniques which readily can be adapted for a production-line assembly thereof.

It is, therefore, the general purpose of the instant invention to provide an improved method of fabricating an improved photovoltaic module, said method being adaptable for use in production-line assembly operations.

It is, therefore, an object of the instant invention to provide an improved method of fabricating photovoltaic modules.

Another object is to provide a method of fabricating a photovoltaic module including a plurality of photovoltaic cells substantially transparent to all solar energy not used by the cells in the production of photovoltaic electricity.

These and other objects and advantages are achieved through the practice of a method wherein a plurality of uniformly dimensioned photovoltaic cells are positioned relative to a tool, characterized by a plurality of openings disposed in uniform positional relationship for affording access to the P contact of each of the cells, and thereafter vacuum bonding the cells to a transparent cover plate, as will become more readily apparent by reference to the following description and claims in light of the accompanying drawings.

FIG. 1 is a perspective view of a photovoltaic module fabricated employing the method of the instant invention.

FIG. 2 is a perspective view of a planar tool employed fabricating the module shown in FIG. 1.

FIGS. 3 through 11 are perspective views illustrating sequential steps performed in a method resulting in the photovoltaic module shown in FIG. 1.

FIG. 12 is a fragmented, sectional view of the module shown in FIG. 1.

FIG. 13 is a fragmented top plan view of a portion of the partially completed module shown in FIG. 3, but on an enlarged scale.

FIG. 14 is a fragmented bottom plan view of a portion of the partially completed module shown in FIG. 6, but also on an enlarged scale.

FIG. 15 is a fragmented, cross sectional view of the module in its completed form.

FIG. 16 is a cross sectional view of a vacuum fixture employed in the fabrication of the module.

FIG. 17 is a diagrammatic view illustrating a circuit for the module.

Referring now to the drawings with more particularity, wherein like reference characters designate like or corresponding parts throughout the several views, there is shown in FIG. 1 a photovoltaic module, generally designated 10, fabricated in accordance with a method embodying the principles of the instant invention.

As shown in FIG. 1, the module 10 includes a plurality of individual solar cells 12 of circular configurations and of common diameters. The solar cells 12, as shown, comprise N on P cells having an N surface 14, FIG. 13, and a P surface 16, FIG. 14. To the N surface 14 of each of the cells 12 there is connected N contacts 18, of known design, while to the P surface 16 there is connected P contacts 20, FIG. 14. Since photovoltaic cells are well known, a more detailed description thereof is omitted in the interest of brevity.

In fabricating the module 10, a plurality of solar cells 12 are connected in series. To achieve this, the cells are positioned on the surface of a tool designated 22, FIG. 2. The tool 22 is provided with a plurality of uniformly spaced, circular openings 24 about which there is arranged stop pins 26, of uniform height. The purpose of these pins is to support the solar cells 12 in a registered relationship with the openings 24 and to maintain separation of the cells and adhesive from the cover plate during initial vacuum application, therefore, it will be appreciated that the pins 26 are similarly positioned about each of the openings.

As illustrated in FIG. 3, the solar cells 12 are deposited on the tool 22 in registration with the openings 24, and suitable interconnects 28 are positioned to be soldered to the N contacts 18 as well as to the P contacts 20. The interconnects 28 are now soldered to the N contacts 18 employing a suitable soldering gun 29. The interconnects 28, as best illustrated in FIGS. 13, 14 and 15 are provided to connect the P contact of one cell 12 with the N contact of an adjacent cell 12.

Following the soldering of the interconnect 28 to the N contact, as shown in FIG. 4, the solder is removed through the use of a suitable cleaning gun 30. Subsequent to a removal of debris, such as solder flux and the like, a tool cover 32, FIG. 5, comprising a planar member is positioned over the N contact surfaces of the solar cells 12. The cover 32 serves to hold the cells 12 in place for facilitating an inversion of the cells 12, to an orientation as shown in FIG. 6. With the cover 32 in place, soldering of the interconnects 28 to the P contacts 20 of the cells is initiated employing the gun 29. Of course, once the interconnects 28 have been soldered to the P contacts 20 of the solar cells 12, solder flux is removed therefrom employing the cleaning gun 30. It is to be understood that the opposite surface contacts for the cells 12, at the opposite ends of the thus connected array, are provided with leads, not shown, necessary to establish a series circuit as depicted in FIG. 17.

The tool 22 now is inverted for a second time and thereafter the cover 32 is removed. To the N contact surface for each of the solar cells 12 is applied a glob of clear adhesive 33, as illustrated in FIG. 8. A suitable adhesive applicator A is employed for this purpose. Following the deposit of the adhesive on the N surface of the solar cells 12, a glass cover plate 34 is deposited in contiguous relation with the cells, as the cells are supported on the tool 22, as indicated in FIG. 9. The cover plate 34 preferably comprises a sheet of glass highly pervious to solar radiation. Such is obtainable from the Sunadex Corporation under the designation ASG and comprises a low-iron, high transparent glass sheet.

Next, the cells 12 are vacuum bonded to the cover plate 34. To effect a vacuum bonding of the cells 12 to the cover glass a thin film 36 of substantially impervious material, such as a film of PVC, now is deposited on the surface of the tool 22, opposite the surface on which rests the cells 12, FIGS. 10 and 11, forming an assembly 37. Thereafter, the resulting assembly designated 37 is inserted into a vacuum fixture 38 and supported as shown in FIG. 16. The fixture includes an impervious cover 39 forming vacuum chamber 39' and 39", FIG. 16, adapted to be connected with separate sources of vacuum, not shown.

It should be apparent that the chamber 39' includes an hermetic seal established about the periphery of the assembly 37 whereby a vacuum may, as desired, be established between the assembly 37 and the cover 39. A vacuum now is introduced into the chambers 39' and 39", about the solar cells 12, as they are supported in the fixture 38. Then the diaphragm 36 is subjected to atmospheric pressure by venting chamber 39" while maintaining 39" under vacuum. Atmospheric pressure acting against the diaphragm 36 forces the solar cells 12 into a vacuum bonding engagement with the cover plate 34. The vacuum is held until the adhesive spreads uniformly, whereupon the assembly 37 is removed from the fixture 38 and the diaphragm 36 and tool 22 are now separated.

The cover plate 34 having the solar cells mounted thereon now is placed in a suitable structural frame member 40 and inverted preparatory to receiving on the surface of the solar cells 12 a layer 42 of transparent adhesive. The layer 42 is now permitted to cure. Upon completion of the curing process of the layer 42 of adhesive, the module 10 is ready for operation simply by making necessary circuit connections employing the leads aforementioned, but not shown.

In view of the foregoing, it should readily be apparent that the method which embodies the principles of the instant invention provides a practical and economic method readily adaptable to assembly line production techniques, whereby automation of fabrication of transparent photovoltaic modules is faciliated.