This disclosure generally relates to photovoltaic (PV) cells and methods of manufacturing PV cells and, more specifically, to crystalline PV cells with electrodes and methods of manufacturing the same.
Photovoltaic (PV) modules are devices which convert solar energy into electricity. A PV module typically includes several PV cells (connected in series and/or in parallel) that generate electricity in response to sunlight incident on the surface of the cells.
To extract energy from the PV cells, electrodes are manufactured on one or both faces of a crystalline silicon wafer. Various techniques are known for manufacturing PV cell electrodes. In one known method, electrodes include fingers and bus bars are screen printed onto a surface of the silicon wafer using silver (Ag) paste. Some other PV cells are manufactured by screen printing fingers from silver and soldering separate bus bars to fingers. In still another technique, fingers are screen printed on the silicon wafer using silver. A copper (Cu) mesh electrode is positioned over the screen printed fingers. The mesh electrode includes thin (relative to bus bars) copper fingers that extend parallel to each other and intercept the silver screen printed fingers. The copper fingers are electrically coupled to the screen printed fingers and serve the same purpose as bus bars. Some of the known techniques are electrically inefficient (e.g., exhibit unacceptably high ohmic losses), manpower inefficient, use costly material (e.g. silver), and/or are otherwise relatively costly.
This Background section is intended to introduce the reader to various aspects of art that may be related to various aspects of the present disclosure, which are described and/or claimed below. This discussion is believed to be helpful in providing the reader with background information to facilitate a better understanding of the various aspects of the present disclosure. Accordingly, it should be understood that these statements are to be read in this light, and not as admissions of prior art.
One aspect of the present disclosure is a method of manufacturing a photovoltaic (PV) cell. The method includes depositing a plurality of first fingers on a crystalline silicon wafer. The first fingers extend in a first direction parallel to each other and comprise a substantially non-silver conductive material.
Another aspect of the present disclosure is photovoltaic (PV) cell. The PV cell includes a crystalline silicon substrate, and a plurality of first fingers disposed on the crystalline silicon wafer. The first fingers extend in a first direction parallel to each other and comprise a substantially non-silver conductive material.
Various refinements exist of the features noted in relation to the above-mentioned aspects. Further features may also be incorporated in the above-mentioned aspects as well. These refinements and additional features may exist individually or in any combination. For instance, various features discussed below in relation to any of the illustrated embodiments may be incorporated into any of the above-described aspects, alone or in any combination.
Like reference symbols in the various drawings indicate like elements.
The embodiments described herein generally relate to photovoltaic (PV) cells and methods of manufacturing PV cells. More specifically, embodiments described herein relate to crystalline PV cells with non-silver electrodes and methods of manufacturing the same
Referring initially to
Solar panel 102 includes a top surface 106 and a bottom surface 108 (shown in
As shown in
As shown in
At least one layer 118 of solar panel 102 includes photovoltaic (PV) cells. PV cells are constructed from crystalline silicon wafers.
During the manufacture of PV cells 302, electrodes are manufactured on silicon wafer 300 in the areas that will form PV cell 302. In this embodiment, the electrodes include first fingers 400 manufactured on wafer 300 and second fingers 402 applied to wafer 300 and coupled to the first fingers 400.
In this embodiment, first fingers 400 are applied to wafer 300 by screen printing. Screen printing is well known to those skilled in the art and will not be described in detail. In general, a copper paste is applied to wafer 300 through a mask (not shown) that allows the paste to pass to the wafer only in the locations desired for forming the first fingers 400. Wafer 400 is then heated to remove solvents and binders used in the paste, leaving behind the copper first fingers 400. In other embodiments, any other suitable method for forming first fingers 400 may be used. For example, in some embodiments first fingers 400 are formed on PV cell 302 using electroless plating and/or electrochemical plating techniques. In still other embodiments, plasma vapor deposition (PVD), by sputtering or evaporation, may be used to manufacture first fingers 400 on wafer 300.
Rather than using two or three discrete bus bars to couple to first fingers 400, a greater number of smaller, more closely spaced second fingers 402 are coupled to wafer 300 to carry current from first fingers 400. Any suitable number of second fingers 400 may be used. In some embodiments PV cell 302 includes four or more second fingers 400.
One exemplary type of second fingers 402 is shown in
In the illustrated embodiment, copper mesh 600 includes nine of the second fingers 402. In other embodiments, mesh 600 may include more or fewer second fingers 402. In some embodiments, mesh 600 includes more than four second fingers 402. In contrast, a similar PV cell constructed using discrete bus bars attached to first fingers 400 commonly includes only two or three discrete bus bars. Such bus bars are spaced significantly farther apart than second fingers 402 and are significantly wider than second fingers 402. In some known 156 millimeter (mm) PV cells, bus bars are spaced about 78 mm or 52 mm apart. In contrast, second fingers 402 are spaced as close as 8 mm apart. Thus, the effective length of first fingers 400 is reduced in the exemplary PV cell 302 to about 8 mm as compared to 52 mm or 78 mm in some known PV cells.
In other embodiments, mesh 600 is not used and second fingers 402 are formed using several (e.g., four or more) thin, electrically conductive wires. The wires are disposed on wafer 300 in a similar arrangement to second fingers 402 shown in
The PV cells and methods described achieve superior results to some known methods. The PV cells may be manufactured more easily and efficiently than these known methods. Moreover, the material cost of the PV cells may be reduced by, for example, the use of copper and other inexpensive metals for fabrication of the fingers of the PV cell rather than the commonly used, and more expensive, silver.
When introducing elements of the present invention or the embodiment(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.
As various changes could be made in the above without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
This application claims priority to U.S. Provisional Application No. 61/737,589 filed Dec. 14, 2012, the entire disclosure of which is hereby incorporated by reference in its entirety.
Number | Date | Country | |
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61737589 | Dec 2012 | US |