Photovoltaic Panel and Cell with Fine Fingers and Method of Manufacture of the Same
A photovoltaic cell has a photosensitive substrate and a plurality of fingers in ohmic contact with the substrate. At least one of the fingers has an average width of less than about 95 microns. The cell also has a plurality of busbars in ohmic contact with the fingers. At least two of the busbars that are spaced less than about 38 millimeters apart intersect the at least one finger (i.e., the finger(s) having an average width of less than about 95 microns).
1 . A photovoltaic cell comprising:
a photosensitive substrate;
a plurality of fingers in ohmic contact with the substrate, at least one of the fingers having an average width of less than about 95 microns;
a plurality of busbars in ohmic contact with the fingers,
at least two of the busbars intersecting the at least one of the fingers, the at least two busbars being spaced less than about 38 millimeters apart.
2 . The photovoltaic cell as defined by claim 1 wherein the at least two busbars are spaced no less than about six millimeters apart.
3 . The photovoltaic cell as defined by claim 1 wherein no busbar on the substrate is spaced more than about 38 millimeters from another adjacent busbar.
4 . The photovoltaic cell as defined by claim 1 wherein the plurality of busbars are generally equally spaced apart a given distance, the given distance being no more than about 15 millimeters.
5 . The photovoltaic cell as defined by claim 1 wherein the substrate comprises a sheet wafer formed from doped polysilicon.
6 . The photovoltaic cell as defined by claim 5 wherein the substrate comprises a string ribbon wafer.
7 . The photovoltaic cell as defined by claim 1 wherein each of the plurality of intersected fingers has an average height of no greater than about twenty microns, and an average width of no greater than about sixty microns.
8 . The photovoltaic cell as defined by claim 1 further comprising a plurality of tabs in ohmic contact with the plurality of busbars, the plurality of tabs having a generally planar surface that forms an acute angle with the substrate.
9 . The photovoltaic cell as defined by claim 1 wherein at least one of the busbars is discontinuous and comprises a plurality of spaced pads.
10 . The photovoltaic cell as defined by claim 1 wherein at least one of the fingers has a repeating discontinuity.
11 . The photovoltaic cell as defined by claim 1 wherein each busbar and each finger comprises a screen printed conductive material.
12 . The photovoltaic cell as defined by claim 1 wherein each of the plurality of fingers has an average width of no greater than about 65 microns.
13 . The photovoltaic cell as defined by claim 1 wherein the substrate has a bottom face, the photovoltaic cell further comprising:
a conductive sheet secured to the bottom face of the substrate; and
a tab between the conductive sheet and the bottom face of the substrate.
14 . The photovoltaic cell as defined by claim 1 wherein the substrate has an average thickness that is no greater than about 300 microns.
15 . The photovoltaic cell as defined by claim 1 further comprising a plurality of tabs connected with the busbars, the substrate having a top surface containing the fingers and busbars, the fingers, tabs and busbars together covering no more than about six percent of the top surface of the substrate.
16 . The photovoltaic cell as defined by claim 1 wherein the at least one finger has an average width of no less than about 35 microns.
17 . The photovoltaic cell as defined by claim 1 wherein the plurality of fingers comprise only a single layer of conductive material.
18 . A method of fabricating a photovoltaic cell, the method comprising:
providing a photosensitive substrate having a top face;
depositing a plurality of fingers onto the top face of the substrate and into ohmic contact with the substrate, the plurality of fingers each having an average width of less than about 95 microns; and
depositing a plurality of busbars on the top face of the substrate to intersect the plurality of fingers, the plurality of busbars having an outer dimension of greater than about 95 microns, at least two of the plurality of busbars being deposited on the top face of the substrate so that they are separated by no more than about 38 millimeters.
19 . The method as defined by claim 18 wherein depositing a plurality of fingers comprises depositing no more than one layer of conductive material onto the substrate to form the fingers.
20 . The method as defined by claim 19 further comprising electrically connecting a tab to at least one of the one layer fingers.
21 . The method as defined by claim 19 wherein the conductive material comprises a silver based material.
22 . The method as defined by claim 18 wherein depositing a plurality of fingers comprises screen printing the fingers onto the top face of the substrate.
23 . The method as defined by claim 18 wherein the plurality of busbars are spaced no less than about six millimeters apart.
24 . The method as defined by claim 18 wherein no busbar on the substrate is spaced more than about 38 millimeters from another adjacent busbar.
25 . The method as defined by claim 18 wherein providing comprises providing a string ribbon wafer formed from polysilicon.
26 . The method as defined by claim 18 wherein depositing a plurality of fingers comprises depositing a substantially continuous line of conductive material across the front face of the substrate to form a single, substantially continuous finger.
27 . The method as defined by claim 26 wherein the single, substantially continuous finger has an irregular break formed after depositing the plurality of fingers.
28 . The method as defined by claim 18 wherein depositing a plurality of fingers comprises depositing a line of conductive material to have a regularly spaced discontinuity.
29 . The method as defined by claim 18 wherein depositing a plurality of busbars comprises depositing fifteen busbars on the top face of the substrate.
30 . The method as defined by claim 18 wherein depositing a plurality of busbars comprises depositing a plurality of spaced pads on the top face of the substrate.
31 . The method as defined by claim 18 further comprising electrically connecting a plurality of tabs to the plurality of busbars.
32 . The method as defined by claim 31 wherein each one of the plurality of tabs has a generally planar surface that forms an acute angle with the substrate when electrically connected.
33 . The method as defined by claim 18 wherein the substrate has a bottom face, the method further comprising:
securing a conductive sheet to the bottom face of the substrate; and
securing a tab between the conductive sheet and the bottom face of the substrate.
34 . The method as defined by claim 18 wherein depositing a plurality of fingers comprising depositing the plurality of fingers to have an average width of no less than about 35 microns.
35 . A photovoltaic cell comprising:
a photosensitive substrate;
a plurality of current collecting means in ohmic contact with the substrate, at least one of the collecting means having an average width of less than about 95 microns;
a plurality of tab connection means in ohmic contact with the fingers,
at least two of the tab connection means intersecting a plurality of the fingers, the at least two tab connection means being spaced less than about 38 millimeters apart.
36 . The photovoltaic cell as defined by claim 35 wherein the at least two tab connection means are spaced no less than about six millimeters apart.
37 . The photovoltaic cell as defined by claim 35 wherein no tab connection means on the substrate is spaced more than about 38 millimeters from another adjacent tab connection means.
38 . A photovoltaic cell comprising:
a photosensitive substrate;
a plurality of spaced pads in ohmic contact with the substrate, the plurality of pads forming a plurality of discontinuous busbars, each of the plurality of pads having an outer dimension that is greater than 100 microns,
each pad in a set of the plurality of pads having a contiguous finger portion extending therefrom, each contiguous finger portion having an average width of no greater than about 95 microns.
39 . The photovoltaic cell as defined by claim 38 wherein the finger portions form a discontinuous finger comprising a repeating discontinuity.
40 . The photovoltaic cell as defined by claim 38 wherein a first finger portion of a first pad has a first end, a second finger portion of a second pad having a second end, the first end being spaced no more than about two electron diffusion lengths from the second end.
41 . The photovoltaic cell as defined by claim 38 further comprising a plurality of tabs secured to the plurality of pads.
42 . The photovoltaic cell as defined by claim 38 wherein at least two of the busbars are spaced less than about 38 millimeters apart.
43 . The photovoltaic cell as defined by claim 38 wherein the finger portions of the set of the pads form a single continuous finger.
44 . The photovoltaic cell as defined by claim 43 wherein the single continuous finger has at least one irregularly repeating discontinuity.
45 . The photovoltaic cell as defined by claim 38 wherein each pad and each finger portion comprises a screen printed conductive material.
46 . The photovoltaic cell as defined by claim 38 wherein the substrate comprises a string ribbon crystal wafer.
47 . The photovoltaic cell as defined by claim 38 wherein the finger portions have only a single layer of conductive material.
48 . The photovoltaic cell as defined by claim 38 wherein each of the plurality of finger portions has an average height of no greater than about twenty microns, and an average width of no greater than about sixty microns.
49 . The photovoltaic cell as defined by claim 38 further comprising a plurality of tabs in ohmic contact with the plurality of busbars, the plurality of tabs having a generally planar surface that forms an acute angle with the substrate.
50 . The photovoltaic cell as defined by claim 38 wherein each of the finger portions has an average width of less than about 65 microns.
51 . The photovoltaic cell as defined by claim 38 wherein the substrate has a bottom face, the photovoltaic cell further comprising:
a conductive sheet secured to the bottom face of the substrate; and
a tab between the conductive sheet and the bottom face of the substrate.
52 . A photovoltaic panel comprising:
a plurality of electrically connected photovoltaic cells,
at least one of the photovoltaic cells comprising:
a photosensitive substrate;
a plurality of fingers in ohmic contact with the substrate, at least one of the fingers having an average width of less than about 95 microns; and
a plurality of busbars in ohmic contact with the fingers,
at least two of the busbars intersecting a plurality of the fingers, the at least two busbars being spaced less than about 38 millimeters apart.
53 . The photovoltaic cell as defined by claim 52 wherein the at least two busbars are spaced no less than about six millimeters apart.
54 . The photovoltaic cell as defined by claim 52 wherein no busbar on the substrate is spaced more than about 38 millimeters from another adjacent busbar.