Thin-film solar module

Details Thin-film solar module Thin-film solar module

1999-10-19

2001-08-14

Diamond, Alan (Department: 1753)

Batteries: thermoelectric and photoelectric

Photoelectric

Panel or array

C136S244000, C136S256000, C136S257000, C257S443000, C257S448000, C257S431000, C257S435000

Reexamination Certificate

active

06274804

ABSTRACT:

FIELD OF THE INVENTION
This invention relates to a thin-film solar module.
BACKGROUND OF THE INVENTION
A solar module known from DE 198 03 326/U.S. Pat. No. 6,013,870 contains a number of solar cells tandem mounted and series-connected on a common substrate. The module also includes a number of adjacent diodes, also referred to as bypass diodes, likewise tandem mounted and connected in series but antiparallel to the solar cells on the same substrate. The structure consists for example of a glass wafer as the substrate , the front electrode layer deposited thereon, the photovoltaically active layer sequence located thereon, and the subsequently applied back electrodes (See FIG. 3 of DE 198 03 326/U.S. Pat. No. 6,013,870). The substrate and front electrode layer are transparently designed so that sunlight can penetrate into the photovoltaically active layers through said structure in order to produce the necessary mobile electric charge carriers. This is known as a superstrate structure.
The solar module can also be constructed as follows. On the substrate (e.g. a glass wafer) the back electrode layer is first deposited, then the photovoltaically active layer sequence , and subsequently the front electrode layer. In this case sunlight penetrates into the photovoltaically active layers through the last-named layer, which is now transparently designed. This module structure is called a substrate structure
In a module according to DE 198 03 326/U.S. Pat. No. 6,013,870, an electric connection is present between a bypass diode and adjacent solar cell by reason of an electric conductivity (transverse conductivity) of the photovoltaically active layer sequence. Then the front and back electrode layers of the diode and its adjacent solar cell are interconnected by a direct electric contact. Consequently, the electric power of the solar module is reduced. This effect can occur because the photovoltaically active layer is not separated in the area of the separation of the front or back electrode layer in the grooves and of this module.
In the above-described module, the bypass diodes are also not covered upon incidence of light on the side facing the light and thus reduce the power of the solar cell by reason of their opposite polarity to the cell. The produced photocurrent of the solar cell is reduced by the amount of the photocurrent of the bypass diode.
SUMMARY OF THE INVENTION
The invention provides a solar module which can be produced using integrated thin-film technology, has a diode connected in the reverse direction for each individual solar cell (see DE 198 03 326/U.S. Pat. No. 6,013,870). The solar module avoids power losses caused by the transverse conductivity between the diode and the adjacent cell due to the photoactive layer sequence. A further object of the invention is that it prevents power loss of the solar module arising from the illuminated bypass diodes by an opaque mask of the bypass diodes. This is accomplished by means of a lacquering or screen print on the front glass wafer.
It is accordingly first provided that the front and back electrode layers of adjacent diodes are not electrically contacted directly with each other. This eliminates the direct series connection of the diodes. Further, overlap zones are formed by a projecting edge area of an electrode layer of a solar cell or diode engaging a recess of the corresponding electrode layer of the adjacent diode or solar cell and thus overlapping the superjacent or subjacent zone of the other electrode layer of said adjacent diode or solar cell. Finally, each diode is connected in the reverse direction with the adjacent solar cell in at least two overlap zones. Specifically, the front electrode layer of the particular diode is electrically contacted with the back electrode layer of the particular solar cell in at least one of said overlap zones. Also, the back electrode layer of said diode is electrically contacted with the front electrode layer of said solar cell in at least one other of said overlap zones.
The abovementioned overlap zones can be produced in simple, time-saving and cost-effective fashion in the course of the integrated industrial process by corresponding structuring of the particular electrode layers, as will become clearer below with reference to the embodiments. The contacting in the overlap areas also ensures firstly that each individual solar cell has assigned thereto a diode connected in the reverse direction thereto. Secondly, it causes the diodes to be series-connected altogether but in the reverse direction to the solar cells. While the series connection of the solar cells is effected directly in the usual way, i.e. by contacting the front electrode layer of a solar cell with the back electrode layer of the adjacent cell, the series connection of the diodes is effected by indirect means via the overlap zones and the electrode layers of the assigned solar cells.
To prevent each diode from being electrically short-circuited with its adjacent solar cell by a shunt resistance, represented by the transverse conductivity of the photovoltaically active layer sequence, the photovoltaically active layer sequence is removed between diode and solar cell.


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Patent Abstracts of Japan, abstract for JP 02-298080, dated Dec. 10, 1990 (1 page).

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