Method of Producing Electrical Contacts on a Silicon Solar Cell

This invention relates to a method of producing electrical contacts on a silicon solar cell.

Today contacts are produced on a silicon solar cell usually using layers of metals reheated and vapour deposited under high vacuum. Since the high vacuum deposition process is relatively expensive, it has also been suggested that contacts on solar cells should be provided by spraying on metals with the aid of a plasma-jet technique. The electrical contacts are even applied with the aid of a so-called screen printing method. The common feature of all of these methods is that a part of the material which is to be used for the contacts is lost and the methods are relatively expensive.

It is an object of the present invention to provide a method of producing electrical contacts on solar cells in which the contact material not required for the contacts can be recovered completely. In addition it is cheaper than all the above mentioned known methods.

According to the invention, there is provided a method of producing electrical contacts on a silicon solar cell comprising stamping contact shapes from a carrier carrying a metal film or foil adhered to one side thereof and applying the stamped out metal film or foil to the surface of said silicon to adhere said film or foil to said surface of said silicon while removing said carrier from said film or foil.

Further according to the invention, there is provided a method of producing electrical contacts on a silicon solar cell, wherein a metal film or foil adhering to one side of a carrier is stamped out together with the carrier in the shape of the contacts; and the stamped contact film or foil is applied to the silicon so as to be detached from the carrier and to adhere to the silicon surface.

The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:

FIG. 1a is a schematic side view of a film or foil as a carrier being stamped out in accordance with the invention;

FIG. 1b is a schematic side view of a stamped out carrier with its film or foil;

FIG. 2a shows the carrier with its film or foil being applied to the surface of a silicon solar cell;

FIG. 2b shows the film or foil adhered to the silicon with the carrier removed;

FIG. 3a shows an alternative application of the carrier and foil to the silicon surface;

FIG. 3b shows the removal of the carrier from the foil shown in FIG. 3a, and

FIG. 3c shows the completed adhered contact.

Basically the invention proposes a method of producing electrical contacts on a silicon solar cell, in which a metal film or foil adhering to one side of a carrier is stamped together with the carrier into the shape of the contacts and the stamped contact film or foil is applied to the silicon so that it detaches itself from the carrier and adheres to the silicon surface.

The contact film or foil adhering to the surface of the silicon may then be sintered or alloyed in a suitable atmosphere. Films or foils comprising aluminium, aluminium/silicon alloys, iron/silicon alloys, tin, lead, copper, antimony, arsenic, zinc or alloys of these metals with each other are suitable as contact materials for the silicon solar cells. The stamped out contact film or foil applied to the silicon surface is sintered or alloyed in, preferably in a reducing atmosphere for example, in a continuous furnace. The contact film or foil may also be sintered or alloyed in by means of brief heating with the aid of a focussed light beam or laser. In practice, it is also profitable to press the contact film or foil adhering to the silicon surface against the silicon surface mechanically during the alloying process.

Reference is now had to the drawings which show specific embodiments of the invention. In FIG. 1a a film or foil 1 comprising an aluminium/silicon alloy is stamped out with the aid of a die 3 and a stamp 4. FIG. 1b shows the stamped element comprising the carrier 2 and the film or foil 1.

In FIG. 2a the stamped element comprising the carrier 2 and metal film or foil 1 is placed onto a silicon solar cell with its metal face in contact therewith. In FIG. 2b the carrier 2 is released from the metal film or foil and the metal film or foil 1 adheres to the surface of the solar cell 5.

In an alternative to the method steps shown in FIG. 2, in FIG. 3a the stamped element 2 with the metal film or foil 1 is placed onto the surface of a silicon solar cell 5.

The carrier 2, which can be made of an organic plastic, adheres to the conveyor belt 6 and mechanical pressure 7 is applied between the solar cell 5 and the conveyor belt 6.

In FIG. 3b the conveyor belt 6 is separated from the solar cell 5, the carrier 2 adhering to the conveyor belt 6 while the metal film or foil 1 adheres to the surface of the solar cell 5.

In FIG. 3c, the solar cell 5 together with the metal film or foil 1 has been heated beyond the alloying temperature so that an alloy region 8 has been formed.

It will be understood that the above description of the present invention is susceptible to various modifications changes and adaptations.