Forming front metal contact on solar cell with enhanced resistance to stress
View Patent ↗System and method of providing a photovoltaic (PV) cell having a cushion layer to alleviate stress impact between a front metal contact and a thin film PV layer. A cushion layer is disposed between an extraction electrode and a photovoltaic (PV) surface. The cushion layer is made of a nonconductive material and has a plurality of vias filled with a conductive material to provide electrical continuity between the bus bar and the PV layer. The cushion layer may be made of a flexible material preferably with rigidity that matches the substrate. Thus, the cushion layer can effectively protect the PV layer from physical damage due to tactile contact with the front metal contact.
1. A photovoltaic assembly comprising:
a photovoltaic cell configured to convert light energy to electrical energy, wherein said photovoltaic cell comprises:
a front metal layer comprising a bus bar on a side along a length of said photovoltaic cell and multiple finger electrodes oriented perpendicular to and extending from said bus bar with one end connected to said bus bar,
a photovoltaic layer disposed under said front metal layer, said front metal layer being disposed closer than said photovoltaic layer to a side of said photovoltaic cell intended to face light, and
a substrate layer disposed under said photovoltaic layer;
a front contact disposed above of said front metal layer and thereby above said bus bar and above the end of each of said finger electrodes connected to said bus bar, and said front contact configured to conduct electrical current originated from the photovoltaic cell to external circuitry;
a cushion layer disposed between said front contact and said front metal layer thereby closer to said side of said photovoltaic cell intended to face light than said front metal layer, wherein said cushion layer includes a nonconductive material that is less rigid than said front contact and comprises a plurality of vias filled with a conductive material, wherein each filled via is aligned with and in direct contact with one finger electrode at the end of that finger electrode that is connected with said bus bar to conduct electrical current between said front contact and said photovoltaic layer via said front metal layer, and wherein an excess portion of said front contact and said cushion layer along said length of said photovoltaic cell wraps over an edge of said photovoltaic cell; and
a back metal layer disposed between said photovoltaic layer and said substrate layer, said back metal layer being configured to interconnect said photovoltaic layer with another photovoltaic layer of a different photovoltaic cell in said photovoltaic assembly,
wherein said nonconductive material of said cushion layer includes a flexible polymer material and said substrate layer includes the flexible polymer material.
2. The photovoltaic assembly as described in claim 1 , wherein a rigidity of said cushion layer matches a rigidity of said substrate layer, and wherein said cushion layer is used to protect said photovoltaic cell from physical damage caused by tactile contact with said front contact.
3. The photovoltaic assembly as described in claim 1 , wherein said flexible polymer material comprises polyethylene terephthalate (PET) combined with pressure sensitive adhesive (PSA).
4. The photovoltaic assembly as described in claim 1 , wherein said photovoltaic layer is less than 10 μm in thickness and comprises a GaAs layer.
5. The photovoltaic assembly as described in claim 1 , wherein said front contact comprises Cu and has a thickness of less than 50 μm.
6. The photovoltaic assembly as described in claim 1 , wherein said front metal layer corresponds to an extraction electrode in said photovoltaic cell.