BACKGROUND OF THE INVENTION

In a typical conventional PV module, the PV cells are electrically connected in serial or parallel via conductive ribbons to form a PV string array. The common method of connecting these PV cells is through soldering process, referred to as tabbing and stringing. Once a PV string array is formed, the ribbons of individual PV strings are connected together by a module busbar to establish a circuit, thus completing the PV module electrical circuitry.

Where as in the case of a shingled PV module, one PV cell is partially overlapped onto another PV cell. During shingling process, the rear busbar contact area of a PV cell comes into contact with the front busbar contact area of another PV cell. This step can be repeated multiple times to form a PV string which are connected to each other to establish an electrical connection.

The cell overlapping process can be made possible by directly overlapping the busbars of the PV cells on top of each other to establish electrical connection, but the downside of this method is that these cells are susceptible to misalignment during the assembly process or post assembly process. When the position of these PV cells are not secured properly, any influence of external force, whether it is caused by equipment vibration, vacuum pick-up process or even finished product reliability testing phase, can greatly influence the positioning of the PV cells assembly. In some instances, intermediary conductive materials with adhesion properties are introduced between the busbars to provide a more reliable connection, both mechanically and electrically, but with the introduction of these materials, the risk of electrical shorting, which leads to catastrophic field failures is more eminent. The intermediary conductive materials which are introduced between the busbars tends to squeeze out of the overlapping region as a result of compression between two flat busbar surfaces during shingling process. This leads to PV cell shunting, hotspot failures and other reliability issues. These intermediary conductive materials are normally manufactured with conductive particles and filler materials. To ensure the electrical resistance is kept low, the typical choice for conductive particles is silver. With these materials being added into the PV module manufacturing process, the downside of this is cost is increased significantly.

SUMMARY OF THE INVENTION

Embodiments of the present disclosure generally relate to the method of interconnecting shingled PV cells. More particularly, embodiments of the subject matter relate to techniques for interconnecting shingled PV cells in a reliable manner, without the introduction of any intermediary conductive materials which include, but not limited to: 1) Solder paste; 2) Electrically Conductive Adhesive (ECA); 3) Solder ribbons. The present invention discloses a method to interconnect PV cells in a shingled manner with the introduction of non-conductive bonding material, whereby the non-conductive bonding material is applied around the overlapping region of the PV cells. The PV cells assembly is then cured using various curing techniques until the bonding material is cured. Once the bonding material is cured, the PV cells which are interconnected to form into a PV string are now electrically interconnected and its position is secured firmly by the bonding material. Moreover, the bonding material used in the present invention is electrically non-conductive in nature. This eliminates the risk of electrical shorting completely, even when there is excessive material squeeze out. As an added advantage, the cost for non-conductive materials are significantly lower than electrically conductive materials.

According to a first aspect of the invention, a method of interconnecting two shingled PV cells is provided, comprising: Step 1: placing a PV cell on a flat surface; Step 2: applying non-conductive bonding material on the surface of the PV cell; Step 3: placing another PV cell in a partial overlapping manner, such that the busbars of both PV cells comes into contact with each other; and Step 4: curing the PV cells assembly. The variation in curing methods used in this invention includes; 1) Heat curing technique; 2) Ultraviolet (UV) exposure curing technique; 3) Contact and non-contact force application technique.

According to a second aspect of the invention, a method of interconnecting two shingled PV cells is provided, comprising: Step 1: placing a PV cell on a flat surface; Step 2: placing another PV cell in a partial overlapping manner, such that the busbars of both PV cells comes into contact with each other; Step 3: applying non-conductive bonding material on the edge of the PV cell; and Step 4: curing the PV cells assembly. The variation in curing methods used in this invention includes; 1) Heat curing technique; 2) Ultraviolet (UV) exposure curing technique; 3) Contact and non-contact force application technique.

According to a third aspect of the invention, a method of interconnecting two shingled PV cells is provided, comprising: Step 1: placing a PV cell on a flat surface; Step 2: applying non-conductive bonding material on the surface of the PV cell; Step 3: placing another PV cell in a partial overlapping manner, such that the busbars of both PV cells comes into contact with each other; Step 4: applying non-conductive bonding material on the edge of the PV cell; and Step 5: curing the PV cells assembly. The variation in curing methods used in this invention includes; 1) Heat curing technique; 2) Ultraviolet (UV) exposure curing technique; 3) Contact and non-contact force application technique.

This method of interconnection includes, but not limited to: 1) to establish connection between PV cells; 2) to establish connection between shingled PV strings; 3) to establish connection between PV cell and other components; 4) to establish connection to external circuitry, within a shingled PV module.

This interconnection method can be used to establish series, parallel and a combination of series and parallel circuit design construction.

The bonding material type and application volume is selected to provide reliable mechanical strength without jeopardizing the electrical connections. The bonding material is electrically non-conductive. The bonding material includes, but not limited to: 1) Epoxy based; 2) Gel based; 3) Tape based. The region of application includes, but not limited to: 1) Front side of PV cell; 2) Rear side of PV cell; 3) Edges of PV cell.

