A solar cell unit, comprising: a cell including a cell substrate and a secondary grid line disposed on a front surface of the cell substrate ; and a conductive wire intersected and welded with the secondary grid line , the secondary grid line having a width in a welding position with the conductive wire greater than a width thereof in a non-welding position, wherein the secondary grid line preferably has a width in the welding position greater than or equal to a diameter or width of the conductive wire ; characterized in that a binding force between the conductive wire and the cell ranges from 0.2 N to 0.6 N, wherein the secondary grid line has a width of 0.08-0.24 mm in the welding position, and a width of 0.015-0.03mm in the non-welding position; the width of the secondary grid line is a maximum size in a direction orthogonal to a longitudinal direction of the secondary grid line , and/or wherein the secondary grid line has a height of 0.01-0.03 mm in the welding position, and a height of 0.005-0.01 mm in the non-welding position, wherein the binding force is tested by placing the cell horizontally at a testing position of a tensile tester, by disposing pressing blocks at two sides of the conductive wire; by clamping the conductive wire at a pull ring of a tension meter that forms an angle of 45° with the cell; and by actuating the tension meter, such that the tension meter moves uniformly along a vertical direction, pulls up the conductive wire from the surface of the cell and records the pull data tested, in which the data is averaged to obtain the pull data of the conductive wire. a cell including a cell substrate and a secondary grid line disposed on a front surface of the cell substrate ; and a conductive wire intersected and welded with the secondary grid line , the secondary grid line having a width in a welding position with the conductive wire greater than a width thereof in a non-welding position, wherein the secondary grid line preferably has a width in the welding position greater than or equal to a diameter or width of the conductive wire ; characterized in that a binding force between the conductive wire and the cell ranges from 0.2 N to 0.6 N, wherein the secondary grid line has a width of 0.08-0.24 mm in the welding position, and a width of 0.015-0.03mm in the non-welding position; the width of the secondary grid line is a maximum size in a direction orthogonal to a longitudinal direction of the secondary grid line , and/or wherein the secondary grid line has a height of 0.01-0.03 mm in the welding position, and a height of 0.005-0.01 mm in the non-welding position, wherein the binding force is tested by placing the cell horizontally at a testing position of a tensile tester, by disposing pressing blocks at two sides of the conductive wire; by clamping the conductive wire at a pull ring of a tension meter that forms an angle of 45° with the cell; and by actuating the tension meter, such that the tension meter moves uniformly along a vertical direction, pulls up the conductive wire from the surface of the cell and records the pull data tested, in which the data is averaged to obtain the pull data of the conductive wire. <EOS>