This application relates to the photovoltaic field. Embodiments of this application provide a back-contact battery, a back-contact tandem battery, and a photovoltaic module. The back-contact battery's grid includes a first grid and a second grid. The first grid is connected to an edge grid line, and the second grid is spaced apart from the edge grid line. The second grid includes at least a first sub-grid, a second sub-grid, and a third sub-grid. Along a second direction, the length of the second sub-grid is greater than the length of the first sub-grid and less than the length of the third sub-grid. The vertical distances L1 between the first sub-grid and the chamfered edge, L2 between the second sub-grid and the chamfered edge, and L3 between the third sub-grid and the second edge are all 0.8mm to 1.2mm. The chamfered edge can disperse stress in the
edge region of the battery, improve the battery's
mechanical strength, and reduce defect areas. The chamfered
edge structure combined with the arrangement of the second grid improves the electrical reliability of the
edge region of the back-contact battery, thereby enhancing the
photoelectric conversion efficiency of the back-contact battery.