A solar cell, a cell assembly, and a photovoltaic system are provided. In the solar cell, P-type doped layers and N-type doped layers are disposed on a first surface of a silicon wafer, and a thickness of a passivation film layer on at least some regions of the N-type doped layers is greater than a thickness of at least some regions of the passivation film layer on the P-type doped layers. By performing cooperative optimization design of different thicknesses on the passivation film layer on at least some regions of the N-type doped layers and at least some regions of the P-type doped layers, and setting the thickness of the passivation film layer on at least some regions of the N-type doped layers to be greater, the passivation effects of different doped regions of the solar cell can achieve a better matching effect.