Doped region structure and solar cell comprising the same, cell assembly, and photovoltaic system

A cell assembly, comprising:

• a silicon substrate;
• a first doped region and a second doped region, alternately disposed on a back side of the silicon substrate and having opposite polarities;
• a first dielectric layer, disposed on a front side of the silicon substrate;
• a second dielectric layer, wherein an orthogonal projection of at least a portion of the second dielectric layer onto the silicon substrate is disposed between orthogonal projections of the first doped region and the second doped region along a lateral direction of the silicon substrate;
• and
• a first conductive layer and a second conductive layer, respectively disposed in the first doped region and the second doped region;
• wherein:
• each of the first and second doped regions comprises a first doped layer, a passivation layer, and a second doped layer;
• the first doped layer of the first doped region is a part of the silicon substrate;
• the passivation layer of the first doped region is provided on the first doped layer of the first doped region;
• and
• the passivation layer of the first doped region and the passivation layer of the second doped region are of a porous structure, wherein the porous structure comprises a hole region, and at least one of a part of the first doped layer or a part of the second doped layer is disposed in the hole region;
• one of the first doped region and the second doped region is a P-type doped region, and the other of the first doped region and the second doped region is an N-type doped region;
• a hole density of the passivation layer in the P-type doped region is greater than a hole density of the passivation layer in the N-type doped region.