Solar cell

A solar cell, comprising:

• a substrate;
• an emitter, a first passivation film, an antireflection film and a first electrode that are disposed on an upper surface of the substrate;
• a tunneling layer, a retardation layer, a field passivation layer, a second passivation film and a second electrode that are disposed on a lower surface of the substrate;
• wherein the retardation layer is configured to retard migration of doped ions from the field passivation layer to the substrate, and the retardation layer includes:
• a first retardation sub-layer aligned with a projection of the second electrode, and
• a second retardation sub-layer misaligned with a projection of the second electrode, wherein at least the second retardation sub-layer is configured as an intrinsic semiconductor layer, and a material of the intrinsic semiconductor layer is the same as a material of the field passivation layer;
• wherein a retardation capability of the second retardation sub-layer is weaker than a retardation capability of the first retardation sub-layer;
• a retardation capability of a particular retardation sub-layer is related to a longest distance that a doped ion that undergoes thermal diffusion is able to migrate from the field passivation layer towards the substrate through the particular retardation sub-layer;
• and the shorter the longest distance that the doped ion undergoing thermal diffusion migrates, the stronger the retardation capability of the retardation layer;
• wherein the first retardation sub-layer includes at least two film layers, the at least two film layers includes a first surface layer toward the tunneling layer and a second surface layer toward the field passivation layer;
• a material of the first surface layer is a metal, and a material of the second surface layer is a compound generated from a reaction with the metal.

A method for preparing a solar cell, comprising:

• providing a substrate;
• forming an emitter, a first passivation film, an antireflection film and a first electrode on an upper surface of the substrate;
• forming a tunneling layer, a retardation layer, a field passivation layer, a second passivation film and a second electrode on a lower surface of the substrate;
• wherein the retardation layer is configured to retard a migration of doped ions from the field passivation layer to the substrate, and the retardation layer includes:
• a first retardation sub-layer aligned with a projection of the second electrode, and a second retardation sub-layer misaligned with a projection of the second electrode, wherein at least the second retardation sub-layer is configured as an intrinsic semiconductor layer, and a material of the intrinsic semiconductor layer is the same as a material of the field passivation layer;
• wherein a thickness of the first retardation sub-layer is smaller than a thickness of the second retardation sub-layer in a direction perpendicular to the lower surface of the substrate;
• wherein the first retardation sub-layer includes at least two film layers, the at least two film layers includes a first surface layer toward the tunneling layer and a second surface layer toward the field passivation layer;
• a material of the first surface layer is a metal, and a material of the second surface layer is a compound generated from a reaction with the metal.