Back contact structure and selective contact region buried solar cell comprising the same

A back contact structure of a solar cell, the back contact structure comprising:

• a silicon substrate, the silicon substrate comprising a back surface comprising a plurality of recesses disposed at intervals and a plurality of interval portions between every two of the plurality of recesses, each of the plurality of interval portions comprising two side portions and a middle portion, the two side portions being respectively adjacent to two of the plurality of recesses adjacent to the each of the plurality of interval portions, and the middle portion being disposed between the two side portions;
• a first dielectric layer disposed on the back surface of the silicon substrate;
• a plurality of first doped regions disposed on the first dielectric layer and disposed inside the plurality of recesses, wherein:
• a depth of each of the plurality of recesses is greater than a sum of a thickness of the first dielectric layer and a thickness of each of the plurality of first doped regions that are disposed inside the each of the plurality of recesses;
• and
• the plurality of first doped regions is entirely enclosed inside the plurality of recesses, respectively;
• a plurality of second doped regions each comprising a bottom surface and a top surface opposite the bottom surface, wherein the plurality of second doped regions is disposed on the first dielectric layer, thereby the bottom surface of each of the plurality of second doped regions is directly connected to the first dielectric layer;
• and the plurality of second doped regions is disposed outside the plurality of recesses, and the plurality of second doped regions is enclosed only on the middle portion, thereby the plurality of second doped regions is spatially separated from the plurality of first doped regions disposed inside the plurality of recesses;
• a second dielectric layer disposed between each of the plurality of first doped regions and an adjacent one of the plurality of second doped regions and disposed on the plurality of second doped regions, thereby the second dielectric layer covers at least a portion of the top surface of each of the plurality of second doped regions;
• wherein:
• the first dielectric layer and the second dielectric layer are distinct;
• the second dielectric layer comprises at least one sub-layer;
• and
• the second dielectric layer covers side walls of each of the plurality of recesses;
• and
• a conductive layer directly disposed on the plurality of first doped regions and the plurality of second doped regions.