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 such that a protrusion is formed between two adjacent recesses of the plurality of recesses;
• a plurality of first conductive regions and a plurality of second conductive regions disposed alternately in the plurality of recesses, wherein each first conductive region comprises a first dielectric layer and a first doped region which are disposed successively in the plurality of recesses, and each second conductive region consists of a second doped region;
• a second dielectric layer, wherein the second dielectric layer is at least one in number;
• and
• a conductive layer disposed on the plurality of first conductive regions and the plurality of second conductive regions;
• wherein
• a thickness of the plurality of first conductive regions is less than a depth of the plurality of recesses, and the first dielectric layer and the first doped region are enclosed inside the plurality of recesses;
• the second dielectric layer comprises a first portion, a second portion, and a third portion;
• the first portion is disposed on and covers a top surface of the first doped region, and the first portion is constrained on the plurality of recesses where the plurality of first conductive regions is disposed;
• the second portion is disposed on and covers a side wall of the plurality of recesses where the plurality of second conductive regions is disposed and a top surface of the second conductive region, and the second portion is constrained inside the plurality of recesses where the plurality of second conductive regions is disposed;
• and
• the third portion is disposed between the first portion and the second portion and is constrained on the protrusion.