Trench process and structure for backside contact solar cells with polysilicon doped regions

A solar cell comprising:

• a substrate having a front side and a backside;
• a thin dielectric layer disposed on the backside of the substrate;
• a P-type doped polysilicon region that is disposed on the thin dielectric layer;
• an N-type doped polysilicon region that is adjacent to the P-type doped polysilicon region and disposed on the thin dielectric layer;
• an isolation region that is disposed between and separates perimeters of the N-type doped polysilicon region and the P-type doped polysilicon region;
• a first metal contact finger that contacts the P-type doped polysilicon region;
• and
• a second metal contact finger that contacts the N-type doped polysilicon region.

A method of fabricating a solar cell, the method comprising:

• forming a first dielectric layer on a substrate;
• forming an undoped polysilicon layer on the first dielectric layer;
• doping the undoped polysilicon layer into a P-type doped polysilicon region and an N-type doped polysilicon region, wherein the N-type doped polysilicon region is adjacent to the P-type doped polysilicon region;
• and
• forming an isolation region that separates perimeters of the P-type doped polysilicon region and the N-type doped polysilicon region.

A method of fabricating a solar cell, the method comprising:

• forming a first dielectric layer on a substrate;
• depositing a pre-doped P-type doped polysilicon region on the first dielectric layer;
• depositing a pre-doped N-type doped polysilicon region on the first dielectric layer and adjacent to the pre-doped P-type doped polysilicon region;
• and
• forming an isolation region that separates perimeters of the pre-doped P-type doped polysilicon region and the pre-doped N-type doped polysilicon region.