Bilevel contact solar cells
AssigneeThe Board of Trustees of the Leland Stanford Junior University
InventorRonald A. Sinton
Life of this patent
Estimating the term…
Abstract
A high efficiency back side contact solar cell is fabricated using a self-aligning process that reduces the number of masks and alignments as compared with prior processes. The back surface of the cell is patterned by etching into an array of bilevel, interdigitated mesas and trenches, separated by inclined surfaces. Doping of the back surface region produces laterally alternating and overlapping P and N regions associated with the mesas and trenches. A metalization layer is deposited over the entire back side of the cell. The portions of the metalization on the inclined surfaces are readily removed by etching. Removal of the metalization on the inclines surfaces separates the mesa conductors from the trench conductors, leaving a well defined interdigitated array of positive electrodes and negative electrodes.
Claims14
A solar cell, comprising:
- a body of a semiconductor material having at least one P/N junction therein, the body including
- a front face having no electrodes thereon, and
- a bilevel elevation back face having at least one P-doped region at a first level interdigitated with at least one N-doped region at a second level, wherein the at least one P-doped region and the at least one N-doped region partially overlap to form at least one compensated region;
- and
- a positive electrode contacting the at least one P-doped region and a negative electrode contacting the at least one N-doped region, both electrodes contacting the solar cell on the back face.
A process for preparing a solar cell, comprising the steps of:
- providing a body of a semiconductor material;
- forming laterally alternating mesas and trenches on a back face of the semiconductor body, there being an elevational transition region between each mesa and the adjacent trench;
- doping the back face of the semiconductor piece so that P/N junctions are formed between the material below the mesas and the material below the trenches;
- depositing a metalization layer overlying the back face of the semiconductor piece;
- and
- removing the portion of the metalization layer deposited upon the transition region between the mesas and trenches without applying a mask to effect the removal.
A process for preparing a solar cell having back side positive and negative electrical connections, and no electrical connections on the front side of the solar cell, comprising the steps of:
- providing a body of a semiconductor material having a front face and a back face;
- placing a mask onto the back face, the mask having therein an interdigitated pattern of masked and unmasked regions;
- forming a pattern of trenches in the back face through the unmasked regions with mesas between the trenches and elevational transition regions between each mesa and the adjacent trench;
- and
- providing a metalization layer on the tops of the mesas and the bottoms of the trenches, but not in the elevational transition regions, the step of providing a metalization layer to occur without any photolithographic masking of the cell.
A process for preparing a solar cell, comprising the steps of:
- providing a body of a semiconductor material having a front face and a back face;
- depositing a layer of a mask material onto the back face, the mask material having a first dopant therein;
- patterning the mask to form a pattern of elongated openings therethrough;
- transferring the mask pattern to the back face of the body of semiconductor material to form a pattern of laterally adjacent mesas and trenches in the back face, the mesas and trenches being separated by regions inclined at an angle from the normal to the trench bottom;
- diffusing first dopant from the mask material into the mesas;
- removing the mask;
- depositing a metalization layer onto the back face;
- and
- etching the metalization layer by an amount sufficient to remove that portion overlying the inclined regions but not those portions overlying the mesas and the trenches.
Dependencies are inferred from the claim text.