Solar cell and method of fabrication thereof
A solar cell and a method of fabricating solar cells. The method includes a step of separating neighbor solar cells formed on a semiconductor wafer by scribing the wafer to form scribe lines on the wafer and applying a force at, or adjacent to, the scribed lines to separate the solar cells. The scribing is effected on a cap layer covering a window layer of solar cells, thereby minimizing damage to the window layer and mitigating propagation of defects into p-n junctions formed in the solar cells.
1. A solar cell made of semiconductor materials, the solar cell having a crystalline structure with crystal planes, the solar cell comprising:
a germanium substrate;
a least one p-n junction formed atop the germanium substrate, the at least one p-n junction including one or more group III elements and one or more group V elements;
a solar cell window layer formed atop the at least one p-n junction;
a patterned cap layer formed atop the solar cell window layer, the patterned cap layer being electrically connected to the solar cell window layer, the patterned cap layer exposing a light-input portion of the solar cell window layer;
a sidewall extending along a height of the cap layer and towards the germanium substrate, the sidewall having a cleaved surface, the cleaved surface being parallel to a cleaving plane of the solar cell, the cleaving plane being parallel to a crystal plane of the solar cell, the crystal plane being a plane of a (110) family of planes of the crystalline structure;
a side piece adjacent the sidewall, the side piece being a semi-insulating silicon side piece; and
a metal layer formed on a portion of the patterned cap layer and on a portion of the side piece, the metal layer defining a busbar of the solar cell, the busbar bridging the side piece and the patterned cap layer.
2. The solar cell of claim 1 further comprising a metal layer formed on a portion of the patterned cap layer.
3. The solar cell of claim 2 wherein a portion of the metal layer defines a busbar of the solar cell.
4. The solar cell of claim 3 wherein the solar cell window layer includes aluminum indium phosphide, the cap layer includes gallium arsenide, and at least one of the at least one p-n junction includes indium gallium arsenide.
5. The solar cell of claim 4 wherein the patterned cap layer further includes indium.
6. The solar cell of claim 1 wherein the at least one p-n junction, the solar cell window layer, and the patterned cap layer are pseudomorphic with the germanium substrate.
7. The solar cell of claim 1 wherein the germanium substrate is a vicinal substrate having a vicinal angle comprised between 0° and 20°.