BS in Materials Engineering
Materials Engineering Department
Two different processes to create multi-celled solar panels from single wafers were made and implemented. To do this, the cells must not have a common ground, and both designs use different approaches to solve this problem. One utilizes a 2.9 µm deep n-type well within a 10.74 µm deep p-type well in an n-type wafer. There are two cells in series, which has a theoretical voltage of 1 V. The cells are connected in series with 1.9 µm thick gold traces. Any area that the gold is not in contact with the silicon has a .5 µm layer silicon dioxide layer in order to keep them separate. The other is made from a p-type silicon on insulator wafer with 2.9 µm deep n-type wells. There are ten cells, which gives a theoretical voltage of 5 V. Each solar cell was separated by etching through the silicon down to the buried oxide layer. This left each cell completely unconnected electrically. The traces were deposited on a glass wafer that attaches to the cells by use of a conductive epoxy. A layer of titanium was deposited first to promote adhesion to the glass, and a 1.9 µm gold layer was deposited on top of that to carry the current. Each panel is tested by measuring the short circuit current, the open circuit voltage, and intermediate points in order to create a graph of the current density versus voltage.