BS in Materials Engineering
Materials Engineering Department
Richard N. Savage
As the energy of fossil fuel supplies are fast depleting due to high consumptions of energy by human beings, the need for other sources of energy, such as solar energy, has become a viable option. By creating solar cell arrays the desired voltage can be generated. The overall goal of the Solar Ear project is to create an array of photovoltaic cells connected with aluminum tracings to recharge batteries that are specifically used for hearing aids. The goal embodies two main areas: the design of a processing method to connect the cells during a micro-fabrication process and the creation of an array that produces enough voltage and current to power low-power applications like a hearing aid battery recharger. We have successfully designed and fabricated a device with two cells connected in series thus far to make sure the interconnections in our design were capable of connecting cells in an array. An aluminum bridge across an insulating channel of SU-8 was created as an interconnection to connect both cells on the silicon-on-insulator (SOI) wafer. Although we successfully addressed the first goal to connect the cells, this two-cell device did not produce the desired voltage and current. To address this problem we optimized the manufacturing process by creating larger doped regions and forming an oxide over the wafer surface with vias to create the aluminum contacts. These modifications were enacted during spring quarter when we fabricated a 12-cell device. These final devices exhibited good cell interconnection and a maximum of 5.5V was obtained from one of the final wafers. The current produced by these devices, however, was nearly 10 times less than expected and failed to reach the levels necessary to charge a hearing aid battery.