Solar Cell Design, Fabrication, and Characterization

David Wagner, Chris Baber

Abstract


Given the growing attractiveness of alternative energies, the goal of this research project is to gain a better understanding of the photovoltaic effect through the design, fabrication, and characterization of silicon solar cells. First discovered in 1839, the photovoltaic effect is the conversion of optical energy into electrical energy. A common device used to realize the photovoltaic effect is the silicon solar cell. Through basic semiconductor fabrication techniques, silicon wafers are processed to create a layered structure known as a pn junction – the foundation of a solar cell. A pn junction is formed by the diffusion of different dopants or impurities into the silicon in order to affect its electrical characteristics. Depending on the diffusion time and temperature, the structure and electrical characteristics of the pn junction, and the resulting performance of the solar cell, will vary significantly. For example, a longer diffusion at a higher temperature may produce a more conductive path for the flow of the photocurrent (electrical current produced by the incident solar energy); however, these processes may also increase the depth of the pn junction into the silicon wafer, making it more difficult for the optical energy to penetrate down to the junction. Similarly, a larger electrical contact may enhance the electrical performance of the solar cell (lower contact resistance); however it can also reflect more optical energy away from the solar cell. In our study, several semiconductor wafers are processed using different dopant materials, different dopant diffusion times and temperatures, and varying electrical contact designs in order to find the configuration that provides the best photovoltaic performance.

Keywords


Solar, Fabrication, Cell Design

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