Date of Award

Fall 12-2018

Level of Access Assigned by Author

Open-Access Thesis

Degree Name

Master of Engineering (ME)

Department

Physics

Advisor

Rosemary L. Smith

Second Committee Member

Scott D. Collins

Third Committee Member

Robert W. Meulenberg

Abstract

The goal of this project is to design and develop a fabrication process for a silicon photovoltaic device which incorporates a nanohair textured p-n junction. The silicon nanowires are etched into a silicon wafer, comprising an epitaxial p-layer on n-substrate, via metal-assisted chemical etching (MACE). The resulting nanowires contain p-n junctions that lie along the length of the vertical nanowires. This construct has the potential to increase the optical bandwidth of a silicon photovoltaic device by allowing a greater amount of short wavelength light to reach the junction. In addition, the MACE method of nanofabrication has the potential for decreasing the manufacturing complexity and related costs by eliminating the need for photolithographic patterning.

The fabrication procedure is presented, along with material and morphological characterization of the finished device. Device fabrication considerations include inter-nanowire material, ohmic electrical contacts, and device passivation. Current vs voltage characteristics of the nanowire device are presented and compared to its planar analog.

Nanohair textured and planar device performance are compared under illumination of varying wavelength and intensity. Nanohair textured devices are found to increase electron-hole pair generation under solar simulated and blue light illumination with more significant gains found for blue light illumination. This increased electron-hole pair generation is attributed to an increased amount of short wavelength light reaching the p-n junction. However, nanohair textured devices are found to have more significant surface recombination effects than planar devices that limit the nanohair textured device efficiency under low intensity illumination. Both planar and nanohair textured devices are found to have limited efficiency under intense illumination due to series resistance effects.

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