Degree Type

Thesis

Date of Award

2009

Degree Name

Master of Science

Department

Electrical and Computer Engineering

First Advisor

Vikram Dalal

Abstract

Silica microspheres were investigated as a back surface texturing agent for hydrogenated amorphous (a-Si:H) and nanocrystalline (nc-Si:H) silicon solar cells. Absorption of long wavelength photons (>600nm) is minimal for a-Si:H and nc-Si:H thin films which limits the efficiency of thin-film solar cells. Textured back reflectors are often used to increase the efficiency of these solar cells by diffusely reflecting light and trapping it in the absorbing layer.

In this research, stainless steel substrates were spin coated with silica spheres to add texture. After a post-anneal, silver was deposited on the substrates. Two sphere diameters (250nm and 500nm) were investigated for their impact on diffuse reflection versus wavelength. It was found that the peak in diffuse reflection could be controlled by varying the sphere diameter. The thickness of the silver layer was determined by maximizing the total reflection, and diminishing returns were found for a silver layer greater than 300nm.

External quantum efficiency measurements were used to characterize carrier collection versus wavelength. An increase in carrier collection at long wavelengths (>600nm) was observed for both a-Si:H and nc-Si:H solar cells on the silica sphere textured substrates. The thin a-Si:H solar cells often shorted out during testing which limits the industrial application of this back reflector. Shorting was not found to be a problem with the nc-Si:H devices.

DOI

https://doi.org/10.31274/etd-180810-54

Copyright Owner

Ryan Boesch

Language

en

Date Available

2012-04-28

File Format

application/pdf

File Size

58 pages

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