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Silica Nanosphere Textured Back Reflectors for Increased Absorption in Thin Film Amorphous Silicon Solar Cells

Lewis@, Brian (2010) Silica Nanosphere Textured Back Reflectors for Increased Absorption in Thin Film Amorphous Silicon Solar Cells. Masters thesis, Iowa State University.

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Abstract

Absorption of long-wavelength photons in thin-film hydrogenated amorphous silicon (a-Si:H) solar cells is inherently low due to an absorption layer thickness of 250-300nm and long absorption lengths for photons of wavelengths above 700nm. When used in a thin-film solar cell, back reflectors that exhibit diffuse reflection increase the probability of absorption by lengthening the path-lengths of photons. Ordered monolayers of silica nanospheres coated with a reflective surface were investigated for use as a diffuse back reflector. A method for fabricating a monolayer of silica nanospheres was developed using a custom built dip-coating apparatus. Repeatable monolayers of 500nm nanospheres were fabricated on glass and stainless steel substrates. The monolayers were covered with a 200nm layer of silver (Ag) and a 200nm layer of aluminum-doped zinc oxide (ZnO:Al) to be used as a back-reflector in a-Si:H solar cells. The back-reflector substrates were measured to have a much higher percentage of diffuse reflectance when compared to flat silver back-reflector substrates. Increases in long-wavelength absorption were observed by normalized external quantum efficiency (NEQE) measurements of the a-Si:H solar cells. Short circuit current density increases were seen in both I-V measurements under AM1.5 lighting as well as in NEQE measurements.

EPrint Type:Thesis (Masters)
Uncontrolled Keywords:Solar Cells nanospheres back reflector
Subjects:Electrical Engineering > MICROELECTRONICS & PHOTONICS > Solar Energy Conversion Materials and Devices
Electrical Engineering > MICROELECTRONICS & PHOTONICS > Semiconductor Materials & Devices Processing
Electrical Engineering > MICROELECTRONICS & PHOTONICS > Photonics
ID Code:549
Identification Number:Identification Number UNSPECIFIED
Deposited By:Mr. Brian Lewis
Deposited On:21 April 2010

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