Date of Award
Master of Science
Electrical and Computer Engineering
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.
Brian Wellington Lewis
Lewis, Brian Wellington, "Silica nanosphere textured back reflectors for increased absorption in thin film amorphous silicon solar cells" (2010). Graduate Theses and Dissertations. 11466.