Document Type
Thesis - University Access Only
Award Date
2011
Degree Name
Master of Science (MS)
Department / School
Electrical Engineering and Computer Science
Abstract
Second generation thin film solar cell devices have been gaining market sharing due to inherently lower production costs as compared to crystalline Si-based solar cells. Wide band gap chalcopyrite solar cells, most prominently Cu(l,Ga)Se 2 (CIGS) and CdTe cells, show higher efficiencies than that of amorphous silicon solar cells and have been shown to be alternatives to silicon. However the limited availability of In and toxicity of Cd have hindered their successful commercial application. Group 111-V compound semiconductors are of interest as they can be fabricated to modulate the band-gap in solar cells. AlSb is one of the most promising binary compound semiconductors due to its band gap which is ideal for harvesting most visible photons with a theoretical efficiency of 28%. Both Al and Sb are abundant in nature and relatively inexpensive. This thesis describes the growth of AlSb thin films from Al and Sb and the fabrication of solar cell devices using AlSb as an absorber layer. Al and Sb targets were co-sputtered at various power to make AlSb compound semiconducting films. The material structure and optical/electrical properties of the film showed a strong dependence on sputtering power, temperature and duration of thermal treatment process. Optimized films had absorption coefficients in the order of 10 4 cm- 1 making them suitable absorbers for solar cells. Solar cell model that included a mid-gap Gaussian and surface tail state defects resulted in a conversion efficiency of 14%. The fabricated p-i-n junction solar cells had a conversion efficiency to 0.1 %. This low efficiency was attributed to very high defect states at the interface of AlSb with the p and n type layers. Future work should focus on reducing interface trap states by improving morphology and crystallinity of the films and exploring doping materials for n-type Al Sb to generate a stronger built in field for charge separation.
Library of Congress Subject Headings
Thin films
Solar cells
Compound semiconductors.
Format
application/pdf
Number of Pages
104
Publisher
South Dakota State University
Recommended Citation
Dhakal, Rabin, "AlSb Compound Semiconductor as Absorber Layers in Thin Film Solar Cells" (2011). Electronic Theses and Dissertations. 1777.
https://openprairie.sdstate.edu/etd2/1777