diffrent types of back contacts/solar cells

hi friends,i need a help to finding types of back contacts in thin film solar cells!in a ms level!

Maybe this can help:


How Thin-film Solar Cells Work (Described on 5 pages)
http://science.howstuffworks.com/env...olar-cell3.htm


Thin-film solar cells: review of materials, technologies and commercial status
http://copilot.caltech.edu/classes/a...eview_2007.pdf