What is the environmental impact of making solar cells?
The term "solar cell" refers to a wide variety of technologies[1]. Anything from common semiconductors, rare-earths or even fruit juice can be used to make solar cells. The impact will be highly dependent on the type of cell in question.
[1]:http://www.nrel.gov/ncpv/images/efficiency_chart.jpg
The above graph isn't all-encompassing.