In Part 1 of this article, we looked at how lab and commercial efficiencies are growing in crystalline, CIGS and amorphous solar cells. Now we'll take a look at how increasing efficiencies have boosted cadmium telluride, the thin film made by No. 1 solar manufacturer First Solar. We also examine how cadmium telluride could also help grow the market for multijunction concentrator cells -- the world's most efficient cells -- by making concentrating-photovoltaic projects more cost effective. Efficiency improvements have been accelerating in the last few years as more money, scientists and companies have entered the solar space, according to Martin Green, a professor at the University of New South Wales. Where will these efficiencies ultimately plateau?