Clean-tech companies are always betting on the future. But First Solar is the rare green company that is making a killing right now. The Phoenix-based thin-film solar panel manufacturer, launched with money from Wal-Mart's Walton family, began commercial production of its inexpensive solar modules back in 2002, ahead of most competitors — since then, First Solar has gone from strength to strength. It already dominates the emerging thin-film solar industry, and in 2006 the company went public in one of the strongest IPOs yet in the clean-tech sector. Shares that initially went for $20 are now worth almost $300, with no upper limit in sight. While its competitors have struggled with the tricky process of mass-producing thin-film panels, First Solar — with factories in Arizona, Germany and eventually Malaysia — will soon crack the 1 gigawatt barrier in solar production. "We can deliver at price and we can deliver at volume," says Mike Ahearn, First Solar's CEO. "But there's still room for continuous improvement."