the scientists favored a methodical process in which each step brings increased understanding of their new device and the underlying physics, while the venture capitalists pushed hard for quick results. After that, Naughton says, the pair discussed the nanocoax almost every day, eventually leading to another crucial insight: The nanocoax-based solar device could solve the problem that makes conventional solar cells so inefficient—the thick-thin problem. today’s commercial solar cell, the kind that makes up the solar panel installed atop your neighbor’s roof, consists of a slab of silicon sandwiched between two metal electrical conductors, the top conductor in the form of a grid. When light penetrates the grid and hits the silicon, it knocks an electron off each silicon atom it impinges on, so that light energy is converted to electrical energy. Ideally, each electron thus freed would migrate to one of the metal conductors, and thus an electrical current would flow. In the real world, however, this happens rarely, with most electrons simply wandering around in the silicon, never getting as far as the conductor. That’s where the thick-thin dilemma comes in. The thicker the silicon, the less likely it is that the electrons will be harvested—will make it out of the silicon and contribute to the flow of electrical current. The thinner the silicon, however, the less light the cell is likely to absorb in the first place, and thus the fewer free electrons available for harvesting. Traditional solar cells, then, represent a compromise, their silicon thick enough to absorb a modest amount of light but thin enough to allow the harvesting of a modest number of electrons. Because of this compromise, their efficiency—the proportion of available light they convert to electricity— ranges from less than 5 percent to a still-low 30 percent. The nanocoax-based solar cell would work quite differently, absorbing light along the nanotube’s 10,000-nanometer length (thick) while allowing the electrons to migrate to the metal layers across the tube’s 50-nanometer radius (thin). The design represented not a compromise but something much closer to optimal dimensions, both for light absorption and electron harvesting. Moreover, the design should work equally well with the cheap amorphous form of silicon as with the pricier crystalline form. Kempa’s notion, then, promised to turn the photovoltaics world on its head. kempa and his colleagues thought enough of the idea to fool with it in the laboratory. In late 2005,
Kempa, with help from Naughton, wrote a proposal for grant money in a competition run by a state agency, the Massachusetts Technology Transfer Council; the proposal was funded for $25,000. The physicists, along with Jakub Rybczynski, a postdoctoral fellow from Poland, entered a second contest, the Ignite Clean Energy Business Plan Competition, sponsored by the MIT Enterprise Forum. In May 2006, the announcement came that the new solar cell design had taken second place, with a prize of cash and inkind support valued at $35,000. That spring, Kempa, Ren, and Naughton incorporated as Solasta. The name came from Solas, a bar in Boston’s Back Bay neighborhood where Naughton had recently stopped in for a beer. More important than the remittances, the wins attracted venture capitalists. The technology drew so much interest, in fact, that for two months in early 2006, between in-person visits and telephone calls from some 20 venture capital firms, the physicists were “ready to drop,” said Naughton, who had emerged as the group’s informal leader. “It’s crazy! We can’t get rid of them,” Kempa groused. What was scheduled to be a 10-minute call with one suitor, he said, turned into an hour: “It started with ‘That’s very interesting. I’ll send someone out’ and ended with ‘I’m coming out tomorrow!’” This particular investor, though, wasn’t one whom the physicists wanted to be rid of. Bill Joy was something of a legend in his field, touted in the business press as “the Edison of the Internet” for his visionary software. In Silicon Valley, writes Malcolm Gladwell in his 2008 book Outliers, Joy engendered the same awe as Microsoft’s Bill Gates, having played a central role in developing the Java programming language as well as Berkeley Unix, ancestor of the Unix operating system. In 2005, figuring that green technology was the economy’s next big act, Joy had become a partner in Kleiner Perkins Caulfield & Byers—KP, for short. This was a venture capital firm with the foresight to have bankrolled Amazon and Google in those corporations’ infancy. In June 2006, the Boston College physicists signed a term sheet, an agreement whereby KP would invest $4 million in exchange for preferred stock amounting to half of their company. Interviewed that August, Naughton explained that he liked KP’s deep Rolodex. “They can bring in expertise on . . . technical problems that we don’t see but anticiw i n t e r 2011 v b c m
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