Back in 2008, when the US was deploying less than 300 megawatts a year of solar photovoltaic (PV) panels, and the boom in solar was but a gleam in President Barack Obama’s eye, it was very much an open question which solar technology might triumph in the end, or if any of them would triumph at all. Most solar at the time used old-fashioned crystalline silicon panels, which have been around since the 1950s. But there were hopes for (and some extremely large investments in) mul