How perovskites can live long and prosper

One of my favourite graphics is a visual paean to scientific and technological progress. Curated by the US National Renewable Energy Laboratory, it charts all of the record-breaking efficiencies of various kinds of photovoltaic cells, noting where and when they were achieved.

Most of the lines on the graph have gentle gradients that indicate slow and steady progress over decades of work. But look down at the bottom right of the graph, and you’ll see a different story: a red line, interspersed with yellow spots, shooting upwards out of nowhere at a bold 60° angle. These are perovskite cells, based on semiconductors such as methylammonium lead halides. The technology has made spectacular progress over the past decade and now boasts a champion efficiency of more than 22%, on a par with the best commercial silicon cells.