How iron carbenes store energy from sunlight—and why they aren't better at it

Photosensitizers are molecules that absorb sunlight and pass that energy along to generate electricity or drive chemical reactions. They're generally based on rare, expensive metals; so the discovery that iron carbenes, with plain old iron at their cores, can do this, too, triggered a wave of research over the past few years. But while ever more efficient iron carbenes are being discovered, scientists need to understand exactly how these molecules work at an atomic level in order to engineer them for top performance.