Stéphane Kéna-Cohen

A thin film for a solar cell or display is like a dense crowd in a square: each person faces a different direction, and whether light passes through the crowd or gets stuck depends on which way everyone is looking. In organic electronics, molecules play the role of passersby. Until now, instruments could only measure the crowd's overall direction — the average head tilt and its spread.

Organic light-emitting materials are like a busy intersection without traffic lights. Molecules receive energy but, instead of honestly giving it back as light, they often turn into dead ends: they form dark pairs (exciplexes — short-lived complexes that do not emit) or collide with each other, losing charge.