Researchers at the University of Cambridge have uncovered a rare quantum effect in an organic semiconductor once thought possible only in metals. The study, centered on the spin-radical material P3TTM, showed that when its molecules pack closely together, unpaired electrons interact in a pattern resembling Mott-Hubbard behavior. This interaction allows light to trigger efficient charge separation, producing electricity with minimal loss. In lab tests, a solar cell made from a thin film of P3TTM achieved near-perfect charge collection efficiency. Unlike conventional organic solar cells that rely on two materials, this system converted light to electricity within a single substance. The breakthrough emerged through collaboration between Cambridge’s Chemistry and Physics Departments.