Abstract

Conventional solar cells generate one electron for each absorbed photon. Any excess photon energy above the bandgap is wasted as heat. This leads to the Shockley-Queisser efficiency limit of 34% for solar cells containing a single semiconductor junction. Singlet exciton fission splits a high-energy singlet exciton into a pair of low-energy triplets. In solar cells, it promises to double the electricity generated from the blue part of the sunlight, breaking the single junction efficiency limit. ​Moving toward the goal of developing solar cells that overcome the Shockley-Queisser limit, we demonstrate fission-based photovoltaic cells that produce more than one electron per incident photon. It is the first time that any solar cell has shown the photon-to-electron conversion efficiency exceeding 100% in the visible spectrum. Continuous advances in fission-based photovoltaics require understanding the fundamental mechanism governing singlet fission. We present a universal model that successfully predicts the rate of fission and confirm that fission is robust to variations in molecular morphology.