Natural and artificial light harvesting systems often operate in a regime where the flux of photons is relatively low. Besides absorbing as many photons as possible it is therefore paramount to prevent excitons from annihilation via photon re-emission until they have undergone an irreversible conversion process. Taking inspiration from photosynthetic antenna structures, we here consider ring-like systems and introduce a class of states we call ratchets: excited states capable of absorbing but not emitting light. This allows our antennae to absorb further photons whilst retaining the excitations from those that have already been captured. Simulations for a ring of four sites reveal a peak power enhancement of 35% under ambient conditions owing to a combination of ratcheting and the prevention of emission through dark state population. In the slow extraction limit the achievable current enhancement exceeds hundreds of percent.
Higgins, K. D. B., Lovett, B. W., & Gauger, E. M. (2017). Quantum-enhanced Capture Of Photons Using Optical Ratchet States. Journal of Physical Chemistry C, 121(38), 20714–20719. https://doi.org/10.1021/acs.jpcc.7b07138