Nano Lett. 16, 7461–7466 (2016)

In conventional energy harvesting devices, steady power output is achieved via active feedback components such as voltage converters. The same requirement applies to solar cells that are not equipped with any internal regulation mechanism to account for natural variations in the incident solar power. This long standing issue of inefficient energy storage has now been addressed by Arp and colleagues, who propose a model describing a quantum heat engine photocell with an intrinsic mechanism for the suppression of energy fluctuations.

Similar to the case of photosynthesis in green plants, a heat engine with quantized energy levels converts the energy of solar photons into useful work. In the simplest case, a nanoscale light-harvesting photocell consists of two photon-absorbing channels with equal charge transfer probability but different energy input. When exposed to fluctuating solar energy, the quantum heat engine photocell stochastically switches between high and low power channels to yield steady-state output. Simulations reveal that this suppression mechanism is effective over a wide range of the solar spectrum with the exception of the green region, in which the regulatory benefits vanish and the two-channel quantum heat engine essentially behaves as a one-channel photocell.