  Studies of emerging photovoltaics, such as organic and perovskite solar
cells, have recently shown that the separation of photo-generated charge
carriers is correlated with non-thermal, coherent oscillations within the
illuminated device. We consider this experimental evidence in light of results
from the theory of open quantum systems that point to the need for a
self-oscillating internal capacitor, acting as a microscopic piston, to explain
how an illuminated solar cell operates as an autonomous heat engine. We propose
a picture of work extraction by photovoltaic devices that supersedes the
quasi-static descriptions prevalent in the literature. Finally, we argue that
such a dialogue between condensed matter physics and quantum thermodynamics may
offer a guide for the design of new energy transducers.
