  We evaluate entropy production in a photovoltaic cell that is modeled by four
electronic levels resonantly coupled to thermally populated field modes at
different temperatures. We use a formalism recently proposed, the so-called
multiple parallel worlds, to consistently address the nonlinearity of entropy
in terms of density matrix. Our result shows that entropy production is the
difference between two flows: a semiclassical flow that linearly depends on
occupational probabilities, and another flow that depends nonlinearly on
quantum coherence and has no semiclassical analog. We show that entropy
production in the cells depends on environmentally induced decoherence time and
energy detuning. We characterize regimes where reversal flow of information
takes place from a cold to hot bath. Interestingly, we identify a lower bound
on entropy production, which sets limitations on the statistics of dissipated
heat in the cells.
