  We introduce a top-ranked cycle flux ranking scheme of network analysis to
assess the performance of molecular junction solar cells. By mapping the
Lindblad master equation to the quantum-transition network, we propose a
microscopic Hamiltonian description underpinning the rate equations commonly
used to characterize molecular photocells. Our approach elucidates the
paramount significance of edge flux and unveils two pertinent electron transfer
pathways that play equally important roles in robust photocurrent generation.
Furthermore, we demonstrate that non-radiative loss processes impede the
maximum power efficiency of photocells, which may otherwise be above the
Curzon-Ahlborn limit. These findings shed light on the intricate
functionalities that govern molecular photovoltaics and offer a comprehensive
approach to address them in a systematic way.
