Quantum Two-Level Model for Excitonic Solar Cells

While improving the performance of excitonic solar cells (XSCs) has been a central effort of the scientific community for many years, theoretical approaches facilitating the understanding of electron-hole interaction, recombination and electron-phonon coupling effects on the cell performance are still needed. We present a novel simple model which is based on the quantum scattering theory, in particular on the Lippmann-Schwinger equation; this minimizes the complexity of the problem while providing useful and non-trivial insight into the mechanism governing photocell operation. In this formalism, both exciton pair creation and dissociation are treated in the energy domain, and therefore there is access to detailed spectral information, which can be used as a framework to interpret the charge separation yield. Our analysis helps to optimize the charge separation process and the energy transfer in excitonic solar cells.