Charge transfer and singlet fission quantum dynamics in organic photovoltaics

We will discuss our recent investigations on singlet fission and charge separation quantum dynamics in organic photovoltaic devices. First, we use a real-time path-integral approach to explore the singlet fission processes in pentacene. We observed destructive interference effects between the two charge transfer (CT) mediated fission pathways due to their opposite electronic couplings with the triplet-triplet pair state. Second, we apply an approximated quantum dynamics approach to investigate the competing charge transfer and charge separation pathways in organic photovoltaic (OPV) bulk heterojunction (BHJ). This approach propagates the time-dependent electronic wavefunction on a pre-computed molecular dynamics trajectory. The electronic wavefunction is expanded with instantaneous Density Functional Tight Binding (DFTB) orbitals along the nuclear trajectory. This approximated approach allows us to characterize the real-time electron and hole dynamics in a realistic large-scale BHJ model system and resolve the mechanistic debates on free charge carrier generations in OPV devices.