Self-Stimulated Dissociation in Non-Fullerene Organic Bulk-Heterojunction Solar Cells

This paper reports self-stimulated dissociation occurring at donor:acceptor interfaces in non-fullerene solar cells to completely separate electron-hole pairs toward developing high-efficiency photovoltaic actions. By monitoring in situ, the dissociation at D:A (PM6:Y6) interfaces with magnetic field effects of the photocurrent, it was observed that, as the excitons are increased by gradually increasing photoexcitation intensity, the dissociation at D:A interfaces becomes surprisingly easier, once the non-fullerene Y6 molecules are optically excited. This presents a self-stimulated dissociation phenomenon identified by gradually increasing light illumination, while monitoring the dissociation with magnetic field effects of the photocurrent. Our photoexcitation-dependent magneto-capacitance at 1 MHz found that optically exciting the Y6 molecules generates a dipolar polarization signal, leading to a light-induced bulk polarization in the PM6:Y6 system. Essentially, the self-stimulated dissociation is enabled by optically excited non-fullerene Y6 molecules with photoinduced dipolar polarization to completely separate electron-hole pairs at D:A interfaces toward developing high-efficiency photovoltaics in non-fullerene organic solar cells.