Hole Transfer Promoted by a Viscosity Additive in an All-Polymer Photovoltaic Blend

摘要： Viscosity modi?ers are widely applied to improve the mechanical compliance of organic optoelectronic devices. However, the e?ect of the viscosity additives on the charge dynamics remains poorly understood. Here, we report the observation of markedly di?erent e?ects of a high-viscosity polymeric additive on the electron- and hole-transfer dynamics in all-polymer organic photovoltaic blends. By using ultrafast transient absorption spectroscopy, we determine that hole transfer from charge-transfer excitations in the acceptor is markedly promoted while the electron transfer from local excitations in the donor remains nearly unchanged upon introduction of viscosity additives into the blends. We argue that the modi?cation of dielectric screening is the mechanism underlying the e?ect of the additive on the charge dynamics. This ?nding suggests a new strategy for designing high-performance ?exible organic photovoltaic devices by manipulating the dielectric environment.