In the field of organic photovoltaics, efficiencies beyond 13% have recently been achieved by combining low bandgap conjugated polymers with small-molecule non-fullerene acceptors (NFAs). Besides remarkable efficiency, intriguing properties for these NFAs have been reported. For instance, it has been shown that the donor:acceptor interfacial energy offset is less demanding for charge separation compared to fullerene acceptors, i.e. excitons dissociate efficiently even with a small driving force. In addition, polymer:NFA devices typically show low open circuit voltage (VOC) loss. To further understand what differentiates non-fullerenes from fullerenes in terms of the charge generation and transport processes, we have used ultrafast transient absorption spectroscopy (TAS), electro-modulated differential absorption spectroscopy (EDA) and terahertz measurements (THz). To simplify the complexity of the process due to the phase morphology of bulk heterojunction blends, we have worked with bilayers of the J61 donor polymer with the m-ITIC NFA. Varying the thickness of the layers, the direction of irradiation and the excitation wavelength, we could determine the exciton dissociation rates upon electron and hole transfer, gain insight how those processes are limited by exciton diffusion to the bilayer interface, and target the transport in both materials.