Charge separation and recombination in organic photovoltaic devices predominantly occurs at interfaces between electron donor (D) and electron acceptor (A) polymers or molecules. With this in mind, the molecular nature of this interface is expected to play a pivotal role in determining the relative rates of charge separation and recombination. For example, factors such as molecular energetics and electronic coupling will all depend on the molecular nature of the interface. Unfortunately, the molecular details of D-A interfaces are inherently difficult to investigate and thus much remains unknown as to what interfacial properties promote efficient charge separation. In the case of high-efficiency polymer-fullerene systems, where the electron donor is a conjugated polymer and the electron acceptor is a fullerene, a structural trend emerges that appears to favor a specific polymer-fullerene arrangement. Namely, many OPV donor polymers tend to be based on a donor-acceptor structure, whereby an electron rich “donor” unit is copolymerized with an electron deficient “acceptor” unit, and it is within these systems where the structural trend is prevalent. That is the polymer tends to have a branched substituent on the donor moiety and a linear or no substituent on the acceptor moiety, thereby making this acceptor unit more sterically accessible to the fullerene. The prevalence of this structural trend led us to hypothesize that a more favorable polymer-fullerene conformation occurs when the fullerene is in closer proximity and interacting more strongly with the acceptor moiety than the donor moiety. Through a series of PBDTTPD polymers designed to sterically favor various polymer-fullerene arrangements, we show that fullerene docking with the acceptor moiety leads to the highest performing devices. This conclusion is supported through a series of experiments including device studies with vastly different aggregation states of the polymer, charge-transfer state absorbance measurements, and solid-state two-dimensional heteronuclear correlation (HETCOR) NMR analyses. This work, combined with further future studies exploring why this molecular arrangement is beneficial, is likely to facilitate the intelligent design of novel high-performing conjugated polymers.