Organic solar cells (OPVs) continue to see striking increases in efficiencies, with some research cells exceeding 8% power conversion efficiency, and module efficiencies approaching or exceeding ca. 4%.[1-3] These efficiencies are not yet adequate to create a PV technology which hits the DOE target of $1 per watt (peak), but there is reason for optimism that the low materials costs of this technology will drive it to this goal, provided that both efficiencies and lifetime can be improved. Contact and interlayer materials are a critical feature of OPVs that require significant optimization for both single-junction and for tandem OPV platforms. This paper provides a brief overview of new interlayer materials, how they function, their limitations, and surface and interface science approaches to their optimization.