This work suggests a new mechanism for the spontaneous formation of interlayers in OPVs. The process is based on the migration of additives to the organic/metal interface driven by the chemical interaction between the additive and the evaporated metal atoms. The additive/metal interactions also modify the effective electrode work function and dramatically improve the OPV device performance. Importantly, this research shows that introducing the new polymer/metal interface during the electrode deposition could overcome the free surface energy consideration and alter the polymer/metal interfacial composition. Indeed, we have shown that chemical interactions between specific end groups of an organic additive, poly ethylene glycol (PEG), induces its migration to the blend/metal interface. The migration was utilized to place molecules with a dipole moment at the organic/metal interface, and thus change the electrode workfunction. The research results and the detailed understanding of the metal evaporation-induced migration open new opportunities for better control of charge extraction in OPVs, yielding selection criteria for the design of improved organic devices.