A quantitative study of n-type doping in highly crystalline organic semiconductor films establishes the predominant influence of electrostatic forces in these low-dielectric materials. On the basis of these findings, a self-consistent model of doped (purposely or not) organic semiconductors is proposed in which the equilibrium free carrier density, n(f), is a small fraction of the total charge density, a superlinear increase in conductivity with doping density is universal, n(f) increases with applied electric field, and the carrier mobility is field dependent regardless of crystallinity.