  The formation of the electron-phonon induced bipolaron is shown to be
feasible in organic semiconductors at the interface with dielectric gates due
to the coupling of the carriers with interface vibrational modes and to the
weak to intermediate strength of bulk electron-electron interaction. The
polaronic bound states are found to be quite robust in a model with realistic
strengths of electron coupling to both bulk and interface phonons. The
crossover to nearly on-site bipolarons occurs for coupling values much smaller
than those for nearly on-site polarons, but, on the other hand, it gives rise
to an activated behavior of mobility with much larger activation energies. The
results are discussed in connection with rubrene field-effect transistors.
