Controllable bipolaron formation unveiling structural features of trap states in organic charge transport

Magnetic resonance methods offer a unique chance for in-depth study of conductive organic material systems, not only accounts for number of charge carriers, but also allows manipulations of spin dynamics of particles. Here we present a study of continuous-wave electrically detected magnetic resonance on a range of organic conjugate polymers under transistor architecture, with tunability in both carrier concentration and drifting electric field. We demonstrate the general existence of bipolaron between mobile and trapped charges at the magnetic resonance condition, then estimates the wavefunction expansion of charge carriers on their hopping sites along conductive pathways. This finding allows direct observation of energetically disordered trap sites under the charge hopping picture, linking-up the microscopic structural properties to the bulk electronic performances.