Effects of polarons and bipolarons on spin polarized transport in an organic device

A polaron–polaron interaction model is suggested to study the spin injection and transport in an organic semiconductor (OSC) device. The evolutions of spin polarons and spinless bipolarons are calculated from the drift-diffusion equations, in which both the polaron–bipolaron transition and the spin-flipping of a spin polaron are included. Then the spin polarized current is obtained. It is found that the polarons are responsible for the spin polarized transport in an OSC. Different from the case in a normal inorganic semiconductor, spinless bipolarons will affect the spin polarization of the OSC device. Finally, effects of the spin-flip time and the mobility of the carriers on the spin polarization in an organic device are discussed.