Effect of bipolarons on spin polarized transport in magnetic permeated sublayer of organic spin device

According to the permeation phenomenon of magnetic atoms in organic device, such as Co/organic semiconductor (OSC)/La0.7Sr0.3MnO3, the evolution of spin polarons and spinless bipolarons are calculated with the drift-diffusion equations to investigate the effect of polaron-bipolaron interaction on spin polarized transport in a magnetic permeated sublayer (MPS). It is found that the MPS has different spin-flip time and mobility from those in pure organic semiconductor. The splitting of spin-flip time will be adjusted by the effect of the magnetization of the impurity atoms. Mobilities of spin carriers in the MPS will be reduced due to the scattering of the Co atoms. Both the spin-flip time and the mobility will affect the polaron-bipolaron interaction and further influence the spin polarized transport. It is found that the splitting of spin-flip time is the main factor responsible for the spin relaxation, while the polaron-bipolaron interaction is the secondary factor.