Comparison of spin and charge transport in organic semiconductors

We have investigated spin and charge transport processes in organic semiconductors (OSECs) in order to compare spin-transport and charge-transport in these materials. For the spin transport we measured the spin diffusion length, λs via the inverse spin Hall effect (ISHE) in NiFe/OSEC/Pt trilayer devices, whereby a pure spin-current is generated in the polymer by spin-pumping from the ferromagnetic layer (NiFe), then diffuses to the Pt layer where it is converted into an electrical signal due to the strong spin-orbit coupling of Pt. For the charge transport we measured the carrier mobility of photogenerated charges via the time of flight technique. We also determined the (longitudinal) spin relaxation time, T2 by pulsed EPR method, which allows us to calculate the spin diffusion coefficient Ds from λs. Finally we relate Ds to the charge diffusion coefficient Dc, which is determined from the charge mobility measurements via the time-of-flight method.