Electron mobility measurement using exciplex-type organic light-emitting diodes

A method to measure the electron mobility in organics is demonstrated. Bilayer organic light-emitting diodes composed of donor-type and acceptor-type materials often show exciplex emission. We employed a triphenyldiamine derivative and an oxadiazole derivative (PBD) as hole and electron transporters, respectively, and confirmed that the emission is from exciplex. From the transient response of the device after application of pulsed voltage, the electron mobility of neat PBD film was evaluated to be ${\text{2.0×10}}^{\text{−5}}\hspace{0.17em}{\mathrm{cm}}^2/\mathrm{V s}$ under the electric field of 1 MV/cm.