Study of the magnetic field effects on carriers' mobility in polymer based light-emitting diodes

The magnetic field effects on the carriers' mobility have been investigated for poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonat) (PFO) based light emitting diodes by the transient electroluminescence (EL) method. The EL pulses can be divided into the following six regions: (a) a delay region; (b) a fast initial rising edge; (c) a second slower rising edge; (d) a quasisteady state; (e) a fast falling edge; and (f) a slow decay region. The effect of the external magnetic field on the different regions can be obtained by measuring the EL pulses both with and without a magnetic field. It is found that the external magnetic field has no effect on both the electron and hole mobility in PFO based light-emitting diodes when the driving voltage is above the onset of the electroluminescence.