R. Osterbacka et al., ELECTRIC-FIELD REDISTRIBUTION AND ELECTROLUMINESCENCE RESPONSE-TIME IN POLYMERIC LIGHT-EMITTING-DIODES, Journal of applied physics, 84(6), 1998, pp. 3359-3363
The electric field redistribution due to injected and trapped charge c
arriers in Langmuir-Blodgett (LB) films of poly(3-hexylthiophene) (P3H
T) sandwiched between indium tin oxide and aluminum (Al) electrodes as
function of applied voltage has been studied using charge collection
measurements by the time-of-flight technique. For mu tau E<d (the drif
t distance shorter than the interelectrode distance) the amount of the
collected photocharge is a function of electric field near the Al ele
ctrode and has been used to probe the time evolution of it. The respon
se time for the field to redistribute inside the P3HT LB film was foun
d to be of the order of 5-200 mu s, in good agreement with the delay t
ime observed in time-resolved electroluminescence measurements in ligh
t-emitting diodes (LED) of similar LB films. We suggest a model for th
e response times in organic LEDs based on these results. (C) 1998 Amer
ican Institute of Physics.