Abstract
The doping effect on charge carrier mobility in tris (8-hydroxyquinolinato) aluminum(Alq3) was studied by time-of-flight (TOF) measurements. The polar dopant, 4-(dicyanomethylene)-2-methyl-6-(p-dimethylaminostyryl)-4H-pyran (DCM) was used forthis study. The DCM doped into Alq3 films reduced the electron mobility. The electricfielddependence electron mobility in Alq3:DCM films was separated into two discreteregions of critical field . The value of was ranged from 360 to 405 (V/cm)1/2 depending on DCM doping concentration up to 24 wt.% in Alq3 films. The energeticdisorder in Alq3:DCM films was increased from 0.01 eV to 0.09 eV with DCM dopingconcentration in Alq3. The positional disorder in Alq3:DCM films was increased from 0.3to 6.5 with DCM doping concentration up to 24 wt.%. These results indicated very strongCoulombic and dipole-dipole interactions between DCM and Alq3 molecules. The codopedof rubrene with DCM into Alq3 improved the carrier mobility compared to thesingle doped Alq3:DCM film. The carrier mobility in single doped Alq3:rubrene andAlq3:DCM films was not closely followed the Poole-Frenkel (PF) model. The mobilitywas in agreement with the PF model at two different ranges of electric fields separated bya critical field . The mobility in co-doped rubrene and DCM into Alq3 followed thelinear relationship with the PF model. The details of our investigations and themechanism of the dopin effects will be discussed in the presentation.
© 2005 Optical Society of America
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