Publication details for Professor Michael PettyPearson, C, Cadd, D H, Petty, M C & Hua, Y L (2009). Effect of dye concentrations in blended-layer white organic light-emitting devices based on phosphorescent dyes. Journal of Applied Physics 106(6): Article 064516.
- Publication type: Journal Article
- ISSN/ISBN: 0021-8979, 1089-7550
- DOI: 10.1063/1.3226780
- Keywords: Dyes, Electrical conductivity, Electroluminescence, Electron traps, Excitons, Organic light emitting diodes, Phosphorescence, Polymer blends, Space-charge-limited conduction.
- Further publication details on publisher web site
- Durham Research Online (DRO) - may include full text
Author(s) from Durham
The electronic and optoelectronic behavior of white organic
light-emitting devices (OLEDs) based on blue (FIrpic) and red
[Ir(piq)(2)(acac)] phosphorescent dyes doped into the same layer of a
polyvinylcarbazole (PVK) host are reported. The conductivity of all the
OLEDs studied appeared to be dominated by space-charge injection
effects, exhibiting a current I versus voltage V dependence of the form
I alpha V-n, with n approximate to 7 at applied voltages at which
electroluminescence was observed. Systematic studies of the current
versus voltage and light-emitting behavior of the OLEDs have identified
different excitation processes for the two dyes. It is suggested that
electroluminescence from the FIrpic molecules originates by direct
transfer of the exciton energy from the PVK to the dye molecules, while
the process of light emission from the Ir(piq)(2)(acac) molecules
involves carrier trapping. The efficiency of the devices can be tuned,
to some extent, by varying the thickness of the organic film. Luminous
efficiencies and luminous power efficiencies of 8 cd A(-1) and 3 lm W-1
were measured for these blended-layer OLEDs, with Commission
Internationale de l'Eclairage coordinates of 0.35, 0.35.
Other keywords: Electron transporting material, P-Phenylene-vinylene, Limited conduction, Diodes, Efficiency, Polymer, State, Degradation, Complexes, Lifetime.