J. Staudigel et al., A quantitative numerical model of multilayer vapor-deposited organic lightemitting diodes, J APPL PHYS, 86(7), 1999, pp. 3895-3910
A one-dimensional numerical model for the quantitative simulation of multil
ayer organic light emitting diodes (OLEDs) is presented. It encompasses bip
olar charge carrier drift with field-dependent mobilities and space charge
effects, charge carrier diffusion, trapping, bulk and interface recombinati
on, singlet exciton diffusion and quenching effects. Using field-dependent
mobility data measured on unipolar single layer devices, reported energetic
levels of highest occupied and lowest unoccupied molecular orbitals, and r
ealistic assumptions for experimentally not direct accessible parameters, c
urrent density and luminance of state-of-the-art undoped vapor-deposited tw
o- and three-layer OLEDs with maximum luminance exceeding 10000 cd/m(2) wer
e successfully simulated over 4 orders of magnitude. For an adequate descri
ption of these multilayer OLEDs with energetic barriers at interfaces betwe
en two adjacent organic layers, the model also includes a simple theory of
charge carrier barrier crossing and recombination at organic-organic interf
aces. The discrete nature of amorphous molecular organic solids is reflecte
d in the model by a spatial discretization according to actual molecule mon
olayers, with hopping processes for charge carrier and energy transport bet
ween neighboring monolayers. (C) 1999 American Institute of Physics. [S0021
-8979(99)02218-5].