Simulation of OLED device using a Quantum Model for Emission Spectrum

organicex08.in : Simulation of OLED device using a Quantum Model for Emission Spectrum

Requires: Blaze/Organic Display/Quantum
Minimum Versions: Atlas 5.22.1.R

In this example we simulate a 3-layer device with Alq3/Alq3:DCJTB/NPB similar to that described in [1]

Photon emission model:

We use the Holstein model for the Alq3 and DCJTB spectra in both the electron transport and the emissive layers. The model is parameterized by the exciton-phonon coupling and the exciton hopping energies. The former is set to 1.61 for Alq3. This value was taken from [2].

For DCJTB this number is not available from experiments. We used a slightly higher number than Alq3 since we expect excitons to be localized on DCJTB.

The homogeneous and inhomogeneous broadenings were derived by fitting to experimental data in [2] for Alq3 and then similar broadenings were used for DCJTB.

The additional Stokes shift due to reorganization energy was also used as an additional parameter to properly align the emission and absorption spectra with experiment [2].

Photon Propagation model:

We use the transfer matrix method to propagate the light from emissive layers to the outside. Emission is modeled as Hertzian dipoles placed uniformly across the thickness of the layer, and added incoherently. We observe a strong modification of spontaneous emission lifetime of the dipole due to the presence of interfaces and metal electrode. This is plotted as the average Purcell factor, which is produced by weighing the Purcell factors of each dipole according to the amount of light it emits in free space.

The strong modification of spontaneous emission lifetime must also be fed back into the drift diffusion model. At present, ATLAS is not capable of doing this.

Modification of spontaneous emission lifetime is higher in ETL layer than in EML layer due to the vicinity of ETL to metal electrode.

[1] C.C. Lee et. al. "Electrical and Optical Simulation of Organic Light-emitting devices with fluorescent dopant in the emitting layer" Journal of Applied Physics vol 101, 114501 (2007) [2] Martin Brinkmann, Gregory Gadret, Michele Muccini, Carlo Taliani Correlation between Molecular Packing and Optical Properties in Different Crystalline Polymorphs and Amorphous Thin Films of mer -Tris ( 8-hydroxyquinoline ) aluminum ( III ) Journal of American Chemical Society 122 p. 5147-5157 (2000)

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