Polymeric OLED¶

Create Materials¶

Polymer¶

In this tutorial, we will consider a SY-PPV PLED. We start by generating a new material for the polymer. We will use the Fluorescent Dye template.

We set a HOMO level of -5.4 eV and a LUMO level of -2.8 eV. For the polymer, we will disable the energy level broadening by selecting a delta function. For the excitons, we use a singlet binding energy of 1.3 eV and a triplet binding energy of 1.6 eV. A delta function is again used to disable energy level broadening.

An enhanced singlet-triplet generation ratio of 0.4 will be used. The singlet radiative decay rate is set at \(10^{8}\,\textrm{s}^{-1}\). The non-radiative decay rate is set at \(5\cdot{}10^{7}\,\textrm{s}^{-1}\).

To describe the preferential carrier hopping along the conjugate backbone, anisotropic hopping rates can be specified in the Advanced tab of the materials editor.

We chose here to set an inter-chain prefactor of 0.1 to suppress charge hopping between the chains.

Create Compositions¶

In order to include the morphology of the polymer network, we will create an advanced composition.

In the composition editor, we add fractions for both SY-PPV and the vacuum. We set the vacuum as the background material.

We use the polymer generator to create a polymeric morphology. This generator will attempt to fill the layer using polymeric chains obtained through a self-avoiding walk.

A polymer fraction is specified to determine the portion of the grid that will be filled with the polymeric material. The maximum size of the individual chains is set using the chain length parameter. Note that not every polymer will be able to reach the maximum chain length, either due to confinement by neighboring chains or the finite size of the layer.

The behavior of the self-avoiding walker is set using an anisotropic growth vector, which describes the relative probability that chains grow in any given direction. The rigidity parameter restricts the polymer chain from folding back onto itself within a set number of backbone units.

For SY-PPV, we will use a polymer fraction of 0.8, a chain length of 100 and a backbone rigidity of 4. The chain growth probability towards the electrodes will be doubled in order to generate a directed conductor.

Create a Stack¶

We will create a stack containing 2 layers. The electron transfer is assumed to proceed through a metallic layer.

• Add a 20 nm layer of PEDOT:PSS

• Add a 60 nm layer of the polymer composition

We will enable the default Förster interactions for this stack, removing the processes that involve the vacuum.

Create a Parameter Set¶

We will use the Single Voltage Point template to create a parameter set. The voltage is set to 5 V.

Because the polymer layer contains voids, we have to manually set the electrode energy levels. We use an energy of -4.8 eV for the anode and -3.0 for the cathode.

Starting the Simulation¶

We start a new simulation using the voltage point parameter set.

We select 5 disorder instances to improve the sampling of the polymer network.

Simulation Output¶

The morphology of the polymer layer can be viewed in the Morphology section of the Box Report.