Influence of the Deposition Rate on the Alignment and Performance of Perylene-3,4,9,10-tetracarboxylic Tetraethyl Ester in an Organic Light Emitting Diode

The structural properties of perylene-3,4,9,10-tetracarboxylic tetraethyl ester as an emitter layer of organic light emitting diodes are investigated by grazing incidence wide-angle X-ray scattering and angular dependent photoluminescence measurements. Comparison of the results with previous X-ray investigations on single crystals of the same compound indicates the coexistence of the columnar phase that is found in single crystals with another columnar phase, which exhibits a slightly larger unit cell. The appearance of the latter phase can be reduced by smaller deposition rates of the organic layer. Consequently, slow evaporation results in a better electroluminescence efficiency.