Influence of the Emission Layer Thickness on the Optoelectronic Properties of Solution Processed Organic Light-Emitting Diodes

We investigated the optoelectronic properties of solution processed organic light emitting diodes (OLEDs) as a function of their active layer thickness. By using a horizontal dipping technique and by accelerating the coating bar during wet film deposition, we fabricated OLED arrays with different emission layer thicknesses but identical process records in a single process step. The comparison of the optoelectronic device parameters allows for conclusions on injection limitation, the optimization of the layer thickness, and, in conjunction with optical simulations of the weak cavity effect, to promote a deeper understanding of the emission profile. To show the universality of this method, we investigated purely polymeric emitters, blends of polymers and small molecules as well as all-small molecule material systems.