Combinatorial Device Fabrication and Optimization of Multilayer Organic LEDs

In order to get a detailed understanding of organic light-emitting devices (OLEDs), optimize their performance and provide reliable data for device modeling, we have developed an ultra-high vacuum (UHV) evaporation system for combinatorial studies. Our system allows the simultaneous fabrication of 10 x 10 individual devices on one substrate enabling a systematic variation of material combinations and electrodes as well as device parameters such as layer thickness, layer sequence, dye dopant concentrations. Here, we present an overview of the capabilities of combinatorial methods for electrical and electro-optical device optimization. We show results on multilayer OLEDs ranging from the conventional copper--phthalo-cyanine (CuPc)/N,N'-di-(naphtalene-1-yl)--N,N'-diphenyl
-benzidine (NPB) and tris--(8-hydroxy-quinolinato)-aluminum (Alq) trilayer device to double-doped, red-emitting OLEDs with efficiencies up to 1.5 cd/A at 20 mA/cm*2 measured through a semitransparent metal electrode and CIE color coordinates of x=0.65, y=0.34.

Keywords: combinatorial method, organic light-emitting device, organic electroluminescence, multilayer, optimization