Increased Electromer Formation and Charge Trapping in Solution-Processed versus Vacuum-Deposited Small Molecule Host Materials of Organic Light-Emitting Devices.

We investigate and compare between organic light-emitting devices (OLEDs) fabricated by solution-coating versus vacuum-deposition. Electroluminescence, photoluminescence, and chromatographic measurements on typical OLED host materials reveal significant electromer formation in layers fabricated by solution-processing, pointing to stronger intermolecular interactions in these systems. Delayed electroluminescence measurements reveal that solution-processed layers also have increased charge traps. The findings provide insights on the morphological differences between solution-processed and vacuum-deposited materials and shed light on the root causes behind the lower electroluminescence stability of solution-processed OLEDs.