Charge carriers and triplets in OLED devices studied by Electrically Detected magnetic resonance

Organic Light-Emitting Diodes (OLEDs) were investigated with an Electron Paramagnetic Resonance (EPR) technique that uses the effective device conductance as the detection channel. This technique enables its to identify and study charge carriers and triplet excitons with high sensitivity. Using a series of model devices, we demonstrate that this type of spectroscopy provides information about triplet energy tran. fer and the location of the recombination zone. The fundamental understanding about the extent of the recombination zone in various OLED architectures helps its to design devices with improved performance.