Revealing weak spin-orbit coupling effects on charge carriers in a π -conjugated polymer

Spin-orbit coupling (SOC) effects on charge carriers in organic light emitting diodes (OLEDs) impact spin lifetimes, spin-transport properties, and magnetic-field effects. Previous attempts to measure SOC in organic semiconductors have been indirect. Here, the authors utilize quantum chemistry to predict the effect of SOC on magnetic resonance line shapes as determined by the microscopic -tensor. To test the predictions, they measure electrically detected magnetic resonance on OLEDs at high fields of up to 12T. The results indicate that the structural disorder of the polymer has only weak influence on SOC and that spin-related phenomena in OLEDs are fundamentally monomolecular in nature.