Imaging the microscopic variation in spin properties of organic light emitting diodes

Abstract

Spin is a quantum property fundamental to the charge-light conversion process in optoelectronic devices. Organic materials offer unique opportunities to exploit spin due to their long coherence and lifetimes. The hyperfine interaction, which dominates the spin-dependent recombination processes of these materials, can be chemically tuned on a molecular level while retaining the large-scale fabrication techniques of those materials. To date, this property has been treated monolithically, characterized by a single value across a device. We utilize optical microscopy to spatially resolve the magnetoluminescence effect of an OLED and show the intra-device variation of this spin property reaches nearly 30%. We explore how the variation of this property changes with the operating bias to probe the underlying spin physics and show that these molecular-scale interactions are spatially correlated microscopically over the device.