Electrical control of photon spin angular momentum in organic electroluminescent materials

The photon spin information encoded in circularly polarised (CP) light is of high interest for current and future technologies, including low power displays, encrypted communications and high performance quantum applications. Engineering organic light-emitting diodes (LED) to emit opposite handed electroluminescent CP light typically requires access to left- and right-handed chiral molecules. In conjugated polymer LEDs, the handedness of CP electroluminescence (EL) also depends on the active layer thickness or direction of current flow. For a given active layer thickness, it has remained unknown whether a single-handed chiral material can emit opposite handedness CP light in the same LED architecture – until now. Here we demonstrate organic LEDs where the handedness of the emitted CP EL can be controlled electrically, solely through the use of interlayers with no change in the emissive material composition or thickness. We reveal that this occurs due to a change in mechanism for the generation of CP EL, as a function of the recombination zone position within the device. This result provides a paradigm shift in the realisation of organic CP-LEDs with controllable spin angular momentum information and further contributes to ongoing discussions relating the fundamental physics of chiral optoelectronics.