  Devices which exploit the quantum properties of materials are widespread,
with quantum information processors and quantum sensors showing significant
progress. Organic devices offer interesting opportunities for quantum
technologies owing to their engineerable spin properties, with spintronic
operation and spin resonance magnetic-field sensing demonstrated in research
grade devices, as well as proven compatibility with large scale fabrication
techniques. Yet several important challenges remain as we move toward scaling
these proof-of-principle quantum devices to larger integrated logic systems or
spatially smaller sensing elements, particularly those associated with the
variation of quantum properties both within and between devices. Here,
spatially resolved magnetoluminescence is used to provide the first
two-dimensional map of a spin property - the Overhauser field - in an organic
light-emitting diode. We find intra-device variabilities exceeding 20% while
spatially correlated behaviour is exhibited on lengths beyond $7 \,
\mathsf{\mu}m$, similar in size to pixels in state-of-the-art AMOLED arrays,
which has implications for the reproducibility and integration of organic
quantum devices.
