We present a technique to probe the exciton distribution in organic light-emitting diodes. Our method involves strategically inserting sensing layers at different locations in proximity to the emissive zone. In contrast to typical sensing layers that act as a probe of the local exciton density, the sensing layers reported here use long-range energy transfer to probe a large area around the sensing layer. We highlight the importance of material selection, such that exciton distribution could be probed without influencing the electrical and optical properties of the organic light-emitting diodes. We expect that this work will provide an invaluable tool for studying excitons in organic light-emitting diodes.
