Effect of Emitter Position on Emission Intensity in an Organic Planar Microcavity

We have fabricated a λ/2-length planar microcavity between two silver mirrors that had the same thickness and consisted of sandwich structure LiF1/Alq₃/LiF2. By altering the relative thickness of the two LiF layers, the adjustment of the position of thin layer Alq₃ in the microcavity was achieved and the apparent photoluminescence (PL) intensity change was observed. The maximal emission intensity device, corresponding to the luminescence layer located at antinode, is four times of the minimal one whose luminescence layer is near a silver mirror that is close to a node. This indicates that the coupling between vacuum electric-field and dipole strongly affects the emission intensity into the forward direction of the microcavity plane. Compared the PL intensity between the microcavity device and the non-cavity one with the same sandwich structure LiF1/Alq₃/LiF2 in free space, at the resonance wavelength a maximal enhancement factor of nine is obtained.