Photonic Structure Induced Enhancement in the Triplet State Dynamics of Organic Phosphors at Room Temperature

Triplet state modification in organic phosphorescence molecules for a desired color and quantum yield is typically pursued by chemical modification. A facile methodology is introduced to tune the triplet state dynamics of a phosphorescent molecule by changing the host-matrix parameters. An organic phosphor, Br2PmDI (2–Bromo pyromellitic diimide), dispersed at dilute levels (1.5 wt.%) in a semicrystalline high-κ relaxer ferroelectric host matrix emit room-temperature phosphorescence accompanied by a delayed fluorescence component. The host relaxer ferroelectric polymer film can be engineered to form a photonic matrix with a regular micropore structure of refractive index contrast ≈0.6 that can increase the density of optical states and introduce photonic coupling. The phosphorescence quantum yield of Br2PmDI in this photonic matrix increases by ≈2.3 fold, and the lifetime reduces by a factor of three. The coupled quantum states are investigated by time-resolved spectroscopy at different temperatures and pump intensities.