Modular construction of medium-to-long wavelength multi-resonant fluorescent emitters

Efficient multiple resonance (MR) materials play a crucial role in display applications due to their extremely narrow bandwidth emission and high photoluminescence efficiency (Φ_PL). However, achieving a wide range of color tuning without compromising color purity remains a persistent challenge for MR emitters. This study introduces naphthalene, pyrene, anthracene, and perylene units through a simple modular approach to extend π-conjugation and facilitate wavelength shifts. Four MR fluorescent BNBCZ, BPBCZ, BFBCZ, and BPLBCZ emitters exhibit tunable narrowband emission characteristics from green to red in toluene, with spectra maxima at 509, 532, 559, and 605 nm, with full-width at half maximum values of 26, 29, 32, and 31 nm, respectively. Furthermore, all materials show high Φ_PLs of up to 95%. Notably, with the assistance of a thermally activated delayed fluorescence molecule, the sensitized organic light-emitting diodes based on these materials demonstrate good performances, achieving maximum external quantum efficiencies of 19.5%, 21.4%, 21%, and 23%, respectively, with low efficiency roll-off. The corresponding CIE coordinates of (0.24, 0.68) and (0.65, 0.35) closely align with the International Telecommunication Union's requirements for green and red electroluminescence.