Boron, sulfur-doped polycyclic aromatic hydrocarbon emitters with multiple-resonance-dominated lowest excited states for efficient narrowband deep-blue emission

Recent progress and prospects of fluorescent materials based on narrow emission

“…4d). 39 Unfortunately, DFT calculations showed that BSS-Ac is an emitter with distinct ICT characteristics, BSS-SpAc exhibits ICT and MR characteristics, and BSS-PA and BSS-Cz are MR-TADF molecules. Thus, BSS-Ac and BSS-SpAc show dual emission bands, a narrow emission band at 456 nm and a broad emission band at 513 and 505 nm, respectively.…”

Narrowband emission: organic thermally-activated delayed fluorescence materials and underlying mechanisms

“…More recently, Wang and coworkers have proposed four novel B/S-doped emitters, namely BSS-Ac , BSS-SpAc , BSS-PA , and BSS-Cz , consisting of BSS skeletons and various arylamine units with different electron-donating abilities in the para -position as peripheral substituents. 69 These strong donors (Ac and SpAc) have been observed to induce ICT-dominated S 1 states that enable BSS-Ac and BSS-SpAc to exhibit red-shifted emissions (456/513 and 456/505 nm) and broad spectral FWHMs (105 and 101 nm, respectively), compared with those of the parent BSS at 457 nm with a spectral FWHM of 27 nm. In sharp contrast, MR-dominated S 1 states are maintained with the incorporation of a weak donor, such as PA and Cz units, resulting in the desired narrow spectral of 22 nm for BSS-PA and 23 nm for BSS-Cz in toluene.…”

Rational Molecular Design Strategy for High-Efficiency Ultrapure Blue TADF Emitters: Symmetrical and Rigid Sulfur-Bridged Boron-Based Acceptors

“…In our previous work, we found that oxygen/sulfur-bridged cyclized boron-based emitters exhibit a narrow intramolecular charge-transfer (ICT) blue emission and fast reverse intersystem crossing (RISC) process . The sulfur atom can lock the structure to increase molecular rigidity and sever as a heavy atom to promote the RISC process in TADF molecules. − With these considerations in mind, sulfur atoms are introduced into the TAB acceptor structure to make this new structure appropriate as an acceptor for blue TADF emitters with narrowband EL. On the one hand, the rigid and symmetrical molecular structure can inhibit vibrational relaxation, which raises the Franck–Condon factor and results in the high photoluminescence quantum yield (PLQY) with a narrowband emission.…”