Boron‐ and nitrogen‐embedded blue multi‐resonance emitters with low triplet energy

Abstract

AbstractB,N‐doped multi‐resonance (MR) thermally activated delayed fluorescence (TADF) emitters are of significant interest for realizing the high efficiency and remarkable color purity of optoelectronic devices. Due to their moderate singlet‐triplet energy gap, managing triplet state (T1) energy is important to enhance the performance of these devices. Herein, polycyclic aromatic hydrocarbons (PAHs), such as pyrene and anthracene, are appended to the t‐DABNA structure, resulting in t‐DABNA‐PAH compounds, namely t‐DABNA‐pyr and t‐DABNA‐ant. Both compounds display sky‐blue fluorescence which lacks TADF characteristics while preserving high photoluminescence quantum yield (PLQY) and high color purity. The compounds possess low T1 energy (~2.0 eV), which is advantageous for suppressing the accumulation of undesirable long‐lived T1 excitons. Particularly, t‐DABNA‐pyr exhibits emissions with a narrow full width at half maximum (~33 nm) and a high PLQY (~100%) in both solution and rigid states. Theoretical studies further suggest that the low‐energy T1 state is localized at the PAH moiety.