Manipulating photophysical properties through asymmetric modification of triptycene-fused multi-resonance TADF emitter

Developing multi-resonance (MR) effect-induced thermally activated delayed fluorescence (TADF) emitters that exhibit excellent photophysical properties and a sterically shielded structure is crucial for achieving high-efficiency and stable organic light-emitting diodes (OLEDs). Herein, we propose a new synthetic approach to asymmetric bulky MR-TADF emitters based on a B,N core. Three asymmetric Tp-fused MR emitters (1–3) are produced by attaching a bulky and rigid triptycene (Tp) moiety on one side of the MR core and introducing different N-containing functional groups on the other side. All emitters exhibit high photoluminescence quantum yield, narrow full width at half maximum, and TADF properties with reasonable reverse intersystem crossing rates (~10⁴ s⁻¹) in a rigid matrix. Notably, the emission color of the emitters ranges from deep blue to sky blue, depending on the N-containing functional groups. Electrochemical and theoretical studies further demonstrate that the frontier molecular orbitals are distributed over the MR core formed by the two moieties, and the resulting energy levels vary accordingly. The findings of this study will be useful for the design of various color-tunable yet sterically shielded MR-TADF emitters.