Intramolecular exciplex featuring a bis-sp3 C-locked acceptor–donor–acceptor sandwich

Abstract

Intramolecular exciplex systems featuring thermally activated delayed fluorescence (TADF) have garnered significant attention in the realm of organic light-emitting diodes (OLEDs). Nonetheless, the occurrence of organic sandwich intramolecular exciplexes remains rare due to structural limitations and synthetic challenges. Herein, we present a novel rigid acceptor–donor–acceptor (A–D–A) sandwich complex, dSFQP, characterized by two sp³ C-locking moieties. This compound exhibits TADF characteristics facilitated by a multiple through-space charge-transfer process. X-ray crystallographic analysis confirms the distinctive sandwich configuration. The parallel spatial arrangement and minimized A–D–A configuration enhance electronic interactions, resulting in a high photoluminescence quantum yield, rapid reverse intersystem crossing rate, and sluggish nonradiative decay rate. OLEDs employing dSFQP as the dopant achieve a maximum external quantum efficiency (EQE) of 28.5% with a low efficiency roll-off of merely 2.8% at 1000 cd m⁻². Even at a high brightness of 10 000 cd m⁻², the EQE remains notably high at 17.5%. Our current results provide an effective way to further innovate the design of new organic charge-transfer complexes.