Propeller-shape isomers with turn-on through-space charge transfer for solution-processed non-doped organic light-emitting diodes

Abstract

Purely organic thermally activated delayed fluorescence (TADF) emitters have developed rapidly in the last decade. Recently, the TADF materials with through-space charge transfer (TSCT) attract great attention due to the ease of tuning the optoelectronic properties for organic light-emitting diodes (OLEDs). Herein, we report the design and synthesis of three propeller-shape emitters via isomer engineering, which are named as TRZ-o-SDMAC, TRZ-m-SDMAC and TRZ-p-SDMAC respectively. Surprisingly, TRZ-o-SDMAC and TRZ-m-SDMAC simultaneously exhibit TADF and aggregation-induced emission. In contrast, the para-linked emitter TRZ-p-SDMAC exhibited no delayed fluorescence with only the nanosecond-scale (12 ns) transient decay. The solution-processed non-doped TADF-OLEDs based on the meta-linked compound TRZ-m-SDMAC render a maximum external quantum efficiency of 20.3 %, which is substantially high than those of the ortho- and para-linked analogues. This work manifests the unique feature of turn-on TSCT and thus TADF via isomeric strategy.