Synergistic Enhancement of Nondoped OLED Efficiency with EQE ≈15% in Donor‐π‐Acceptor Based Blue Emitters Featuring Combined AIE‐HLCT Characteristics

Abstract Organic light‐emitting diodes (OLEDs) employing hybridized local and charge‐transfer (HLCT) state emitters have exhibited commendable external quantum efficiencies (EQE). However, these emitters typically suffer from reduced photoluminescence quantum yields (PLQYs) in their aggregated states, which diminishes device efficiency. In this work, by introducing an aggregation‐induced emission (AIE) active moiety tetraphenylethene (TPE) and a phenyl spacer to the HLCT‐typed core, phenanthroimidazole (PI) unit, four fluorophores with different substituents at the N1‐position (PI‐Ph‐ p ‐CH 3 ‐TPE, PI‐Ph‐TB‐TPE, PI‐Ph‐ m ‐CF 3 ‐TPE, and PI‐Ph‐ m ‐CN‐TPE) are obtained. The high PLQYs of these HLCT‐AIEgens in aggregates are ensured by their AIE properties. The effects of a phenyl spacer between PI and TPE and different substituents at the N1‐position of PI on the regulation of the locally excited and charge transfer components are also revealed. Theoretical calculations indicate that their exciton conversion channels can be promoted by tuning the excited state, validated by enhancement of their EQE. The non‐doped OLED using PI‐Ph‐ m ‐CF 3 ‐TPE, as an emitter, exhibit the best electroluminescence performance with an excellent EQE approaching 15%, maximum luminance of 4584 cd m −2 , current efficiency of 15.75 cd A −1 , and power efficiency of 13.02 lm W −1 . Strategically designing HLCT‐AIE materials and tuning excited states, high‐efficiency OLED emitters can be developed.