Red‐Emitting Fluorophores Featuring Combined Hybridized Local and Charge‐Transfer Excited State and Aggregation‐Induced Emission as Efficient Emitters for Electroluminescent Devices

Abstract

Herein, donor (D)‐acceptor (A) type fluorophores (TTBz and TTNz) were designed and synthesized with different acceptor units. The two acceptor units benzo[c][1,2,5]thiadiazole (Bz) and naphtho[2,3‐c][1,2,5]thiadiazole (Nz) are asymmetrically functionalized with triphenylamine (TPA) as a strong donor and tetraphenylethylene (TPE) as an aggregation‐induced emission (AIE)‐luminogen to realize combined AIE and hybridized local and charge transfer (HCLT) excited state features as well as long‐wavelength emission. Their HCLT and AIE properties are verified by theoretical calculations, solvatochromic effects, and transient photoluminescence decay experiments. They exhibit strong orange‐red and deep‐red fluorescence emission with good thermal stability and hole mobility, leading to effective utilization as emitters in organic light‐emitting diodes (OLEDs). The resulting devices show decent electroluminescent (EL) performance (current efficiency of 12.04–12.58 cd A−1, maximum brightness of 11206–20160 cd m−2, and external quantum efficiency of 5.11–5.47 %). Particularly, the TTNz‐based OLED demonstrates steady deep‐red emission with a peak at 661 nm and CIE coordinates of (0.67, 0.33).