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

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).