Deep-Red Fluorophore Based on Naphthothiadiazole as Emitter with HLCT, AIE and Ambipolar Transporting Properties for Electroluminescent Device

Abstract

Herein, we report the synthesis and characterization of an efficient ambipolar charge-carrier-transporting deep-red fluorophore (TPECNz) based on donor-acceptor-donor (D-A-D) type molecule and its application as a non-doped emitter in an organic light-emitting diode (OLED). TPECNz contains naphtho[2,3-c][1,2,5]thiadiazole (Nz) as a strong acceptor unit symmetrically functionalized with N-(4-(1,2,2-triphenylvinyl)phenyl)-carbazole as a donor and aggregation-induced emission (AIE) luminogen. The experimental (solvatochromic and emission in THF-water mixture studies) and theoretical investigations prove that TPECNz retains cooperative hybridized local and charge transfer (HLCT) and AIE features. Thanks to its D-A-D type structure with a proper twist angle between D and A units, a strong electron deficiency of Nz unit, and electron donating and hole-transporting natures of carbazole, TPECNz exhibits a strong deep red emission (lem = 648 nm) with a high fluorescence quantum yield of 96%, outstanding thermal property (Tg = 236 oC), and ambipolar charge-carrier-transporting property with a decent balance of mobility of electron (1.50 x 10-5 cm2 V-1 s-1) and hole (4.42 x 10-6 cm2 V-1 s-1). TPECNz is successfully employed as a non-doped emitter in OLED which displays deep red electroluminescent emission peaked at 659 nm with CIE coordinates of (0.664, 0.335)), an EQEmax of 3.32% and exciton utilization efficiency (EUE) of 47%.