New multifunctional aggregation-induced emission fluorophores for reversible piezofluorochromic and nondoped sky-blue organic light-emitting diodes

Abstract

In this study, 4,6-diphenyl-1,3,5-triazine as the rotor, was firstly introduced to the construction of AIEgens. By conjugating phenyl-9H-carbazole and 4,6-diphenyl-1,3,5-triazine to the 9 or 10 position of anthracene, three new multifunctional aggregation-induced emission (AIE) fluorophores, 3-(10-(4,6-diphenyl-1,3,5-triazin-2-yl)anthracen-9-yl)-9-phenyl-9H-carbazole (3CzAnTrz) 9-(4-(10-(4,6-diphenyl-1,3,5-triazin-2-yl)anthracen-9-yl)phenyl)-9H-carbazole (pCzAnTrz) and 9-(3-(10-(4,6-diphenyl-1,3,5-triazin-2-yl)anthracen-9-yl)phenyl)-9H-carbazole (mCzAnTrz) were designed and synthesized. The photophysical properties indicated that all three compounds not only exhibited an AIE effect but also showed a reversible piezofluorochromic (PFC) behaviour. The experimental results revealed that the spectral shifts ΔλPFC (ΔλPFC = λrepressed – λannealed) were obviously influenced by the linking position of 9-phenyl-9H-carbazole, and 3CzAnTrz showed largest spectral shifts (ΔλPFC = 66 nm), because of the relatively loose molecular packing, weak intermolecular CH-π interactions and more twisted conformation. When three fluorophores were used as emitter in the nondoped sky-blue devices, these devices showed excellent electroluminescence (EL) performances, realizing the maximum current efficiency (CE), power efficiency (PE) and external quantum efficiency (EQE) values of 13.34 cd A−1, 11.59 lm W−1, 5.44%; 11.19 cd A−1, 9.25 lm W−1, 5.54% and 8.74 cd A−1, 6.44 lm W−1, 4.71% for 3CzAnTrz, pCzAnTrz, and mCzAnTrz, respectively. And these devices exhibit negligible efficiency roll-off even at 10000 cd m−2. These results manifest that the potential advantage of multifunctional AIEgens applicable for piezofluorochromism and nondoped high-performance EL devices.