AIE-active mechanochromic materials based N-phenylcarbazol-substituted tetraarylethene for OLED applications

Abstract

Multifunctional optoelectronic materials are important in both theoretical and practical aspects. In this study, three luminogens based on N-phenylcarbazol-substituted tetraarylethene, namely, NPCE, MeNPCE and MeONPCE, were designed and synthesised via Friedel–Crafts acylation and the McMurry coupling reaction. All of the luminogens show typical aggregation-induced emission (AIE) characteristics with high solid-state efficiencies of up to 83%. The dyes also exhibit excellent thermal stability (T_d of up to 434 °C) and prominent morphological stability. In addition, only MeONPCE reveals obvious mechanochromism (emission wavelength change of up to 64 nm). This proved that by introducing a methoxy group into one of the phenyl rings at the para position, mechanochromic materials can be easily obtained. The organic light-emitting diodes (OLEDs) that use these dyes as the nondoped emission layer emit cyan light with current efficiency and external quantum efficiency of 7.87 cd A⁻¹ and 3.87%, respectively. In comparison, the multilayer organic light-emitting diodes adopting MeONPCE as the nondoped emission layer reveal that MeONPCE is an eximious p-type light emitter.