Multifunctional aggregation-induced emission materials for nondoped OLEDs

Organic light-emitting diodes (OLEDs) have attracted considerable attention due to their potential applications in flat-panel displays and solid-state lighting. The active organic materials are very important for fabricating efficient OLEDs. However, many conventional luminescent materials often encounter severe emission quenching in the aggregated state. In addition, these luminescent materials generally can only function as light-emitting layers and require complicated OLED configurations, such as multilayer doped devices. These drawbacks undermine the electroluminescence efficiencies of OLEDs, and raise the manufacturing cost. Luminogens with aggregation-induced emission (AIE) characteristics can emit strongly in the aggregated state, which are ideal light-emitting materials for OLEDs without needing doping technique. This review introduces a series of multifunctional light-emitting materials for OLEDs created by introducing hole-transporting (e.g. carbazole and triphenylamine) or electron-transporting (e.g. dimesitylboryl and benzimidazole) groups to the building blocks with AIE characteristics (e.g. silole and tetraphenylethene). These novel luminescent materials exhibit excellent solid-state emission efficiencies and good carrier-transporting ability. They can not only serve as light-emitting layers, but also simultaneously function as carrier-transporting layers, which display multifunctional characetristics in OLED devices. The highest external quantum efficiencies of bilayer nondoped OLED devices using these materials can exceed the theory limit, which indicates that they can improve efficiencies of OLED devices and simplify the device structures distinctly. Multifunctional materials with AIE properties pave a new way towards reducing the cost of OLED devices. © 2016, Science Press. All right reserved.