Creation of Bifunctional Materials: Improve Electron-Transporting Ability of Light Emitters Based on AIE-Active 2,3,4,5-Tetraphenylsiloles

Abstract

2,3,4,5-Tetraphenylsiloles are excellent solid-state light emitters featured aggregation-induced emission (AIE) characteristics, but those that can efficiently function as both light-emitting and electron-transporting layers in one organic light-emitting diode (OLED) are much rare. To address this issue, herein, three tailored n-type light emitters comprised of 2,3,4,5-tetraphenylsilole and dimesitylboryl functional groups are designed and synthesized. The new siloles are fully characterized by standard spectroscopic and crystallographic methods with satisfactory results. Their thermal stabilities, electronic structures, photophysical properties, electrochemical behaviors and applications in OLEDs are investigated. These new siloles exhibit AIE characteristics with high emission efficiencies in solid films, and possess lower LUMO energy levels than their parents, 2,3,4,5-tetraphenylsiloles. The double-layer OLEDs [ITO/NPB (60 nm)/silole (60 nm)/LiF (1 nm)/Al (100 nm)] fabricated by adopting the new siloles as both light emitter and electron transporter afford excellent performances, with high electroluminescence efficiencies up to 13.9 cd A–1, 4.35% and 11.6 lm W–1, which are increased greatly relative to those attained from the triple-layer devices with an additional electron-transporting layer. These results demonstrate effective access to n-type solid-state emissive materials with practical utility