Anilino-carbazole-based D–π–D′–π–D blue light material coordinated exciplex for achieving white light dynamic regulation

Abstract

An exciplex white light system that can simplify the structure of a device has become an important driving force for the industrialization of white organic light-emitting devices (WOLEDs). Two D–π–D′–π–D-type blue light materials, CzPAF-DPA and CzPAF-DF, based on a core aniline-based carbazole and 9,9-dibutylfluorene as a π bridge with two peripheral donors with varying degrees of conjugation were successfully synthesized by Buchwald–Hartwig amination. Both materials emit blue light and are thermally stable, with thermal decomposition temperatures (T_d) of 408 and 418 °C, respectively. The electroluminescence (EL) spectra of both CzPAF-DPA and CzPAF-DF represented broad-band emission with two primary emission peaks. The shorter-wavelength peaks located at 424/428 nm correspond to the intrinsic emission peak of blue light materials, while the longer-wavelength peaks at 496/500 nm are ascribed to an exciplex generated at the interface between the light-emitting layer and the electron transport layer (ETL). By adjusting the thickness of the light-emitting layer, CzPAF-DPA, a controllable transition from warm white light to cold white light emission was achieved in single-molecule devices fabricated by both vacuum evaporation deposition and wet spin-coating. This research provides a crucial theoretical basis for developing blue light devices compatible with multi-process techniques, and promoting a method for the practical application of OLEDs in printed displays.