Polarity tuning of fluorene derivatives by chromophores to achieve efficient blue electroluminescent materials

Abstract

Abstract Highly efficient deep-blue organic light-emitting diode is indispensable to fabricate energy efficient high quality displays and solid-state lightings. In this report, we report a series of fluorene-based emitters, which exhibit tunable polarity dependent on the choice of chromophore. The absorption and emission spectra of the compounds are highly dependent on the nature of chromophore and its contribution to the conjugation or donor-acceptor interaction. The solvatochromism of the dyes in the fluorescence is indicative of the realization of polar excited state, which is dependent on the donor strength of chromophore. Similarly, the oxidation potentials of the dyes are reminiscent of the electron-richness of the chromophores. The dyes are thermally robust comparable to the prominent electroluminescent materials and possess thermal decomposition temperatures greater than 340 °C which increases with the conjugation. The OLED device containing an emitter derived from triphenylamine showed a maximum power efficiency of 5.6 lm/W, maximum external quantum efficiency of 4.2%, and maximum luminance of 4150 cd/m2 with Commission Internationale de l’Eclairage (CIE) coordinates of (0.15, 0.11). The work demonstrates the use of simple chromophores to achieve efficient electroluminescent materials.