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Keywords:

  • aggregation;
  • electroluminescence;
  • organic electronics;
  • light-emitting diodes;
  • tetraphenylethenes

Abstract

A facile approach to thermally stable and efficient solid-state emitters is proposed. By hooking up tetraphenylethene (TPE) units through aryl linkers under Suzuki coupling conditions, a series of arylene bis(tetraphenylethene)s (TPE-Ar-TPE Ar=2,5-dimethyl-1,4-phenylene, 2,5-bis(hexyloxyl)-1,4-phenylene, 1,5-naphthylene, and 9,10-anthracenylene) are prepared in satisfactory to high yields (67–96 %). These molecules are nonluminescent when dissolved in solutions but become highly emissive when aggregated in poor solvents or fabricated as thin film in the solid state, displaying a phenomenon of aggregation-induced emission. Fluorescence quantum yields of 100 % were achieved in the amorphous films of the luminogens. The luminogens exhibit mechano-, vapo-, and thermochromism: their emissions can be repeatedly switched between blue and blue-green colors by simple grinding-fuming and grinding-heating cycles owing to the morphological change from a crystalline to an amorphous state and vice versa. These compounds are thermally stable, losing little of their weight at high temperatures of 421–452 °C. All the luminogens are morphological stable with high glass transition temperatures. Multilayer light-emitting diodes with a device configuration of ITO/NPB/dye/TPBi/Alq3/LiF/Al are fabricated, which emit sky-blue electroluminescence with maximum luminance and external quantum efficiency of 7900 cd m−2 and 2.1 %, respectively.