Carbazolylphenyl ethynyl anthracenes as TTA emitters with improved horizontal alignment for the applications in OLEDs and for optical detection of the nitroaromatic explosive compounds

Abstract

Synthesis and properties of the carbazolylphenyl ethynyl anthracenes with tert-butyl, methoxy, and methoxyethoxy groups are reported. The compounds exhibit remarkably high thermal stability with the temperatures of the onsets of thermal degradation exceeding 407 °C. The ionization potentials of the compounds range from 5.38 to 5.65 eV. Hole mobilities of the derivatives exceed 1 × 10⁻⁴ cm² × V⁻¹s⁻¹ at high electric fields. The photoluminescence quantum yields of the toluene solutions of the compounds are in the range of 86–97 %. The low-lying triplet excited states with the energy of 1.98 eV are detected experimentally and confirmed by the theoretical calculations utilizing density-functional theory for all the studied compounds. The long-lived photoluminescence with a lifetime of up to 0.19 ms is detected for the film of tert-butylcarbazole-based emitter. Triplet-triplet annihilation as an emissive mechanism of the emitters was discussed. The solid samples of dimethoxycarbazolyl-containing derivative shows photoluminescence quantum yield of 36 %. The triplet–triplet fusion is manifested by the long-lived electroluminescence of organic light emitting diode (OLED) with this compound as the emitter and the slope of 2 of the linear plot of brightness versus current density in log–log scale. The considerable quenching of emission of the dispersions of the compounds in THF/water mixtures with a volume fraction of water of 99 % is observed after the addition of picric acid. The respective Stern-Volmer constants are in the range of 6.3 × 10⁴-1.1 × 10⁵ M⁻¹.