Diboron complexes with bis-spiro structures as high-performance blue emitters for OLEDs

Abstract

To construct high-performance organoboron-based blue emitters for electroluminescent (EL) devices, two diboron complexes have been synthesized through the chelation of 2-(1-phenyl-1H-benzo[d]imidazole-2-yl)phenol or 2-(2-pyridyl)phenol ligands with both boron atoms of the 9,10-diboraanthracene group. These complexes exhibit bright blue emissions in solution and in solid films with fluorescence quantum yields over 0.42, which benefit from their bis-spiro structures. In addition, they possess high thermal decomposition (>410 °C) and glass transition (>163 °C) temperatures. Moreover, they are excellent ambipolar transporting materials with high and balanced mobilities (>10⁻⁴ cm² V⁻¹ s⁻¹) for holes and electrons. Due to these excellent properties, the EL devices adopting these complexes as non-doped emitting layers emit blue light and exhibit low turn-on voltages (<3.2 V), high luminance (up to 9041 cd m⁻²), as well as high current (up to 7.01 cd A⁻¹) and power efficiencies (up to 7.58 lm W⁻¹). To the best of our knowledge, these devices are so far the brightest and most efficient blue devices based on four-coordinate organoboron emitters.