Phenyl-substituted fluorene-dimer cored anthracene derivatives: highly fluorescent and stable materials for high performance organic blue- and white-light-emitting diodes

Abstract

A new series of highly fluorescent blue-emitting materials based on fluorene and anthracene hybrids are designed and synthesized for organic light-emitting diodes (OLEDs). These materials feature a phenyl-substituted fluorene dimer as a bulky and rigid core and anthracene as a functional active group. The novel use of a phenyl-substituted fluorene dimer as building skeleton to design functional molecules is reported for the first time. The thermal, photophysical, electrochemical, and electroluminescent (EL) properties are presented, as well as combined density functional study of their geometry and electronic structure. These compounds show excellent thermal resistance with high glass transition temperature (T_g) in the range 159–257 °C, thermal decomposition temperature (T_d) 441–495 °C, and high fluorescent quantum yield (Φ_F = 0.61–0.96, relative to 9,10-diphenylanthracene) as well as good film-forming and morphological stability. Remarkably, high-performance blue OLEDs are also fabricated in a simple three-layer device architecture using these compounds as emissive layer with luminance efficiency of 2.2–5.1 cd A⁻¹ as a non-doped blue emitter and even higher efficiency of up to 13.6 cd A⁻¹ and maximum external quantum efficiency 4.8% is obtained when doped a blue fluorescent dye, 4,4′-(1E,1′E)-2,2′(biphenyl-4,4′diyl)bis(ethane-2,1-diyl)bis(N,N-dip-tolyaniline) (DPAVBi). Furthermore, we fabricate highly efficient fluorescent white OLEDs employing an interesting emission in the longer wavelength of one of our compound combined with DPAVBi emission to achieve stable white light emission in a binary blend single emissive layer with high efficiency of 14.8 cd A⁻¹ (5.3 lm W⁻¹) and maximum brightness of 50248 cd m⁻².