Controllable Circularly Polarized Electroluminescence Performance Improved by the Dihedral Angle of Chiral-Bridged Binaphthyl-Type Dopant Inducers

Abstract

Chirality of 1,1′-binaphthol (BINOL) is due to the restricted rotation between two naphthalene rings, and its skeletal structure of binaphthyl unit can be further modified by choosing functionalized substituents to afford the enlarged chiral induction effect. In this paper, we designed and synthesized nine chiral binaphthyl derivatives ( R/S-1–R/S-9) as circularly polarized electroluminescence (CP-EL) inducers by inserting various bridged alkyl chains into the hydroxyl groups of BINOL or introducing functionalized substituents with different steric hindrances on the 3,3′-position of 2,2′-methylenedioxy-1,1′-binaphthalene. Their molecular conformations and CPL behaviors of nine chiral inducers were significantly dependent on the length of the alkyl chain and the degree of substituent steric hindrance, which could further regulate their chiral induction effect on achiral fluorescent polymer F8BT from small to large in the doped films. Moreover, in virtue of the planar rigid conjugated molecular conformation of R/S-1, R/S-6, and R/S-9, the amplified CPL signals (|g PL|) were detected as high as 2.36 × 10–2, 2.06 × 10–2, and 1.26 × 10–2 from blends of F8BT and these chiral inducers. The circularly polarized organic light-emitting diode (CP-OLED) device on the blends of F8BT and chiral inducers ( R/S-6) with small dihedron angle and excellent carrier mobility showed a low turn-on voltage (V on < 4.5 V), high brightness (> 10509.6 cd/m2), and maximum |g EL| value of 1.86 × 10–2 (F8BT + 5% R/S-6). This work can develop and provide a valuable reference for CP-OLED device design through chiral dopant induction.

Dynamically stable and amplified circularly polarized excimer emission regulated by solvation of chiral co-assembly process

“…The exchange of (−)-CPEE and (+)-CPEE was closely related to the inversion of excimer chirality caused by the presence or absence of intermolecular hydrogen bonds in the excited state. Our group recently carried out a series of experiments on the amplified CPL emission promoted by the intermolecular chiral transfer of chiral binaphthyl inducers with the anchored dihedral angle 9 , 10 , 40 – 42 . In this paper, we found a dynamically stable and amplified CPEE of an achiral Py-based dye regulated through the solvation effect of chiral co-assembly process.…”

Advances in circularly polarized electroluminescence based on chiral TADF-active materials

“…In addition to cyano-carbazole-type TADF enantiomers, Cheng et al reported a new pair of chiral TADF molecules R / S - BDTPA with BINOL as the chiral perturbed unit, biphenyl boron β-diketonate as an electron acceptor, and biphenylamine as an electron donor in 2021. 22 The obtained chiral boron complexes displayed obvious CPL activities with | g lum | values of 2.2 × 10 −3 and red delayed fluorescence of about 600 nm. Impressively, solution-processed CP-OLEDs with the chiral TADF emitters displayed red CPEL ( λ EL = 600 nm) with | g EL | values of 2.6 × 10 −3 and EQE max of 2.0%.…”

Two Cholesterol-Containing Pyrene Derivatives: Subtle Spacer Difference, Diverse Stimuli-Responsive Luminescence, Chirality, and Self-Assembly Behaviors

“…To realize it, one of the most effective methods is doping chiral luminogens into achiral nematic liquid crystals (N-LCs). − Besides g lum , another important parameter of CPL is the polarization direction (left-handed and right-handed). Inversion of CPL signals was usually realized by changing the molecular structure or chirality of chiral dopants. − It would be more convenient to inverse the CPL signals of N*-LC by simply adjusting the doping ratio of chiral dopants; however, related LC systems were rarely reported.…”