Hyperbranched fluorene-alt-carbazole copolymers with spiro[3.3]heptane-2,6-dispirofluorene as the core and their application in white polymer light-emitting devices

Abstract

A series of hyperbranched copolymers with fluorene-alt-carbazole as the branches and three-dimensionalstructured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the core were synthesized by one-pot Suzuki polycondensation. 4,7-Dithienyl-2,1,3-benzothiadiazole (DBT) as the orange-light emitting unit was introduced into the backbones to obtain white-light emission. The thermal, photoluminescent (PL), electrochemical and electroluminescent (EL) properties of the copolymers were investigated. The copolymers show great thermal stabilities by the introduction of a carbazole moiety. Besides, the HOMO energy levels of the copolymers were enhanced and the hole injection was improved because of the hole-transporting ability of the carbazole unit. The hyperbranched structures suppress the interchain interactions efficiently, and help to form amorphous films. The copolymers exhibit efficient EL performance as a result of the hyperbranched structure with the incorporation of the carbazole moiety.A quite low turn-on voltage of 5.3 V, a maximal luminance of 7409.5 cd m À2 and a luminous efficiency of 4.27 cd A À1 were achieved with a CIE coordinate of (0.32, 0.26) for the PFCzSDF10DBT10 (10 mol% of SDF and 0.1 mol% of DBT) device. The hyperbranched framework based on fluorene-alt-carbazole branches and SDF core are attractive candidates for solution-processable white polymer light-emitting device (WPLED) applications. † Electronic supplementary information (ESI) available: 1 H NMR and 13 C NMR characterization of DBrCz and 1 H NMR characterization of the copolymers and PFCzSDF10DBT7. UV-vis absorption of DBT and PL spectra of PFCz in CHCl 3 solution (10 À5 mol L À1 ), and PL spectra of DBT in CHCl 3 solution (10 À5 mol L À1 ). See

Synthesis and properties of hyperbranched polymers for white polymer light-emitting diodes

“…4 and Table 3 . The oxidation potentials ( E ox ) vary slightly from 0.86 to 0.93 V. The HOMO levels of polymers are calculated according to the empirical formulas E HOMO = − ( E ox + 4.5) (eV), 5 they are at about −5.40 eV. The lowest unoccupied molecular orbital (LUMO) levels are deduced from the HOMO levels and the optical band gaps ( E g ) determined from the onset value of the absorption spectrum in film in the long-wavelength direction ( E g = 1240/ λ edge ), and they are at −2.30 eV to −2.38 eV.…”

“…Hyperbranched polymers, as a new type of photoelectric material, have attracted more and more attention. [1][2][3][4][5][6] This kind of material has a three-dimensional molecular structure, which can cause large steric hindrance in the distribution of the polymer chains to restrain the concentration quenching intermolecular interaction. Three-dimensional hyperbranched structures with globular features can impart polymers with specic advantages relative to their linear counterparts, such as enhanced solubility, thermal stability, and luminous efficiency.…”

ON/OFF Spiroconjugation through Peripheral Functionalization: Impact on the Reactivity and Chiroptical Properties of Spirobifluorenes

“…SBFs offer high solubility and spiroconjugation, [16,17] and the 90° arrangement of the two fluorene rings around the spiro carbon leads to a rigid 3D structure and high stability. Given all these features, SBFs have found many applications in organic electronics, [18–20] catalysis, [21] and polymer chemistry [22–24] . The expression of spiroconjugation in SBFs stems from the fully antisymmetric combination (AA) between four p orbitals of the carbon atoms directly attached to the spiro center with respect to the two perpendicular planes (Figure 1).…”

Synthesis of Novel Hyperbranched Polybenzo-Bisthiazole Amide with Donor–Acceptor (D-A) Architecture, High Fluorescent Quantum Yield and Large Stokes Shift

“…Over the past few decades, hyperbranched polymers have drawn continuous and considerable attention because of their unique molecular architecture, improved physical and chemical properties, and their broad range of applications, such as fluorescent probes [ 1 , 2 , 3 , 4 , 5 ], polymer coatings [ 6 , 7 ], Separation materials [ 8 ], drug or biomolecule carrier materials [ 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 ], and in optoelectronic materials and devices [ 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. Compared to linear polymers, hyperbranched polymers have the obvious advantages of high solubility, little chain entanglement, low viscosity, good processability, tunable light emission, low crystallinity, and controllable thin film morphology [ 27 , 28 ].…”