Pure Blue-Light-Emitting Materials: Hyperbranched Ladder-Type Poly(p-phenylene)s Containing Truxene Units

Hyperbranched Conjugated Polymer with Multiple Charge Transfer Enables High-Efficiency Nondoped Red Electroluminescence with Low Driving Voltage

Conjugated polymers featuring thermally activated delayed fluorescence (TADF) attract tremendous attention in both academic and industry communities due to their easy solution processing for fabricating large-area and low-cost high-performance polymer light-emitting diodes (PLEDs). However, current nondoped solution-processed PLEDs frequently encounter significant efficiency roll-offs and unreasonably high operating voltages at high brightness, especially for red-emitting polymers. Herein, we design hyperbranched conjugated polymers (HCPs) with D-A-D type TADF characteristics for high-performance red-emitting PLEDs. Multiple intramolecular charge transfer (ICT) channels induced by quasi-equivalent donors of the TADF core strongly boost the reverse intersystem crossing (RISC) process and singlet excitons radiative transition. Coupling with the efficient energy transfer process generated by structure advantages of HCPs, the strongly electron-withdrawing oxygen atoms located on the TADF cores further accelerate hole transportation from the host chains to the TADF cores. Under a rational regulation of the TADF core ratio, the related nondoped red-emitting device performs an outstanding performance with an EQE_max of 8.39% and exhibits no roll-off while the luminance is less than 100 cd/m² and only 3.3% decrease at 500 cd/m². Simultaneously, the EQE can maintain 7.4% under 1000 cd/m². Furthermore, the corresponding nondoped device exhibits a low turn-on voltage of around 2.5 V and achieves a luminance of 500 cd/m² at 3.5 V and even 1000 cd/m² at 3.9 V. To our knowledge, this is the best performance among all nondoped red PLEDs with high brightness obtained at low operating voltage.

From truxenes to heterotruxenes: playing with heteroatoms and the symmetry of molecules

As a result of the modification of truxene, we can change the electronic structure or create multidimensional materials. Thus, the use of truxenes is very wide.

Hyperbranched Macromolecules: From Synthesis to Applications

Hyperbranched macromolecules (HMs, also called hyperbranched polymers) are highly branched three-dimensional (3D) structures in which all bonds converge to a focal point or core, and which have a multiplicity of reactive chain-ends. This review summarizes major types of synthetic strategies exploited to produce HMs, including the step-growth polycondensation, the self-condensing vinyl polymerization and ring opening polymerization. Compared to linear analogues, the globular and dendritic architectures of HMs endow new characteristics, such as abundant functional groups, intramolecular cavities, low viscosity, and high solubility. After discussing the general concepts, synthesis, and properties, various applications of HMs are also covered. HMs continue being materials for topical interest, and thus this review offers both concise summary for those new to the topic and for those with more experience in the field of HMs.

Efficient synthesis of 5-oxatruxene and the unusual influence of oxygen heteroatom on its physico-chemical properties

5-Oxatruxene presents new quality among the truxenes. It is a promising compound for the new class of optoelectronic materials.

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

Two novel highly fluorescent hyperbranched polybenzobisthiazole amides with a donor⁻acceptor architecture and large Stokes shift were rationally designed and synthesized. The chemical structures of the prepared hyperbranched polymers were characterized using Fourier Transform Infrared Spectroscopy (FTIR) analysis, Hydrogen Nuclear Magnetic Resonance (¹H-NMR) analysis, and Gel Permeation Chromatography (GPC) analysis. These two polymers were soluble in dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and their DMSO and DMF solutions emitted strong green light (517⁻537 nm) with high quantum yields (QYs) and large Stokes shifts. Their relative fluorescence QYs in the DMSO solution were calculated as 77.75% and 81.14% with the Stokes shifts of 137 nm (0.86 eV) and 149 nm (0.92 eV) for HP⁻COOH and HP⁻NH₂, respectively, using quinine sulfate as the standard. In the DMF solution, the QYs of HP⁻COOH and HP⁻NH₂ were calculated as 104.65% and 118.72%, with the Stokes shifts of 128 nm (0.79 eV) and 147 nm (0.87 eV), respectively. Their films mainly emitted strong blue light with the maximum emission wavelengths of 436 nm and 480 nm for HP⁻COOH and HP⁻NH₂, respectively. The Stokes shifts for HP⁻COOH and HP⁻NH₂ films were 131 nm (0.42 eV) and 179 nm (0.86 eV), respectively. They are promising candidates for luminescent solar concentrators and blue light emitting materials.

Towards Monodisperse Star-Shaped Ladder-Type Conjugated Systems: Design, Synthesis, Stabilized Blue Electroluminescence, and Amplified Spontaneous Emission

A novel series of monodisperse star-shaped ladder-type oligo(p-phenylene)s, named as TrL-n (n=1-3), have been explored. Their thermal and electrochemical properties, fluorescence transients, photoluminescence quantum yields, density functional theory calculations, electroluminescence (EL) and amplified spontaneous emission (ASE) properties have been systematically investigated to unravel the molecular design on optoelectronic properties. The resulting materials showed excellent structural perfection, free of chemical defects, and exhibited great thermal stability (T_d : 404-418 °C and T_g : 147-184 °C) and amorphous glassy morphologies. Compared with their corresponding linear counterparts FL-m (m=1-3), TrL-n showed only little bathochromic shifts (5-12 nm) for the absorption maxima λ_max in both solution and films. The star-shaped ladder-type compounds exhibited enhanced optical stability and suppressed low-energy emission. Their EL spectra exhibited excellent stability with increasing the driving voltage from 6 to 12 V. Moreover, superior low ASE thresholds were recorded for TrL-n compared with FL-m. Rather low ASE threshold (29 nJ per pulse or 1.60 μJ cm^-2 ) was recorded for TrL-3, demonstrating their promising potential as excellent gain media. This study provides a novel design concept to develop monodisperse star-shaped ladder-type materials with excellent structural perfection, which are vital for shedding light on exploring robust organic emitters for optoelectronic applications.

Photophysical and photovoltaic properties of truxene-functionalized conjugated polymer–fullerene supramolecular complexes

We report the photophysical and photovoltaic properties of two truxene-functionalized conjugated copolymers (P1 and P2) containing various 2,1,3-benzothiadiazole segments synthesized through Suzuki and Heck coupling reactions, respectively.

Synthesis and chemosensory properties of two-arm truxene-functionalized conjugated polyfluorene containing terpyridine moiety

We report the responsive fluorescence chemosensory phenomena of a truxene-functionalized conjugated polymer (P1) with pendant terminal terpyridine (tpy) groups as receptors for metal ions synthesized via a Suzuki polymerization reaction.

Very fast singlet and triplet energy transfers in a tri-chromophoric porphyrin dyad aided by the truxene platform

A trichromophoric dyad composed of an octa-β-alkyl-palladium(II)porphyrin (donor) and two tri-meso-aryl-zinc(II)porphyrins (acceptors) held by a truxene spacer exhibits very fast rates for triplet energy transfers at 77 (kET(T1) = 1.63 × 108 s-1) and 298 K (kET(T1) = 3.44 × 108 s-1), whereas the corresponding singlet energy transfer rates, kET(S1) = 3.9 × 1010 s-1 (77 K) and kET(S1) = 6.0 × 1010 s-1 (298 K), are also considered fast. The interpretation for these results is that the energy transfer processes proceed via a through bond Dexter mechanism (i.e. double electron exchange) supported by comparison with literature data and evidence for a moderate MO coupling between the donor and acceptor chromophores in the frontier MOs.

Amide-bridged ladder poly(p-phenylene): synthesis by direct arylation and π-stacked assembly

Amide-bridged ladder poly(p-phenylene) was synthesized in two steps, through the polycondensation of aromatic diamines and dicarboxylic acid derivatives followed by palladium-catalyzed intramolecular direct arylation.

Hyperbranched polymers: advances from synthesis to applications

This review summarizes the advances in hyperbranched polymers from the viewpoint of structure, click synthesis and functionalization towards their applications in the last decade.

Synthesis and Physical Properties of Hyperbranched Polymers Containing Twisted Acenes

Novel hyperbranched co-polymers HP1–HP4 with twisted acene units and truxene groups have been synthesised through Suzuki coupling reaction and characterised. Single crystal analyses showed that the model compounds 3 and 5 had twisted structures with torsion angles of 40.73° and 28.65°, respectively. The polymers show blue light emission in organic solvents and thin films, as well as high stability, which might be utilised as potential candidates for organic electronic materials.

Functional hyperbranched polymers with advanced optical, electrical and magnetic properties

This review summarizes the recent progress in functional HBPs and their application in optics, electronics and magnetics, including light-emitting devices, aggregation-induced emission materials, nonlinear optical materials, chemosensors, solar cells, magnetic materials, etc., and provides outlooks for further exploration in the field.

Ruthenium/base-catalyzed ortho-selective C–H arylation of acylarenes with halogenated arylboronates

Ruthenium-catalyzed ortho-selective C–H arylation of acylarenes with halogenated arylboronates was promoted by the catalytic amount of bases and provided desired halogenated biaryls in excellent yields under 0.2–1 mol% ruthenium catalyst loading.

Origin of the temperature dependence of the rate of singlet energy transfer in a three-component truxene-bridged dyads

We report a truxene-based dyad built upon one donor (tri-meso-phenylzinc(II)porphyrin) and two acceptors (octa-β-alkylporphyrin free base) in which the donor exhibits free rotation around a Ctruxene-Cmeso single bond at 298 K in fluid solution but not at 77 K in a glass matrix, whereas the acceptors have very limited motion as they are blocked by β-methyl groups. This case is interesting because all the structural and spectroscopic parameters affecting the rate for singlet energy transfer according to a Förster Resonance Energy Transfer are only weakly temperature dependent, leaving only the Dexter mechanism explaining the larger variation in rate of energy transfers with the temperature hence providing a circumstantial evidence for a dual mechanism (Föster and Dexter) in truxene-based dyads (or polyads) in the S1 excited states.

Dye-terminated, hyperbranched polytruxenes and polytruxene-block-polythiophene multiblock copolymers made in an "AB2 + A" approach

Novel dye-terminated, hyperbranched polytruxenes and polytruxene-block-polythiophene multiblock copolymers have been synthesized in a simple "AB(2) + A" approach. Photoexcitation into the higher energy polytruxene absorption band results in an efficient excitation energy transfer to the peripheral dye or polythiophene blocks.