Achieving white-light emission in a single-component polymer with halogen-assisted interaction

White-light emitting(WLE) polymers have attracted continuous attention for their promising applications in solid-state lighting,flexible display and related fields. However, achieving dual-emission and pure white-light emission in a single-component polymer is still challenging. In this study, a brominated single-component polymer Br OD-TFB was designed and synthesized,which shows dual-emission and white light emission properties in solution and room-temperature phosphorescence(RTP) in thin films. The dual-emission properties can be tuned by concentration, solvent polarity, and excitation energy. Spectral analyses and theoretical calculations reveal that the origin of the high-energy emission band(HEB) is intramolecular charge transfer(ICT)along the polymer chain, whilst the low-energy emission band(LEB) originates from the excited-state related to the intra-chain and inter-chain C–Br···π interactions as demonstrated by the single-crystal structure of the model compound. Appropriate control of the formation and the destruction of the halogen-assisted interactions can initiate white-light emission in the singlecomponent polymer. More interestingly, by dispersing Br OD-TFB(0.1 wt%) in a non-emissive, colorless and transparent polymer, the characteristics of this white-light emission can be fully demonstrated while exhibiting unexpected RTP properties,with photoluminescence quantum efficiency(Φ_(PL)) of up to 23% and CIE coordinates of(0.32, 0.32).

Achieving Bright Mechanoluminescence in a Hydrogen-Bonded Organic Framework by Polar Molecular Rotor Incorporation

Luminescent hydrogen-bonded organic frameworks(HOFs)have attracted increasing attention due to their corresponding luminescence that enables readily visualization of structural dynamics.HOFs with the mechanoluminescence(ML)property can emit light without photon excitation and are greatly attractive for advanced applications,but research in this area has been limiting.Herein,we report the first example of an ML-active flexible HOF with permanent porosity,named 8PCOM,assembled from polar molecular rotors with an aggregation-induced emission property.When responding to different solvent vapors,reversible structural transformations between ML-active and-inactive 8PCOM frameworks occur,including a single-crystal-to-single-crystal(SCSC)transformation.Thus,guest-induced breathing behaviors are mainly attributed to phenyl rotations of polar molecular rotors induced by external stimuli.During reversible structural transformations of various 8PCOM frameworks with different pores,the significant ML property is achieved successfully through supramolecular dipole moment regulation.Upon mechanical force,bright emission of the ML-active 8PCOM framework is observed without UV irradiation,and the ML-active crystals can be easily prepared and regenerated.This work not only provides a valuable strategy for engineering future multifunctional HOFs but also enriches the types and applications of existing luminescent porous materials.

Intrinsic persistent room temperature phosphorescence derived from 1H-benzo[f]indole itself as a guest

The influence of 1H-benzo[f]indole(Bd) and its derivatives on room temperature phosphorescence(RTP)has raised great concern since they were found to significantly affect RTP of the extensively studied carbazole(Cz) derivatives. However, the role of Bd itself existing in Cz-based or other doping systems was still unclear. In order to clarify its intrinsic phosphorescent property, Bd was introduced as a guest into different organic matrixes including substituted Cz derivatives and polymers. The phosphorescence located in 560–620 nm was confirmed to be derived from Bd itself, which can be detected whatever Bd was doped in the crystal or amorphous state of Cz derivatives. The suitable energy gap between Cz derivatives and Bd is the key to achieve ultralong RTP of Bd. Additionally, when doped in polymers with plenty of hydrogen bonds, RTP of Bd with lifetime over 280 ms was easily obtained. Among them, Bd@PHEMA(poly(hydroxyethyl methacrylate) exhibited superior phosphorescence, with yellow afterglow lasting for over 2.5 s. Therefore, this work demonstrated that a new organic RTP phosphor, Bd, is discovered, and ultralong RTP of Bd can be achieved not only doped in Cz derivatives but also in polymers as the hosts.

High-efficiency thermally activated delayed fluorescence materials via a shamrock-shaped design strategy to enable OLEDs with external quantum efficiency over 38%

To achieve highly-efficient organic light-emitting diodes(OLEDs),great efforts have been devoted into constructing thermally activated delayed fluorescence(TADF)with high horizontal dipole ratios(Θ//).Here,we proposed a design strategy by integrating a rigid electron-accepting oxygen-bridged boron core with triple electron-donating groups,which exhibited a“shamrock-shape”,namely BO-3DMAC and BO-3DPAC.Benefiting from the rigid and large-planar skeletons brought by shamrock-shaped design,BO-3DMAC and BO-3DPAC exhibit highΘ//of 84%/70%and 93%/94%in neat/doped films,respectively,and finally furnish excellent external quantum efficiencies(EQEs)of up to 28.3%and 38.7%in 20 wt%doped OLEDs with sky-blue emission,as well as adequate EQEs of up to 21.0%and 16.7%in nondoped OLEDs.This work unveils a promising strategy to establish high-Θ//TADF emitters by constructing large-planar molecular structures using shamrock-shaped design.

聚集诱导发光

聚集诱导发光(AIE)是唐本忠院士于2001年提出的一个科学概念,是指一类在溶液中不发光或者发光微弱的分子聚集后发光显著增强的现象。高效固态发光的AIE材料有望从根本上解决有机发光材料面临的聚集导致发光猝灭难题,具有重大的实际应用价值。从分子内旋转受限到分子内运动受限,从聚集诱导发光到聚集体科学,AIE领域已经取得了许多原创性的成果。在本综述中,我们从AIE材料的分类、机理、概念衍生、性能、应用和挑战等方面讨论了AIE领域最近取得的显著进展。希望本综述能激发更多关于分子聚集体的研究,并推动材料、化学和生物医学等学科的进一步交叉融合和更大发展。

Aggregation-induced emission: a coming-of-age ceremony at the age of eighteen

Aggregation-induced emission(AIE) has drawn great attention worldwide for its unique optical phenomenon and huge potential applications. Since coined by Ben Zhong Tang et al. in 2001, AIE has been deeply investigated and widely utilized in many important areas, such as organic light-emitting diode(OLED), sensor, and bio-imaging. Herein, we highlight some important progress of AIE in these eighteen years, including the exploration of internal mechanism and potential applications. Furthermore,some other interestingly emissive behaviors, originating but distinguishing from the AIE concept, are presented. It is anticipated an overall understanding about AIE could be easily caught from this short review for scientists, no matter whether they are involved in this exciting and rising research area or not.

Temperature-Induced Transformation from Large Compound Vesicles to Worm-like Aggregates by ABC Triblock Copolymer

Two triblock polymers, tetraaniline-block-poly（N-isopropyl acrylamide）-block-poly（hydroxyethyl acrylate） （TA-b-PNIPAM-b-PHEA） and TA-b-PHEA-b-PNIPAM, were synthesized with unambiguous structure by a two step method. The difference of these two diblock polymers is the connection order of carboxyl group to block, e.g., carboxyl group to PNIPAM block for PNIPAM-b-PHEA and to PHEA block for PHEA-b-PNIPAM. Secondly, block tetraaniline was linked to the diblock polymer through amidation to yield the corresponding triblock copolymer. Both of them have almost the identical chemical compositions. The only difference is the connection order of each block in the triblock polymers. When they were self-assembled at 45℃ in a suitable solution, both of their aggregates have spherical shape with slight defects on their surface with the average diameter of about 400 nm. However, when their aggregate dispersion was cooled down to 20 ℃, only TA-b-PHEA-b-PNIPAM＇s morphology changed, forming worm-like aggregates with the diameter of about 100-200 nm transformed from spherical ag- gregates. Both amphiphilic property and position of each block in this triblock copolymer are very essential for this morphology transformation. Since the worm-like aggregates presented here by our group have hollow structure in- side, its controlled release properties for doxorubicin were evaluated. Drug release experiment indicated that along with the temperature changes, the rearrangement of the intermediate layer structure caused morphology change in aggregate, thus accelerating the speed of drug release.

Remarkable mechanochromism and force-induced thermally activated delayed fluorescence enhancement from white-light-emitting organic luminogens with aggregation-induced emission

The development of organic materials with white-light emission and thermally activated delayed fluorescence(TADF)properties in the solid state remain a challenge.Herein,a series of white-light-emitting organic luminogens have been developed and are found to show aggregation-induced delayed fluorescence(AIDF)characteristics.The AIDF emitters present dual-emission consisted of prompt fluorescence and TADF in the crystalline state.Their white-light emissions can be easily tuned by altering the chemical structure and connecting position of the heterocyclic aromatic substituent.Under the stimuli of mechanical force and solvent vapor,the compounds exhibit remarkable and reversible mechanochromism,in which their emission colors are switchable between white and yellow.Upon grinding,they also display linearly tunable luminescence colors,as well as force-induced TADF enhancement,which may be associated with the more compact molecular packing and the restriction of intramolecular motions.The results from time-resolved emission scanning and theoretical calculation suggest that the dual-emission of the AIDF luminogens likely results from the twisted intramolecular charge transfer transitions of the molecules,and the reversible mechanochromism properties probably stem from the interconversion of the quasi-axial and the quasi-equatorial conformations.

Sulfonyldibenzene-based hole-transporting materials for efficient n-i-p perovskite solar cells

Organic hole-transporting materials(HTMs)are an essential component in conventional perovskite solar cells(PSCs).In this work,two sulfonyldibenzene-based molecules,named CS-04 and CS-05,are synthesized and employed as HTMs in n-i-p PSCs.In comparison with CS-04,the carbazole-substituted methoxytriphenylamine(Cz MOTPA)group in CS-05 exhibits an increased degree of molecular distortion,thus endowing CS-05 with excellent solvent solubility and film-formation ability.Moreover,CS-05 shows a high hole mobility,superior hole extraction and hole transporting properties.As a result,CS-05 yields impressive device performances with a high power conversion efficiency(PCE)of 20.15%,while that of CS-04 based device is 19.50%,which is comparable to that of the Spiro-OMe TAD based control device(19.59%).This finding illustrates the potential of sulfonyldibenzene-based molecules for the applications in PSCs,and also provides a novel avenue to improve the performances and stability of PSCs by tailoring the sulfonyldibenzene-based molecules.

Hybridized Local and Charge-Transfer Excited-State Fluorophores through the Regulation of the Donor-Acceptor Torsional Angle for Highly Efficient Organic Light-Emitting Diodes

Hybridized local and charge-transfer(HLCT)excitedstate fluorophores,which enable full exciton utilization through a reverse intersystem crossing fromhigh-lying triplet states to singlet state,have attracted increasing attention toward organic light-emitting diodes(OLEDs)application.Herein,we report three D-π-A-π-D-type isomers o-2CzBT,m-2CzBT,and p-2CzBT by adjusting the donor(D)units from ortho-,meta-,to para-substituted positions with the acceptor(A)core unit,respectively.The HLCT properties of the three compounds are evidently confirmed by theoretical calculations,solvatochromic behaviors,and transient decay lifetimes analyses.As the substituted position changes from the ortho-,meta-,and para-positions,the reduced steric hindrance brings about decreased torsional angle between D and A moieties,resulting in increased oscillator strength.Accordingly,the parasubstituted p-2CzBT is endowed with a more locally excited component that accounts for faster radiative decay,leading to a higher fluorescent efficiency than that of o-2CzBT and m-2CzBT.As expected,p-2CzBT enables its nondoped and doped OLEDs with higher external quantum efficiencies(EQEs)of 12.3% and 15.0%,respectively,which are among the state-ofthe-art efficiencies of HLCT-based OLEDs.Moreover,o-2CzBT and m-2CzBT are also utilized as host materials for high-performance OLEDs,thus extending the application of HLCT materials.