High-Performance Organic Electroluminescence: Design from Organic Light-Emitting Materials to Devices

Biodegradable and Ultra-High Expansion Ratio PPC-P Foams Achieved by Microcellular Foaming Using CO2 as Blowing Agent

Poly(propylene carbonate-co-phthalate) (PPC-P) is an amorphous copolymer of aliphatic polycarbonate and aromatic polyester; it possesses good biodegradability, superior mechanical performances, high thermal properties, and excellent affinity with CO2. Hence, we fabricate PPC-P foams in an autoclave by using subcritical CO2 as a physical blowing agent. Both saturation pressure and foaming temperature affect the foaming behaviors of PPC-P, including CO2 adsorption and desorption performance, foaming ratio, cell size, porosity, cell density, and nucleation density, which are investigated in this research. Moreover, the low-cost PPC-P/nano-CaCO3 and PPC-P/starch composites are prepared and foamed using the same procedure. The obtained PPC-P-based foams show ultra-high expansion ratio and refined microcellular structures simultaneously. Besides, nano-CaCO3 can effectively improve PPC-P's rheological properties and foamability. In addition, the introduction of starch into PPC-P can lead to a large number of open cells. Beyond all doubt, this work can certainly provide both a kind of new biodegradable PPC-P-based foam materials and an economic methodology to make biodegradable plastic foams. These foams are potentially applicable in the packaging, transportation, and food industry.

Enhancing Emission and Stability in Na-Doped Cs3Cu2I5 Nanocrystals

Lead-free Cs3Cu2I5 metal halides have garnered significant attention recently due to their non-toxic properties and deep-blue emission. However, their relatively low photoluminescence quantum efficiency and poor stability have limited their applications. In this work, sodium iodide (NaI) is used to facilitate the synthesis of Cs3Cu2I5 nanocrystals (NCs), demonstrating improved photoluminescence intensity, photoluminescence quantum yield, and stability. Systematic optoelectronic characterizations confirm that Na+ is successfully incorporated into the Cs3Cu2I5 lattice without altering its crystal structure. The improved Photoluminescence Quantum Yield (PLQY) and stability are attributed to the strengthened chemical bonding, which effectively suppresses vacancy defects in the lattice. Additionally, light-emitting diodes (LEDs) based on 10% NaI-doped Cs3Cu2I5 NCs were assembled, emitting vibrant blue light with a maximum radiant intensity of 82 lux and Commission Internationale de l'Eclairage (CIE) chromaticity coordinates of (0.15, 0.1). This work opens new possibilities for commercial lighting display applications.

Synthesis, Photophysical Properties and Self-Assembly of a Tetraphenylethylene-Naphthalene Diimide Donor-Acceptor Molecule

The development of new π-conjugated molecular structures with controlled self-assembly and distinct photophysical properties is crucial for advancing applications in optoelectronics and biomaterials. This study introduces the synthesis and detailed self-assembly analysis of tetraphenylethylene (TPE) functionalized naphthalene diimide (NDI), a novel donor-acceptor molecular structure referred to as TPE-NDI. The investigation specifically focuses on elucidating the self-assembly behavior of TPE-NDI in mixed solvents of varying polarities, namely chloroform: methylcyclohexane (CHCl3 : MCH) and chloroform: methanol (CHCl3 : MeOH). Employing a several analytical methodologies, including UV-Vis absorption and fluorescence emission spectroscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD), and dynamic light scattering (DLS), these self-assembled systems have been comprehensively examined. The results reveal that TPE-NDI manifests as distinct particles in CHCl3 : MCH (fMCH =90 %), while transitioning to flower-like assemblies in CHCl3 : MeOH (fMeOH =90 %). This finding underscores the critical role of solvent polarity in dictating the morphological characteristics of TPE-NDI self-assembled aggregates. Furthermore, the study proposes a molecular packing mechanism, based on SEM data, offering significant insights into the design and development of functional supramolecular systems. Such advancements in understanding the molecular self-assembly new π-conjugated molecular structures are anticipated to pave the way for novel applications in material science and nanotechnology.

Synthesis of Pyridin-1(2H)-ylacrylates and the Effects of Different Functional Groups on Their Fluorescence

While fluorescent organic materials have many potential as well as proven applications and so have attracted significant attention, pyridine-olefin conjugates remain a less studied subset of such systems. Herein, therefore, we report on the development of the straightforward syntheses of pyridin-1(2H)-ylacrylates and the outcomes of a study of the effects of substituents on their fluorescent properties. Such compounds were prepared using a simple, metal-free and three-component coupling reaction involving 2-aminopyridines, sulfonyl azides and propiolates. The fluorescent properties of the ensuing products are significantly affected by the positions of substituents on the cyclic framework, with those located in central positions having the greatest impact. Electron-withdrawing groups tend to induce blue shifts while electron-donating ones cause red shifts. This work highlights the capacity that the micro-modification of fluorescent materials provides for fine-tuning their properties such that they may be usefully applied to, for example, the study of luminescent materials.

Aggregation Modes of Chiral Diketopyrrolo[3,4-c]pyrrole Dyes in Solution and Thin Films

The chiroptical features of chiral diketopyrrolo[3,4-c]pyrrole (DPP) derivatives have been only marginally investigated to date. In this regard, we have synthesized ad hoc four chiral DPP dyes, functionalized with enantiopure alkyl groups from natural sources either on the lactam moieties or on the terminal positions of the π-conjugated backbone, to promote an efficient self-assembly into chiral supramolecular structures. For each of them, the aggregation modes has been investigated by absorbance and ECD spectroscopies in conditions of solution aggregation and on thin films, considering the effects of deposition technique (drop casting vs. spin coating) and post-deposition operations (solvent and thermal annealing). The effect of the structure of lateral π-conjugated units attached to the central DPP scaffold, as well as that of the position of the alkyl chiral group, has been assessed. ECD revealed superior capability, compared to absorbance spectroscopy, to provide information on the aggregation modes and to detect the possible co-existence of multiple aggregation pathways.

Luminescence-enhanced conjugated polymer dots through thermal treatment for cell imaging

Conjugated polymer dots (Pdots) are often used as excellent fluorescent probes in the biomedical field. In the process of preparing Pdots, the rapid change of the solvent polarity will result in a messy and defective stacking of the polymer chains in the particle, and these stacking defects of the polymer chains may weaken its luminescence properties. Here, we try to optimize the stacking of the conjugated polymer chains by the thermal annealing treatment. After the low temperature thermal treatment, the fluorescence intensity of Pdots can be enhanced by about 11%-29%, and Pdots maintain their original stability and biosafety. We used transmission electron microscopy (TEM) and single particle fluorescence imaging to reveal the possible mechanism of the chain stacking optimization process, that is, the thermal annealing process of Pdots is the competition between internal chain rearrangement in the particle and particle aggregation. The luminescence-enhanced Pdots exhibit good cellular imaging performance. These results prove that it is feasible to extend the thermal annealing treatment from planar polymer devices to polymer nanoparticles. It provides the possibility to realize stable and complex biological imaging applications using Pdots with a simple molecular structure, and a mature improvement scheme for the mass preparation of Pdots.

Novel carbazole- and dioxino[2,3-b]pyrazine-based bipolar hosts for red PhOLEDs with a high brightness

The target compounds offer new synthetic ideas for red bipolar host materials.

Corrigendum to "Carbonized cotton fiber supported flexible organic lithium ion battery cathodes" [J. Colloid Interface Sci. 572 (2020) 1-8]

Carbonized cotton fibers (CCFs) were prepared by the carbonization of commercial cottons at 700, 800 and 900 °C. The following characterizations indicated that the properties of the obtained CCFs could be effectively tuned by the carbonization temperatures. Containing both high conductivity and high aspect ratio, the CCFs could be used as the conductive agents for the construction of the integrated organic cathodes in lithium ion batteries (LIBs). With the optimized ratio of CCF from 900 °C, the organic LIB cathodes showed a high specific capacity of 135 mA h g^-1 at a current density of 0.05 A g^-1 and an impressive cyclizing stability by keeping 90.5% of the highest capacity value after 500 cycles at 0.5 A g^-1. The moderate mechanical stability of the CCF supported organic cathode enabled the further fabrication of flexible LIBs, which manifested stable performances at various bent states, confirming the potentials of CCFs in flexible energy storage devices.

Carbonized cotton fiber supported flexible organic lithium ion battery cathodes

Carbonized cotton fibers (CCFs) were prepared by the carbonization of commercial cottons at 700, 800 and 900 °C. The following characterizations indicated that the properties of the obtained CCFs could be effectively tuned by the carbonization temperatures. Containing both high conductivity and high aspect ratio, the CCFs could be used as the conductive agents for the construction of the integrated organic cathodes in lithium ion batteries (LIBs). With the optimized ratio of CCF from 900 °C, the organic LIB cathodes showed a high specific capacity of 135 mA h g^-1 at a current density of 0.05 A g^-1 and an impressive cyclizing stability by keeping 90.5% of the highest capacity value after 500 cycles at 0.5 A g^-1. The good mechanical stability of the CCF supported organic cathode enabled the further fabrication of flexible LIBs, which manifested stable performances at various bent states, confirming the potentials of CCFs in flexible energy storage devices.

Conductive polyurethane elastomer electrolyte (PUEE) materials for anodic bonding

Polyurethane elastomer electrolyte (PUEE) represents a promising class of polymer solid electrolytes for the preparation and packaging of flexible devices by anodic bonding. In this work, PUEEs were designed and prepared via a pre-polymerization method and cured at room temperature using polypropylene glycol (PPG), toluene-2,4-diisocyanate (TDI) and 1,4-butanediol (BDO) in the presence of varying amounts of lithium bis(trifluoromethanesulphonyl)imide (LiTFSI). All PUEEs exhibited high thermal stability and conductivity, with the highest ionic conductivity of 9.6 × 10⁻⁵ S cm⁻¹ for PUEE6 (n_{[NHCOO]/Li⁺} = 1) at 55 °C. The results showed that LiTFSI was dissolved completely in the polyurethane matrix, and the complexing reactions occurred between the lithium ions and the polar groups of polyurethane. After that, the prepared PUEE and the Al sheet were successfully joined by the anodic bonding process. The microstructures of the bonded interface between PUEE and the Al sheet with a clear intermediate bonding layer could be observed in the cross-section scanning electron microscopy (SEM) images, and the elements in each layer were also detected by energy dispersive spectroscopy (EDS), which indicated that the PUEE and the Al sheet were bonded together. The maximum tensile strength for bonded PUEE6/Al was up to 0.45 MPa. All these results demonstrated that the prepared PUEE material would be a promising candidate for the preparation and packaging of flexible devices by anodic bonding.

Polyurethane elastomer electrolytes (PUEE) were prepared as flexible substrates to be joined with Al sheets by anodic bonding for the preparation and packaging of flexible devices.

Low-temperature direct synthesis of perovskite nanocrystals in water and their application in light-emitting diodes

Cesium lead halide perovskite nanocrystals (PNCs) have aroused tremendous research attention because of their excellent optoelectronic properties. Herein, we developed a facile and green low-temperature strategy free of organic solvents, in which only pure water was adopted as the solvent, to synthesize CsPbBr3 NCs. Intriguingly, although formed with the assistance of water, the obtained CsPbBr3 NCs present a cubic crystal structure, photoluminescence quantum yield (PLQY) of 75%, and narrow emission line width for bright green emission. Furthermore, both electroluminescence (EL) and photoluminescence (PL)-based light-emitting diodes (LEDs) present intrinsic green emission originating from the as-prepared CsPbBr3 NCs. Hence, this work offered a novel eco-friendly avenue for the preparation of perovskite NCs for their practical applications in LEDs.

Two novel aromatic hydrocarbons: facile synthesis, photophysical properties and applications in deep-blue electroluminescence

Two efficient novel fluorescent naphthalene and fluorene-based aromatic hydrocarbon isomers (1 and 2) are prepared and investigated for organic electroluminescence. These compounds show bright violet to deep-blue emission, narrow full width at half maximum (52 nm), and high photoluminescence efficiency (e.g. 0.61 in CH₂Cl₂, 0.67 in film). Alternation of substituent position on the naphthalene moiety can give rise to remarkable emission variation. The relatively large torsion angle between naphthalene and fluorene suppresses the π–π interactions by weakening the intermolecular interactions in the solid state, which can result in highly efficient fluorescence. Moreover, the 1931 Commission Internationale de L'Eclairage coordinates and maximum emission peak for deep-blue electroluminescence based on 1 are (0.16, 0.08) and 410 nm, respectively.

Novel solution processable aromatic hydrocarbons have been designed and synthesized for deep-blue OLEDs with a maximum emission peak of 410 nm and CIE coordinates of (0.16, 0.08).

Effect of the triptycene scaffold on the photophysical, electrochemical and electroluminescence properties of the iridium(iii) complex

Complex 2 achieves obviously higher nondoped device performance (12.6 cd A⁻¹, 5.5%) than that of complex 1 (9.8 cd A⁻¹, 3.8%).

Polymorphous Luminescent Materials Based on 'T'-Shaped Molecules Bearing 4,7-Diphenylbenzo[c][1,2,5]thiadiazole Skeletons: Effect of Substituents on the Photophysical Properties

Polymorphism, the intrinsic character of one chemical compound with at least two distinct phase arrangements, plays a very key role in the photophysical properties. In this contribution, four 'T'-shaped molecules bearing the 2,1,3-benzothiadiazole (BTD) skeleton, named 5 a-5 d, were prepared and characterized. All compounds exhibited excellent thermal stability and polymorphism in the solid state, evident from thermogravimetric analysis, differential scanning calorimetry, and polarized optical microscopy results. Intense emissions with high photoluminescent quantum yields were achieved both in solution (56-97 %) and neat films (33-98 %). All compounds possessed clearly pH-dependent luminescence properties in solution. Additionally, compound 5 d showed useful mechanochromic luminescence owing to the transformation between the crystal and amorphous state. Employing compounds 5 a-5 d as the dopant, solution-processable organic light-emitting diodes (OLEDs) were fabricated and presented a highest external quantum efficiency of 6.15 %, which is higher than the theoretical value of fluorescence-based OLEDs (∼5 %). This research provided a novel strategy for designing high-efficiency BTD-based polymorphic luminescent materials.

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

In this work, a series of hyperbranched copolymers with fluorene-alt-carbazole as the branches, three-dimensional-structured spiro[3.3]heptane-2,6-dispirofluorene (SDF) as the core, and iridium 1-(4-bromophenyl)-isoquinoline (acetylacetone) (Ir(Brpiq)2acac) as the dimming group were synthesized by one-pot Suzuki polycondensation for white emission. All copolymers show great thermal stabilities and high hole-transporting ability due to the introduction of the carbazole unit. The hyperbranched structures for copolymers can suppress the interchain interactions efficiently, and help to form amorphous films. The fabricated polymer light-emitting devices (PLEDs) based on the above synthesized copolymers realize good white light emission, and achieve high electroluminescence (EL) performance. For example, for the optimized PLED, the maximum luminance and current efficiency reach 6210 cd m-2 and 6.30 cd A-1, respectively, indicating the synthesized hyperbranched copolymers have potential application in solution-processable white polymer light-emitting diodes.

Enhancing singlet oxygen generation in semiconducting polymer nanoparticles through fluorescence resonance energy transfer for tumor treatment

Photosensitizers (PSs) are of particular importance for efficient photodynamic therapy (PDT). Challenges for PSs simultaneously possessing strong light-absorbing ability, high 1O2 generation by effective intersystem crossing from the singlet to the triplet state, good water-solubility and excellent photostability still exist. Reported here are a new kind of dual-emissive semiconducting polymer nanoparticles (SPNs) containing fluorescent BODIPY derivatives and near-infrared (NIR) phosphorescent iridium(iii) complexes. In the SPNs, the BODIPY units serve as the energy donors in the fluorescence resonance energy transfer (FRET) process for enhancing the light absorption of the SPNs. The NIR emissive iridium(iii) complexes are chosen as the energy acceptors and efficient photosensitizers. The ionized semiconducting polymers can easily self-assemble to form hydrophilic nanoparticles and homogeneously disperse in aqueous solution. Meanwhile, the conjugated backbone of SPNs provides effective shielding for the two luminophores from photobleaching. Thus, an excellent overall performance of the SPN-based PSs has been realized and the high 1O2 yield (0.97) resulting from the synergistic effect of BODIPY units and iridium(iii) complexes through the FRET process is among the best reported for PSs. In addition, owing to the phosphorescence quenching of iridium(iii) complexes caused by 3O2, the SPNs can also be utilized for O2 mapping in vitro and in vivo, which assists in the evaluation of the PDT process and provides important instructions in early-stage cancer diagnosis.

The application of a non-doped composite hole transport layer of [MoO3/CBP] n with multi-periodic structure for high power efficiency organic light-emitting diodes

A non-doped multi-periodic structure of composite hole transport layer of [MoO3/CBP] n was applied to organic light-emitting diodes. All devices with such hole transport layers showed low turn-on voltage of about 3 V, ultra-high luminance of >110 000 cd m-2, high current efficiency of >50 cd A-1, and high EQE of more than 15%. The optimized device exhibited power efficiency increase of 66% and 18% relative to the single periodic and doped structure OLEDs. The achievement of the reduced driving voltage and improved power efficiency can be attributed to the significantly enhanced hole injection and transport induced by the multi-periodic structure of composite hole transport layer, which was demonstrated via a series of hole-only devices. For improved hole injection and transport mechanism, we also provided a detailed discussion in combination with atomic force microscopy measurements.

Lysosome-specific sensing and imaging of pH variations in vitro and in vivo utilizing a near-infrared boron complex

A NIR lysosome-targeting boron complex has been developed based on hemicyanine for monitoring pH variations in vitro and in vivo.

A simple and green synthesis of carbon quantum dots from coke for white light-emitting devices

Coke is a by-product of coal. This paper reports a simple and green chemical oxidation method for carbon quantum dots (CQDs) from coke for use in novel applications. The CQDs emit blue fluorescence and have a fluorescence quantum yield of 9.2% and blue-green-red spectral composition of 48%. A light-emitting diode (LED) was fabricated by combining the CQDs as a white-light converter with an ultraviolet chip. The Commission Internationale de L'Eclairage chromaticity coordinate (0.31, 0.35) and correlated color temperature (5125 K) of the LED are located in a cool white light zone, suggesting that they have superior potential application in lighting devices.

CQDs are prepared from coke. The coke-based CQDs as a converter are applied to the white light illumination field.