Synthesis and Application of Salicylhydrazone Probes with High Selectivity for Rapid Detection of Cu2

Using the aldehyde amine condensation procedure and the triphenylamine group as the skeleton structure, the new triphenylamine-aromatic aldehyde-succinylhydrazone probe molecule DHBYMH was created. A newly created acylhydrazone probe was structurally characterized by mass spectrometry (MS), NMR, and infrared spectroscopy (FTIR). Fluorescence and UV spectroscopy were used to examine DHBYMH's sensing capabilities for metal ions. Notably, DHBYMH achieved a detection limit of 1.62 × 10-7 M by demonstrating exceptional selectivity and sensitivity towards Cu2+ ions in an optimum sample solvent system (DMSO/H2O, (v/v = 7/3); pH = 7.0; cysteine (Cys) concentration: 1 × 10-4 M). NMR titration, high-resolution mass spectrometry analysis, and DFT computation were used to clarify the response mechanism. Ultimately, predicated on DHBYMH's reversible identification of Cu2+ ions in the presence of EDTA, a molecular logic gate was successfully designed.

A triphenylamine-based carbohydrazide hydrazone fluorescent probe for selective detection of hypochlorite and sensing acidic gases

Hypochlorous acid and its hypochlorite are important reactive oxygen species in the body, and are involved in various physiological processes related to immunity; their rapid detection is of great significance. Here, we synthesized a fluorescent probe (TPAS) by condensation of 4-(diphenylamino)benzaldehyde, carbohydrazide, and salicylaldehyde, which can be used for the detection of ClO- in water and sensing of acidic gas in its solid state. The probe showed strong selective recognition of ClO- in acetonitrile and good tolerance to interference ions. There were good linear responses between the intensity of absorbance and fluorescence and the amount of ClO-. The TPAS solid and its paper strips can emit red fluorescence when exposed to volatile acidic vapours. After being treated with NH3, the red fluorescence can be restored to yellow. The response process of TPAS to ClO- and acid gases was characterized using nuclear magnetic resonance, electrospray ionisation mass spectrometry, transmission electron microscopy, and density functional theory calculations. Furthermore, it can be utilized in analyzing ClO- in commercially available bleaching products; the detection results were basically compatible with the labelled values. In addition, the probe is biocompatible and can be applied for imaging ClO- in zebrafish.

Nanoparticles of Push-Pull Triphenylamine-Based Molecules for Light-Controlled Stimulation of Neuronal Activity

Organic semiconductor materials with a unique set of properties are very attractive for interfacing biological objects and can be used for noninvasive therapy or detection of biological signals. Here, we describe the synthesis and investigation of a novel series of organic push-pull conjugated molecules with the star-shaped architecture, consisting of triphenylamine as a branching electron donor core linked through the thiophene π-spacer to electron-withdrawing alkyl-dicyanovinyl groups. The molecules could form stable aqueous dispersions of nanoparticles (NPs) without the addition of any surfactants or amphiphilic polymer matrixes with the average size distribution varying from 40 to 120 nm and absorption spectra very similar to those of human eye retina pigments such as rods and green cones. Variation of the terminal alkyl chain length of the molecules forming NPs from 1 to 12 carbon atoms was found to be an efficient tool to modulate their lipophilic and biological properties. Possibilities of using the NPs as light nanoactuators in biological systems or as artificial pigments for therapy of degenerative retinal diseases were studied both on the model planar bilayer lipid membranes and on the rat cortical neurons. In the planar bilayer system, the photodynamic activity of these NPs led to photoinactivation of ion channels formed by pentadecapeptide gramicidin A. Treatment of rat cortical neurons with the NPs caused depolarization of cell membranes upon light irradiation, which could also be due to the photodynamic activity of the NPs. The results of the work gave more insight into the mechanisms of light-controlled stimulation of neuronal activity and for the first time showed that fine-tuning of the lipophilic affinity of NPs based on organic conjugated molecules is of high importance for creating a bioelectronic interface for biomedical applications.

Near-IR Electrochromic Film with High Optical Contrast and Stability Prepared by Oxidative Electropolymerization of Triphenylamine Modified Terpyridine Platinum(II) Chloride

Terpyridine (TPY) platinum(II) chloride with a triphenylamine (TPA) group was successfully synthesized. The strong intramolecular Donor(TPA)-Acceptor(TPY) interaction induced the low-energy absorption band, mixing the spin-allowed singlet dπ(Pt)→π*(TPY) metal-to-ligand charge transfer (MLCT) with the chloride ligand-to-metal charge transfer (LMCT) and chloride ligand-to-ligand (TPY) charge transfer (LLCT) transitions, to bathochromically shift to λmax = 449 nm with significant enhancement and broadening effects. Using the cyclic voltammetry method, its oxidative electropolymerization (EP) films on working Pt disk and ITO electrodes were produced with tunable thickness and diffusion controlled redox behavior, which were characterized by the SEM, EDS, FT-IR, and AC impedance methods. Upon applying +1.4 V voltage, the sandwich-type electrochromic device (ECD) with ca. 290 nm thickness of the EP film exhibits a distinct color transformation from red (CIE coordinates: L = 50.75, a = 18.58, b = 5.69) to dark blue (CIE coordinates: L = 45.65, a = -1.35, b = -12.49). Good electrochromic (EC) parameters, such as a large optical contrast (ΔT%) of 78%, quick coloration and bleaching response times of 2.9 s and 1.1 s, high coloration and bleaching efficiencies of 278.0 and 390.5 C-1·cm2, and good cycling stability (maintains 70% of the initial ΔT% value after 3200 voltage switching cycles), were obtained.

A Novel Fluorescence Sensor for Iodide Detection Based on the 1,3-Diaryl Pyrazole Unit with AIE and Mechanochromic Fluorescence Behavior

A D-A type of luminophore, TPA-CDP, was designed and synthesized by using triphenylamine (TPA) as D (electron donor), 1,3-diaryl pyrazole with cyano groups (CDP) as A (electron acceptor) and employing a cyanovinyl segment as a recognition group. Firstly, TPA-CDP demonstrates effective fluorescence quenching as a sensor for I- by the nucleophilic addition reaction of the cyanovinyl segment with a high level of sensitivity, selectivity and a low determination limit of 4.43 μM. Interestingly, TPA-CDP exhibited an AIE phenomenon with the fw value reaching 50%. In addition, TPA-CDP displayed distinct mechanochromic fluorescence behavior with 70 nm red shift, which was observed over four repeated cycles. Furthermore, the mechanochromic fluorescence behavior of TPA-CDP, as observed in powder XRD experiments, was found to be associated with the morphological transition from a crystalline state to an amorphous state. These results confirm the significant potential of CDP as a powerful electron-deficient component in the creation of D-A-type mechanochromic fluorescence materials and biosensors for detecting I-.

Triphenylamine-Based Helical Polymer for Flexible Memristors

Flexible nonvolatile memristors have potential applications in wearable devices. In this work, a helical polymer, poly (N, N-diphenylanline isocyanide) (PPIC), was synthesized as the active layer, and flexible electronic devices with an Al/PPIC/ITO architecture were prepared on a polyethylene terephthalate (PET) substrate. The device showed typical nonvolatile rewritable memristor characteristics. The high-molecular-weight helical structure stabilized the active layer under different bending degrees, bending times, and number of bending cycles. The memristor was further employed to simulate the information transmission capability of neural fibers, providing new perspectives for the development of flexible wearable memristors and biomimetic neural synapses. This demonstration highlights the promising possibilities for the advancement of artificial intelligence skin and intelligent flexible robots in the future.

Rational Design of Bifunctional Microporous Organic Polymers Containing Anthracene and Triphenylamine Units for Energy Storage and Biological Applications

In this study, we synthesized two conjugated microporous polymers (CMPs), An-Ph-TPA and An-Ph-Py CMPs, using the Suzuki cross-coupling reaction. These CMPs are organic polymers with p-conjugated skeletons and persistent micro-porosity and contain anthracene (An) moieties linked to triphenylamine (TPA) and pyrene (Py) units. We characterized the chemical structures, porosities, thermal stabilities, and morphologies of the newly synthesized An-CMPs using spectroscopic, microscopic, and N₂ adsorption/desorption isotherm techniques. Our results from thermogravimetric analysis (TGA) showed that the An-Ph-TPA CMP displayed better thermal stability with T_d10 = 467 °C and char yield of 57 wt% compared to the An-Ph-Py CMP with T_d10 = 355 °C and char yield of 54 wt%. Furthermore, we evaluated the electrochemical performance of the An-linked CMPs and found that the An-Ph-TPA CMP had a higher capacitance of 116 F g^-1 and better capacitance stability of 97% over 5000 cycles at 10 A g^-1. In addition, we assessed the biocompatibility and cytotoxicity of An-linked CMPs using the MTT assay and a live/dead cell viability assay and observed that they were non-toxic and biocompatible with high cell viability values after 24 or 48 h of incubation. These findings suggest that the An-based CMPs synthesized in this study have potential applications in electrochemical testing and the biological field.

Triphenylamine-Containing Benzoic Acids: Synthesis, Liquid Crystalline and Redox Properties

The synthesis, characterization and liquid crystalline and electrochemical properties of novel triarylamines, in which the triphenylamine platform is non-symmetrically modified with a 4-(6-oxyhexyloxy)benzoic acid group, are reported. Compounds show columnar liquid crystalline behavior, as confirmed through the use of polarized optical microscopy, differential scanning calorimetry and X-ray diffraction. Electrochemical properties were measured using cyclic voltammperometry, obtaining low oxidation potentials and HOMO values that were optimum for consideration as organic semiconductors in hole transport layers. In addition, the photoredox activity of one of these derivatives in dichloromethane was studied under light irradiation. A photooxidation/assembly process under white light irradiation occurs without the assistance of hydrogen bonding amide functional groups.

Novel Pyrimidine-Based Iridium Complexes with Bulky Charge-Carrier Groups as Dopants for Highly Efficient Green Polymer Light-Emitting Diodes

Two new pyrimidine-based iridium complexes with triphenylamine and tetraphenylsilane, namely (TPAPr)2IrAcac and (TPSPr)2IrAcac, were fully synthesized and characterized. Both of the targeted iridium complexes exhibit excellent thermal stability and high photoluminescence quantum yields. Compared to (TPAPr)2IrAcac, (TPSPr)2IrAcac achieved its highest PLQY and current efficiency (CE) at higher dopant concentration probably because of its bulky tetraphenylsilane group, which can effectively suppress the concentration quenching. However, according to DFT studies, (TPSPr)2IrAcac shows faster non-radiative transitions due to the presence of more excited-state distortions than (TPAPr)2IrAcac. As a result, Green phosphorescent polymer light-emitting diodes (PLEDs) containing (TPAPr)2IrAcac and (TPSPr)2IrAcac as dopants exhibit exceptional device performance with peak CE values of 38.24 cd A-1 and 36.06 cd A-1, respectively. (TPAPr)2IrAcac exhibited a superior efficiency than (TPSPr)2IrAcac because of its high Фp, low RMSD value, and efficient energy transfer from the host to the guest. More importantly, the PLEDs based on (TPAPr)2IrAcac and (TPSPr)2IrAcac show stable phosphorescent emission with Commission Internationale de L'Eclairage (CIE) coordinates of (0.313, 0.497) and (0.299, 0.483), respectively. This work points out a viable method for creating phosphorescent iridium complexes based on pyrimidine for high-efficiency organic light-emitting diodes (OLEDs).

Conjugated Microporous Polymers Based on Ferrocene Units as Highly Efficient Electrodes for Energy Storage

This work describes the facile designing of three conjugated microporous polymers incorporated based on the ferrocene (FC) unit with 1,4-bis(4,6-diamino-s-triazin-2-yl)benzene (PDAT), tris(4-aminophenyl)amine (TPA-NH₂), and tetrakis(4-aminophenyl)ethane (TPE-NH₂) to form PDAT-FC, TPA-FC, and TPE-FC CMPs from Schiff base reaction of 1,1'-diacetylferrocene monomer with these three aryl amines, respectively, for efficient supercapacitor electrodes. PDAT-FC and TPA-FC CMPs samples featured higher surface area values of approximately 502 and 701 m² g^-1, in addition to their possession of both micropores and mesopores. In particular, the TPA-FC CMP electrode achieved more extended discharge time compared with the other two FC CMPs, demonstrating good capacitive performance with a specific capacitance of 129 F g^-1 and capacitance retention value of 96% next 5000 cycles. This feature of TPA-FC CMP is attributed to the presence of redox-active triphenylamine and ferrocene units in its backbone, in addition to a high surface area and good porosity that facilitates the redox process and provides rapid kinetics.

Modulating the G-Quadruplex and Duplex DNA Binding by Controlling the Charge of Fluorescent Molecules

Two fluorescent and non-toxic spirobifluorene molecules bearing either positive (Spiro-NMe3) or negative (Spiro-SO3) charged moieties attached to the same aromatic structure have been investigated as binders for DNA. The novel Spiro-NMe3 containing four alkylammonium substituents interacts with G-quadruplex (G4) DNA structures and shows preference for G4s over duplex by means of FRET melting and fluorescence experiments. The interaction is governed by the charged substituents of the ligands as deduced from the lower binding of the sulfonate analogue (Spiro-SO3). On the contrary, Spiro-SO3 exhibits higher binding affinity to duplex DNA structure than to G4. Both molecules show a moderate quenching of the fluorescence upon DNA binding. The confocal microscopy evaluation shows the internalization of both molecules in HeLa cells and their lysosomal accumulation.

Construction of Porous Organic/Inorganic Hybrid Polymers Based on Polyhedral Oligomeric Silsesquioxane for Energy Storage and Hydrogen Production from Water

In this study, we used effective and one-pot Heck coupling reactions under moderate reaction conditions to construct two new hybrid porous polymers (named OVS-P-TPA and OVS-P-F HPPs) with high yield, based on silsesquioxane cage nanoparticles through the reaction of octavinylsilsesquioxane (OVS) with different brominated pyrene (P-Br₄), triphenylamine (TPA-Br₃), and fluorene (F-Br₂) as co-monomer units. The successful syntheses of both OVS-HPPs were tested using various instruments, such as X-ray photoelectron (XPS), solid-state ¹³C NMR, and Fourier transform infrared spectroscopy (FTIR) analyses. All spectroscopic data confirmed the successful incorporation and linkage of P, TPA, and F units into the POSS cage in order to form porous OVS-HPP materials. In addition, the thermogravimetric analysis (TGA) and N₂ adsorption analyses revealed the thermal stabilities of OVS-P-F HPP (T_d10 = 444 °C; char yield: 79 wt%), with a significant specific surface area of 375 m² g^-1 and a large pore volume of 0.69 cm³ g^-1. According to electrochemical three-electrode performance, the OVS-P-F HPP precursor displayed superior capacitances of 292 F g^-1 with a capacity retention of 99.8% compared to OVS-P-TPA HPP material. Interestingly, the OVS-P-TPA HPP showed a promising HER value of 701.9 µmol g^-1 h^-1, which is more than 12 times higher than that of OVS-P-F HPP (56.6 µmol g^-1 h^-1), based on photocatalytic experimental results.

A simple molecular design towards the conversion of a MCL backbone to a multifunctional emitter exhibiting polymorphism, AIE, TADF and MCL

Compared with the large number of single-function materials such as aggregation-induced emission (AIE), mechanochromic luminescence (MCL), or thermally activated delayed fluorescence (TADF) emitters, multifunctional emitting materials offer more opportunities in practical applications. In this report, we provide a simple molecular design strategy towards the conversion of a MCL building block to a multifunctional emitter. Through altering the substituent sites and increasing the number of electron donors and steric hindrance on a normal MCL backbone benzo[d,e]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one, a novel multifunctional material 10,11-bis-(4-diphenylamino-phenyl)-benzo[d,e]benzo[4,5]imidazo[2,1-a]isoquinolin-7-one (10,11-2TPA-BBI) is designed and synthesized. 10,11-2TPA-BBI exhibits simultaneous polymorphism, AIE, MCL and TADF properties. It can form four different aggregate species: yellow solid (YS) and orange solid (OS), orange flake-shaped crystal (OC), and red prism-like crystal (RC). Among them, because of the small energy gaps (ΔE_STs < 0.3 eV) between the singlet and triplet excited states, OS, OC and RC exhibit TADF properties, while YS show normal fluorescence characteristics with a large ΔE_ST of 0.33 eV. OS can be reversibly transformed into YS upon external stimuli, which can be attributed to the emission switch between local excited state and charge transfer state. Crystallographic study indicates that the bulky structure and weak intermolecular interactions account for polymorphism and AIE properties. This work will provide a simple molecular design strategy for multifunctional materials.

Spectroscopic and Physicochemical Investigations of Azomethines with Triphenylamine Core towards Optoelectronics

Three new azomethines based on triphenylamine with two or three substituents were obtained. Chemical structure and purity were confirmed by ¹H NMR, FTIR elemental analysis and mass spectroscopy. The investigations were focused on the relationship between chemical structure and properties important for optoelectronic materials. Thus, the studies of thermal, optical and electrochemical properties were carried out based on differential scanning calorimetry, thermogravimetric analysis, electronic absorption, photoluminescence and cyclic voltammetry measurements. The ongoing consideration of experimental results was complemented by theoretical calculations using the density functional theory method. The donor activity of obtained compounds was tested in bulk-heterojuntion photovoltaic cells with structure ITO/PEDOT:PSS/imine:PCBM/Al and ITO/PEDOT:PSS/imine:P3HT:PCBM/Al). The effect of the presence of the amino-thiophene-3,4-dicarboxylic acid diethyl ester groups and various number of hexyloxyphenyl units on imines properties was demonstrated.

A Novel Triphenylamine-Based Flavonoid Fluorescent Probe with High Selectivity for Uranyl in Acid and High Water Systems

Developing a fluorescent probe for UO₂²⁺, which is resistant to interference from other ions such as Cu²⁺ and can be applied in acidic and high-water systems, has been a major challenge. In this study, a "turn-off" fluorescent probe for triamine-modified flavonoid derivatives, 2-triphenylamine-3-hydroxy-4H-chromen-4-one (abbreviated to HTPAF), was synthesized. In the solvent system of dimethyl sulfoxide:H₂O (abbreviated to DMSO:H₂O) (v/v = 5:95 pH = 4.5), the HTPAF solution was excited with 364 nm light and showed a strong fluorescence emission peak at 474 nm with a Stokes shift of 110 nm. After the addition of UO₂²⁺, the fluorescence at 474 nm was quenched. More importantly, there was no interference in the presence of metal ions (Pb²⁺, Cd²⁺, Cr³⁺, Fe³⁺, Co²⁺, Th⁴⁺, La³⁺, etc.), especially Cu²⁺ and Al³⁺. It is worth noting that the theoretical model for the binding of UO₂²⁺ to HTPAF was derived by more detailed density functional theory (DFT) calculations in this study, while the coordination mode was further verified using HRMS, FT-IR and ¹HNMR, demonstrating a coordination ratio of 1:2. In addition, the corresponding photo-induced electron transfer (PET) fluorescence quenching mechanism was also proposed.

Quenching singlet oxygen via intersystem crossing for a stable Li-O(2) battery

Aprotic Li-O₂ batteries are a promising energy storage technology, however severe side reactions during cycles lead to their poor rechargeability. Herein, highly reactive singlet oxygen (¹O₂) is revealed to generate in both the discharging and charging processes and is deterimental to battery stability. Electron-rich triphenylamine (TPA) is demonstrated as an effective quencher in the electrolyte to mitigate ¹O₂ and its associated parasitic reactions, which has the tertiary amine and phenyl groups to manifest excellent electrochemical stability and chemical reversibility. It reacts with electrophilic ¹O₂ to form a singlet complex during cycles, and it then quickly transforms to a triplet complex through nonradiative intersystem crossing (ISC). This efficiently accelerates the conversion of ¹O₂ to the ground-state triplet oxygen to eliminate its derived side reactions, and the regeneration of TPA. These enable the Li-O₂ battery with obviously reduced overvoltages and prolonged lifetime for over 310 cycles when coupled with a RuO₂ catalyst. This work highlights the ISC mechanism to quench ¹O₂ in Li-O₂ battery.

Triphenylamine, Carbazole or Tetraphenylethylene-Functionalized Benzothiadiazole Derivatives: Aggregation-Induced Emission (AIE), Solvatochromic and Different Mechanoresponsive Fluorescence Characteristics

The development of mechanochromic fluorophors with high-brightness, solid-state fluorescence is very significant and challenging. Herein, highly solid-state emissive triphenylamine, carbazole and tetraphenylethylene-functionalized benzothiadiazole derivatives were developed. These compounds showed remarkable aggregation-induced emission and solvatochromic fluorescence characteristics. Furthermore, these fluorogenic compounds also displayed different mechanically triggering fluorescence responses.

Highly Crystalline Graphene as the Atomic 2D Blanket of a Perovskite Absorber for Enhanced Photovoltaic Performance

Perovskite solar cells (PSCs) have demonstrated enormous potential for next-generation low-cost photovoltaics. However, due to the intrinsically low bond energy of the perovskite lattice, the long-term stability is normally undermined by ion migration initiated by the electric field and atmospheric conditions. Therefore, ideal ion migration inhibition is important to achieve an enhanced stability of PSCs. Herein, we first introduce a chemical vapor deposition (CVD) fabricated highly crystalline graphene as an atomic 2D blanket directly for the perovskite absorber of PSCs. Iodine and lithium ion migration is effectively inhibited for perovskite solar cells under a continuous static electric field. The water and oxygen corrosion of the unencapsulated device has been dramatically mitigated with atomic graphene blanketing on the perovskite film. With triphenylamine (TPA) molecule modification, the photoconversion efficiencies (PCEs) of the blanketed devices reach 21.54%. The sample with blanket graphene maintains 85% of the initial efficiency, in comparison to 52% of the control sample under voltage bias. After 600 h of aging at 25 °C and 55 RH%, 86% in comparison to <30% of the PCE for the control device is obtained for the sample with a graphene blanket. Thus, we propose that crystalline graphene has an excellent and effective ion-blocking blanket potential for highly stable perovskite devices.

Multivalent Supramolecular Assembly Based on a Triphenylamine Derivative for Near-Infrared Lysosome Targeted Imaging

Near-infrared (NIR) targeted cell imaging has become a research hotspot due to the advantages of deeper tissue penetration, minimal interference from the background signals, and lower light damage. Herein, we report a multivalent supramolecular aggregate with NIR fluorescence emission, which was fabricated from triphenylamine derivatives (TPAs), cucurbit[8]uril (CB[8]), Si-rhodamine (SiR), and hyaluronic acid (HA). Interestingly, possessing a rigid luminescent core and cationic phenylpyridinium units linked by flexible alkyl chains, the tripaddle hexacationic TPA could bind with CB[8] at a 2:3 stoichiometric ratio to form a network-like multivalent assembly with enhanced red luminescence. Such organic two-dimensional network-like aggregate further co-assembled with the energy acceptor SiR and cancer cell targeting agent HA, leading to nanoparticles with NIR emission at 675 nm via an intermolecular energy transfer pathway. Furthermore, the obtained multivalent supramolecular aggregate was successfully applied in lysosome targeted imaging toward A549 cancer cells, which provides a convenient strategy for NIR targeted cell imaging.

High-Performance Electrochromic Covalent Hybrid Framework Membranes via a Facile One-Pot Synthesis

Porous framework materials have sparked enormous interest in the electrochromic field, as they possess intrinsic high porosity and a large surface area that are beneficial for electron and ion transport. However, the fabrication of these porous framework materials often requires multiple processing steps or harsh reaction conditions, which significantly limit large-scale fabrication of such materials. In this work, we report a one-pot in situ polycondensation method to construct electrochromic covalent hybrid framework membranes via nucleophilic substitutions between hexachlorocyclotriphosphazene (HCCP) and triphenylamine (TPA) in an ambient environment. With the high transparency of polyphosphazene in a wide optical range, the constructed phosphazene-triphenylamine (PPTA) covalent hybrid framework membranes can be reversibly switched between light gray and dark blue, with a high transmittance change of up to 79.8%@668 nm and fast switching time (<4 s). Owing to the easy one-pot fabrication and good electrochromic properties, the PPTA covalent hybrid framework membrane has great potential in various fields such as displays and dynamic optical windows.

Investigation of electrochemistry and electrochromic performance of metallopolymer formed by electropolymerization of Fe(II) complex with triphenylamine-hydrazone ligand

The complex of Fe(II) ions of general formula [FeL2](BF4)2 with triphenylamine-hydrazone ligand L has been synthesized and characterized. Oxidative electropolymerization of the complex proceeded smoothly on the working electrode producing homogenous thin film of metallopolymer. The film thickness and morphology of the layer was investigated by microscopy techniques such as SEM and AFM, and the composition of the film was confirmed by XPS analysis. It was found that after fifty successive oxidation/reduction cycles the film of thickness 120 nm was formed on the electrode surface. The metallopolymer was also characterized using cyclic voltammetry and spectroelectrochemical methods. The film was found to change its color from yellow to green-blue, high change in transmittance of 60% at 770 nm and good electrochemical stability during 375 cycles of switching of the potential between -0.1 V and +1.5 V, due to the presence of metal ions that link two ligand molecules resulting in formation of highly cross-linked film. The switching times (coloration and bleaching) were calculated to be 34.2 s and 7.3 s, respectively. Coloration efficiency of the formed film of polymeric complex was found to be 144 cm 2 /C.

Synthesis of Arylene Ether-Type Hyperbranched Poly(triphenylamine) for Lithium Battery Cathodes

We synthesized a new poly(triphenylamine), having a hyperbranched structure, and employed it in lithium-ion batteries as an organic cathode material. Two types of monomers were prepared with hydroxyl groups and nitro leaving groups, activated by a trifluoromethyl substituent, and then polymerized via the nucleophilic aromatic substitution reaction. The reactivity of the monomers differed depending on the number of hydroxyl groups and the A₂B type monomer with one hydroxyl group successfully produced poly(triphenylamine). Based on thermal, optical, and electrochemical analyses, a composite poly(triphenylamine) electrode was made. The electrochemical performance investigations confirmed that the lithium-ion batteries, fabricated with the poly(triphenylamine)-based cathodes, had reasonable specific capacity values and stable cycling performance, suggesting the potential of this hyperbranched polymer in cathode materials for lithium-ion batteries.

Acridine Based Small Molecular Hole Transport Type Materials for Phosphorescent OLED Application

Two small molecular hole-transporting type materials, namely 4-(9,9-dimethylacridin-10(9H)-yl)-N-(4-(9,9-dimethylacridin-10(9H)-yl)phenyl)-N-phenylaniline (TPA-2ACR) and 10,10′-(9-phenyl-9H-carbazole-3,6-diyl)bis(9,9-dimethyl-9,10-dihydroacridine) (PhCAR-2ACR), were designed and synthesized using a single-step Buchwald–Hartwig amination between the dimethyl acridine and triphenylamine or carbazole moieties. Both materials showed high thermal decomposition temperatures of 402 and 422 °C at 5% weight reduction for PhCAR-2ACR and TPA-2ACR, respectively. TPA-2ACR as hole-transporting material exhibited excellent current, power, and external quantum efficiencies of 55.74 cd/A, 29.28 lm/W and 21.59%, respectively. The achieved device efficiencies are much better than that of the referenced similar, 1,1-Bis[(di-4-tolylamino)phenyl]cyclohexane (TAPC)-based device (32.53 cd/A, 18.58 lm/W and 10.6%). Moreover, phenyl carbazole-based PhCAR-2ACR showed good device characteristics when applied for host material in phosphorescent OLEDs.

Effect of the Spatial Configuration of Donors on the Photovoltaic Performance of Double D-π-A Organic Dyes

Three double D-π-A sensitizers (A1, A3, and A5) containing different donors (triphenylamine, methoxy-modified triphenylamine, and cyclic thiourea-functionalized triphenylamine) are synthesized to investigate the role of different donors in dye-sensitized solar cells (DSSCs). Detailed investigations of the sensitizers reveal that the spatial characteristics of donor units have a considerable impact on the light-harvesting, electrochemistry, and photovoltaic properties. Benefiting from the strong shielding ability of alkyl chains in the donor to its branch chains as observed in density functional theory (DFT), the open-circuit voltage (V_OC = 712.0 mV) of A5-based DSSC is higher than those of A1 and A3 by 90 and 78 mV, respectively. Therefore, the A5-based DSSC delivers a good efficiency of 8.54%, relying on its effective suppression of interfacial recombination. The results indicate that the judiciously tailored donor unit is an effective approach to optimize dye configurations to further improve power conversion efficiencies.

Triarylamine-Pyridine-Carbonitriles for Organic Light-Emitting Devices with EQE Nearly 40

Highly efficient thermally activated delayed fluorescence (TADF) molecules are in urgent demand for solid-state lighting and full-color displays. Here, the design and synthesis of three triarylamine-pyridine-carbonitrile-based TADF compounds, TPAPPC, TPAmPPC, and tTPAmPPC, are shown. They exhibit excellent photoluminescence quantum yields of 79-100% with small ΔE_ST values, fast reverse intersystem crossing (RISC), and high horizontal dipole ratios (Θ_//  = 86-88%) in the thin films leading to the enhancement of device light outcoupling. Consequently, a green organic light-emitting diode (OLED) based on TPAmPPC shows a high average external quantum efficiency of 38.8 ± 0.6%, a current efficiency of 130.1 ± 2.1 cd A^-1 , and a power efficiency of 136.3 ± 2.2 lm W^-1 . The highest device efficiency of 39.8% appears to be record-breaking among TADF-based OLEDs to date. In addition, the TPAmPPC-based device shows superior operation lifetime and high-temperature resistance. It is worth noting that the TPA-PPC-based materials have excellent optical properties and the potential for making them strong candidates for TADF practical application.

Bis(Triphenylamine)Benzodifuran Chromophores: Synthesis, Electronic Properties and Application in Organic Light-Emitting Diodes

A series of bis(triphenylamine)benzodifuran chromophores have been synthesized and fully characterised. Starting from suitably functionalized benzodifuran (BDF) precursors, two triphenylamine (TPA) moieties are symmetrically coupled to a central BDF unit either at 4,8-positions through double bonds (1) and single bonds (2) respectively, or at 2,6-positions through double bonds (3). Their electronic absorption and photoluminescence properties as well as redox behaviour have been investigated in detail, indicating that the π-extended conjugation via vinyl linkers in 1 and 3 leads to comparatively strong electronic interactions between the relevant redox moieties TPA and BDF. Due to intriguing electronic properties and structural planarity, 3a has been applied as a dopant emitter in organic light-emitting diodes. A yellowish-green OLED exhibits a high external quantum efficiency (EQE) of 6.2%, thus exceeding the theoretical upper limit most likely due to energy transfer from an interface exciplex to an emissive layer and/or favorable horizontal orientation.

Silsesquioxane-Based Triphenylamine-Linked Fluorescent Porous Polymer for Dyes Adsorption and Nitro-Aromatics Detection

In order to enrich hybrid materials, a novel fluorescent silsesquioxane-based polymer (denoted as PCS-OTS) was synthesized by Friedel-Crafts reaction starting from octavinylsilsesquioxane (OVS) with triphenylamine-functionalized silsesquioxane monomer (denoted as OTS) with AlCl₃ as catalyst. PCS-OTS possessed a high surface area of 816 m²/g and a unique bimodal pore structure. The triphenylamine unit endowed PCS-OTS with excellent luminescence, which made it act as a sensitive chemical sensor and detect p-nitrophenol with high sensitivity (K_SV = 81,230 M^-1). Moreover, PCS-OTS can significantly remove dyes, and the respective adsorption capacity for Rhodamine B (RB), Congo red (CR) and Methyl Orange (MO) is 1935, 1420 and 155 mg/g. Additionally, it could simultaneously remove multiple dyes from water by simple filtration and be easily regenerated. This hybrid porous polymer can be a good choice for water treatment.

Single-Molecule White-Light-Emitting Starburst Donor-Acceptor Triphenylamine Derivatives and Their Application as Ratiometric Luminescent Molecular Thermometers

White-light emission (WLE) from a single molecule is a highly desirable alternative to a complex mixture of complementary colour emitters, which suffers from poor stability and reproducibility for potential use in organic electronic devices and lighting applications. We report single-molecule WLE both in solution and thin films by judiciously controlled π-electron delocalisation between the triarylamine subchromophoric units. Triphenylamine (TPA) forms the central core, and the phenyl rings are substituted with the electron-deficient acceptor 3-ethylrhodanine (Rh) and electron-rich donors triphenylamine or carbazole. The enforced biphenyl configuration of the TPA core and the other donors renders the π-conjugation across the entire chromophore poor, thus the individual subchromophoric units retain their individual emission characteristics, which cover all three primary colour emissions, that is, red, green and blue (RGB). TPA-Rh units exhibit broad fluorescence in the green-red region originating from the local excited (LE) state and intramolecular charge transfer state (ICT), strongly influenced by the solvent, water, and temperature. Different fluorescence parameters, including spectral maxima, ratiometric changes in ICT emission at the expense of blue emission from terminal donor units, and changes in lifetime, have a linear relationship with temperature between 180-330 K, thus the molecules can function as a multiparameter luminescent molecular thermometer. A temperature coefficient of 0.19 K^-1 in ratiometric fluorescence changes along with a spectral shift of 0.3 nm K^-1 and their workability over the wide temperature makes these molecules promising materials for potential applications. At lower temperatures, individual subchromophoric properties subside because of the reduced dihedral angle of biphenyl, and fluorescence from the whole molecule becomes dominant.

Interfacial versus Bulk Properties of Hole-Transporting Materials for Perovskite Solar Cells: Isomeric Triphenylamine-Based Enamines versus Spiro-OMeTAD

Here, we report on three new triphenylamine-based enamines synthesized by condensation of an appropriate primary amine with 2,2-diphenylacetaldehyde and characterized by experimental techniques and density functional theory (DFT) computations. Experimental results allow highlighting attractive properties including solid-state ionization potential in the range of 5.33-5.69 eV in solid-state and hole mobilities exceeding 10^-3 cm²/V·s, which are higher than those in spiro-OMeTAD at the same electric fields. DFT-based analysis points to the presence of several conformers close in energy at room temperature. The newly synthesized hole-transporting materials (HTMs) were used in perovskite solar cells and exhibited performances comparable to that of spiro-OMeTAD. The device containing one newly synthesized hole-transporting enamine was characterized by a power conversion efficiency of 18.4%. Our analysis indicates that the perovskite-HTM interface dominates the properties of perovskite solar cells. PL measurements indicate smaller efficiency for perovskite-to-new HTM hole transfer as compared to spiro-OMeTAD. Nevertheless, the comparable power conversion efficiencies and simple synthesis of the new compounds make them attractive candidates for utilization in perovskite solar cells.

Incorporating Photochromic Triphenylamine into a Zirconium-Organic Framework for Highly Effective Photocatalytic Aerobic Oxidation of Sulfides

A zirconium-based metal-organic framework (MOF) was successfully constructed via solvothermal assembly of a triphenylamine-based tricarboxylate ligand and Zr(IV) salt, the structure simulation of which revealed that it possesses a two-dimensional layered framework with a relatively rare dodecnuclear Zr₁₂ cluster as the inorganic building unit. The inherent photo-responsive property derived from the incorporated photochromic triphenylamine groups combined with its high stability makes the constructed MOF an efficient heterogeneous photocatalyst for the oxidation of sulfides, which is a fundamentally important reaction type in both environmental and pharmaceutical industries. The photocatalytic activity of the constructed MOF was first investigated under various conditions with thioanisole as a representative sulfide substrate. The MOF exhibited both high efficiency and selectivity on aerobic oxidation of thioanisole in methanol utilizing molecular oxygen in air as the oxidant under blue light irradiation for 10 h. Its high photocatalytic performance was also observed when extending the sulfide substrate to diverse thioanisole derivatives and even a sulfur-containing nerve agent simulant (2-chloroethyl ethyl sulfide). The high photocatalytic efficiency and selectivity to a broad set of sulfide substrates make the triphenylamine-incorporating zirconium-based MOF a highly promising heterogeneous photocatalyst.

Dicyanotriphenylamine-Based Polyimides as High-Performance Electrodes for Next Generation Organic Lithium-Ion Batteries

Aromatic polyimide (PI) derivatives have recently been investigated as redox-active electrode materials for Li-ion batteries because of their high thermal stability and thermo-oxidative stability complemented by excellent solvent resistance, good electrical and mechanical properties, and chemical resistance. In this work, we report two PI derivatives from a newly synthesized 4,4'-diamino-3″,4″-dicyanotriphenylamine (DiCN-TPA) monomer and two dianhydrides, pyromellitic dianhydride (PMDA) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (NTCDA); designated as TPA-PMPI and TPA-NTCPI, respectively, as electrode materials for Li-ion batteries. Characterizations of the PIs reveal excellent thermal stability and bipolar property. The incorporation of DiCN-TPA into the polymer structure resulted to a disordered chain arrangement, thus giving high glass transition temperatures (T_g). Electrochemical performance tests reveal that TPA-NTCPI cathode delivered a reversible specific capacity of 150 mAh g^-1 at 0.1 A g^-1 and exhibited a stability up to 1000 cycles. On the other hand, TPA-PMPI anode delivered a high specific capacity of up to 1600 mAh g^-1 at 0.1 A g^-1 after 100 cycles. The electrochemical performance of TPA-NTCPI cathode and TPA-PMPI anode are both among the best compared with other reported aromatic PI-based electrodes. The long cycle lifetime and excellent battery performance further suggest that TPA-NTCPI and TPA-PMPI are promising organic electrode materials for next generation Li-ion batteries.

Broadband Visible Light-Absorbing [70]Fullerene-BODIPY-Triphenylamine Triad: Synthesis and Application as Heavy Atom-Free Organic Triplet Photosensitizer for Photooxidation

A broadband visible light-absorbing [70]fullerene-BODIPY-triphenylamine triad (C70-B-T) has been synthesized and applied as a heavy atom-free organic triplet photosensitizer for photooxidation. By attaching two triphenylmethyl amine units (TPAs) to the π-core of BODIPY via ethynyl linkers, the absorption range of the antenna is extended to 700 nm with a peak at 600 nm. Thus, the absorption spectrum of C70-B-T almost covers the entire UV-visible region (270-700 nm). The photophysical processes are investigated by means of steady-state and transient spectroscopies. Upon photoexcitation at 339 nm, an efficient energy transfer (ET) from TPA to BODIPY occurs both in C70-B-T and B-T, resulting in the appearance of the BODIPY emission at 664 nm. Direct or indirect (via ET) excitation of the BODIPY-part of C70-B-T is followed by photoinduced ET from the antenna to C70, thus the singlet excited state of C70 (1C70*) is populated. Subsequently, the triplet excited state of C70 (3C70*) is produced via the intrinsic intersystem crossing of C70. The photooxidation ability of C70-B-T was studied using 1,5-dihydroxy naphthalene (DHN) as a chemical sensor. The photooxidation efficiency of C70-B-T is higher than that of the individual components of C70-1 and B-T, and even higher than that of methylene blue (MB). The photooxidation rate constant of C70-B-T is 1.47 and 1.51 times as that of C70-1 and MB, respectively. The results indicate that the C70-antenna systems can be used as another structure motif for a heavy atom-free organic triplet photosensitizer.

How Does Bridging Core Modification Alter the Photovoltaic Characteristics of Triphenylamine-Based Hole Transport Materials? Theoretical Understanding and Prediction

Perovskite solar cells have gained immense interest from researchers owing to their good photophysical properties, low-cost production, and high power conversion efficiencies. Hole transport materials (HTMs) play a dominant role in enhancing the power conversion efficiencies (PCEs) and long diffusion length of holes and electrons in perovskite solar cells. In hole transport materials, modification of π-linkers has proved to be an efficient approach for enhancing the overall PCE of perovskite solar cells. In this work, π-linker modification of a recently synthesized H-Bi molecule (R) is achieved with novel π-linkers. After structural modifications, ten novel HTMs (HB1-HB10) with a D-π-D backbone are obtained. The structure-property relationship, and optoelectronic and photovoltaic characteristics of these newly designed hole transport materials are examined comprehensively and compared with reference molecules. In addition, different geometric parameters are also examined with the assistance of density functional theory (DFT) and time-dependent DFT. All the designed molecules exhibit narrow HOMO-LUMO energy gaps (E_g =2.82-2.99 eV) compared with the R molecule (E_g =3.05 eV). The designed molecules express redshifting in their absorption spectra with low values of excitation energy, which in return offer high power conversion efficiencies. Further, density of states and molecular electrostatic potential analysis is performed to locate the different charge sites in the molecules. The reorganizational energies of holes and electrons are found to have good values, suggesting that these novel designed molecules are efficient hole transport materials for perovskite solar cells. In addition, the low binding energy values of the designed molecules (compared with R) offer high current charge density. Finally, complex study of HB9:PC₆₁ BM is also undertaken to understand the charge transfer between the molecules of the complex. The results of all analyses advocate that these novel designed HTMs are promising candidates for the construction of future high-performance perovskite solar cells.

Effect of Bulky Functional Groups on Donor and Acceptor Interactions and their Photoluminescence Properties

Material designs that use donor and acceptor units are often found in organic optoelectronic devices. Molecular level insight into the interactions between donors and acceptors are crucial for understanding how such interactions can modify the optical properties of the organic optoelectronic materials. In this paper, tris(4-(tert-butyl)phenyl)amine (pTPA) was synthesized as a donor in order to compare with unmodified triphenylamine (TPA) in a donor-acceptor system by having 2,4,6-triphenyl-1,3,5-triazine (TRZ) as an acceptor. Dimerization of donors and acceptors occurred in solvent when the concentration of solute is high. At 0 K, using a polarizable continuum model, the nitrogen atom of TPA is found to stack on top of the center of triazine of TRZ, whereas such alignment is offset in pTPA and TRZ. We attributed such alignment in TPA-TRZ as the result of attractive interactions between partial localization of 2p_z electrons at the nitrogen atom of TPA and the π deficiency of triazine in TPA-TRZ. By taking into account random motions of the solvent effect at 300 K in quantum molecular dynamics and classical molecular dynamics simulations to interpret the marked difference in emission spectra between TPA-TRZ and pTPA-TRZ, it was revealed that the attractive interaction between pTPA and TRZ in toluene is weaker than TPA and TRZ. Because of the weaker attractive interaction between pTPA and TRZ in toluene, the dimers adopted numerous ground state conformations resulting in broad emission bands superimposed with multiple small Gaussian peaks. This is in contrast to TPA-TRZ which has only one dominant dimer conformation. This study demonstrates that the strength of intermolecular interactions between donors and acceptors should be taken into consideration in designing supramolecular structures.

Multifunctional Hypercrosslinked Porous Organic Polymers Based on Tetraphenylethene and Triphenylamine Derivatives for High-Performance Dye Adsorption and Supercapacitor

We successfully prepared two different classes of hypercrosslinked porous organic polymers (HPPs)-the tetraphenylethene (TPE) and (4-(5,6-Diphenyl-1H-Benzimidazol-2-yl)-triphenylamine (DPT) HPPs-through the Friedel-Crafts polymerization of tetraphenylethene and 4-(5,6-diphenyl-1H-benzimidazol-2-yl)-triphenylamine, respectively, with 1,4-bis(chloromethyl)benzene (Ph-2Cl) in the presence of anhydrous FeCl₃ as a catalyst. Our porous materials exhibited high BET surface areas (up to 1000 m² g^-1) and good thermal stabilities. According to electrochemical and dyes adsorption applications, the as-prepared DPT-HPP exhibited a high specific capacitance of 110 F g^-1 at a current density of 0.5 A g^-1, with an excellent cycling stability of over 2000 times at 10 A g^-1. In addition, DPT-HPP showed a high adsorption capacity up to 256.40 mg g^-1 for the removal of RhB dye from water.

Enhanced Oxygen Reduction Reaction Performance Using Intermolecular Forces Coupled with More Exposed Molecular Orbitals of Triphenylamine in Co-porphyrin Electrocatalysts

Triphenylamine (TPA) has often been used as a building block to construct functional organic materials yet is rarely employed in oxygen reduction reaction (ORR) due to its strong electron-donating ability. This versatile segment bears a three-dimensional spatial structure whose effect has not been fully explored in catalytic systems. To this end, five symmetric cobalt porphyrins with carbazole and TPA derivatives have been synthesized and their ORR performance has been evaluated in acid medium. It was found that all compounds produced mainly hydrogen peroxide in oxygen reduction, with CP1 attaching benzyl derivatives and XCP4 possessing TPA-carbazole substituents at the meso-position of porphyrin, showing similar but more positive ORR potential as compared to the other analogues. Importantly, XCP4 achieved the greatest response current and the largest electron transfer numbers and H₂O₂ yields among the investigated molecules. Detailed electrochemical measurements suggested that the dipole-induced partial charges on the porphyrin in tandem with the more exposed molecular orbitals on TPA contributed to this enhancement, with the former attracting more protons to the affinity of reactive sites and the latter increasing the collision frequency between the electrocatalyst and H⁺ in solution. This is the first attempt to integrate the intermolecular forces with more exposed molecular orbitals in altering the electrochemical process.

Synthesis and fluorescence properties of two dendritic molecules based on naphthalimide and triphenylamine

Artificial light-harvesting systems have attracted great interest in biological photosynthesis and photo-voltaic devices areas due to their unique structures, easy purification, low-cost, and convenient processing abilities. Here, two dendritic molecules based on triphenylamine and naphthalimide have been designed and synthesized, their structures were confirmed by ¹ H NMR, ESI-MS, and high resolution mass spectrometry. In these molecules, triphenylamine units perform as the electron donor moiety, and naphthalimide units perform as the electron acceptor. The obvious quenched fluorescence intensity and considerably shortened lifetime of the dendritic molecules combined with the molecular frontier orbital energy levels proved that the dendritic molecules not only are good candidates as hole-transporting materials but also are two excellent photo-induced electron transfer materials. Therefore, it is believed that these dendritic molecules have potential application value in photo-voltaic devices.

Novel Photoinitiators Based on Benzophenone-Triphenylamine Hybrid Structure for LED Photopolymerization

In this study, a new generation of photoinitiator (PI) based on hybrid structures combining benzophenone and triphenylamine is proposed. Remarkably, these photoinitiators (noted monofunctional benzophenone-triphenylamine (MBP-TPA) and trifunctional benzophenone-triphenylamine (TBP-TPA)) are designed and developed for the photopolymerization under light-emitting diodes (LEDs). Benzoyl substituents connected with triphenylamine moiety contribute to the excellent absorption properties which results in both high final conversions and polymerization rates in free radical photopolymerization (FRP). Remarkably, TBP-TPA owning trifunctional benzophenone group exhibits a better Type II PI behavior than well-known 2-isopropylthioxanthone for photopolymerization under LED@365 and 405 nm irradiation. FRP and cationic photopolymerization of TBP-TPA-based systems are applied on 3D printing experiments, and good profiles of the 3D patterns are observed. The high molecular weight of TBP-TPA associated with it trifunctional character can also be very interesting for a better migration stability of PIs that is a huge challenge. The development of this new generation of photoinitiators based on benzophenone hybrid structures is a real breakthrough. It reveals that the novel versatile photoinitiators based on benzophenone-triphenylamine hybrid structures have great potentials for future industrial applications (e.g., 3D printing, composites, etc.).

PDI-Based Hexapod-Shaped Nonfullerene Acceptors for the High-Performance As-Cast Organic Solar Cells

Three hexapod-shaped PDI-hexamers (PSM1, PSM2, and PSM3) with a diphenylmethylene-bridged triphenylamine (TPA) core and six peripheral PDI subunits have been designed and synthesized. The influence of different peripheral PDI subunits on the morphology and crystallinity of acceptors is investigated. Distinctly different from the previously reported PDI trimers with a TPA core, which exhibit amorphous morphologies, these hexapod-shaped acceptors display improved crystallinities and photophysical properties. Our studies have shown that PSM3 with six peripheral thiophene-fused PDI subunits gives the best result. The as-cast blend films of PBDB-T and PSM3, which possess appropriate phase separation and higher crystallinity, show high and balanced charge mobilities. As expected, OSCs with PBDB-T:PSM3 as the active layer achieve the highest power conversion efficiency of 6.71% among these three acceptors, which is the highest one in TPA-based acceptors and one of the best for the as-cast OSCs based on PDI derivatives.

Solution-Processable Copolymers Based on Triphenylamine and 3,4-Ethylenedioxythiophene: Facile Synthesis and Multielectrochromism

In comparison with traditional inorganic electrochromic materials, organic polymers offer advantages such as fast switching speed, flexibility, lightweightness, low cost and nontoxicity, solution-processability, and color tunability. Herein, a series of hyper-branched copolymers are synthesized from triphenylamine and 3,4-ethylenedioxythiophene with different feed ratios via iron(III) chloride (FeCl₃ )-mediated oxidative polymerization. The resultant organic-soluble polymers are easily processable and their corresponding electrochromic devices are found to be stable with limited degradation upon 2500 cycles. In addition to their facile synthesis to achieve solution-processable polymers, studies also show that the polymers exhibit multielectrochromic properties and give rise to five colored states upon oxidative-doping by applying an external voltage between 0 and 2.0 V, providing an interesting example of polymers with unique electrochromic switching among up to five colors, from yellow at the neutral state, to pale green, pale purple, orange, and finally gray.

Lewis-Acid Doping of Triphenylamine-Based Hole Transport Materials Improves the Performance and Stability of Perovskite Solar Cells

Highly efficient perovskite solar cells (PSCs) fabricated in the classic n-i-p configuration generally employ triphenylamine-based hole-transport layers (HTLs) such as spiro-OMeTAD, PTAA, and poly-TPD. Controllable doping of such layers has been critical to achieve increased conductivity and high device performance. To this end, LiTFSI/tBP doping and subsequent air exposure is widely utilized. However, this approach often leads to low device stability and reproducibility. Departing from this point, we introduce the Lewis acid tris(pentafluorophenyl)borane (TPFB) as an effective dopant, resulting in a significantly improved conductivity and lowered surface potential for triphenylamine-based HTLs. Here, we specifically investigated spiro-OMeTAD, which is the most widely used HTL for n-i-p devices, and revealed improved power conversion efficiency (PCE) and stability of the PSCs. Further, we demonstrated the applicability of TPFB doping to other triphenylamine-based HTLs. Spectroscopic characterizations reveal that TPFB doping results in significantly improved charge transport and reduced recombination losses. Importantly, the TPFB-doped perovskite devices retained near 85% of the initial PCE after 1000 h of storage in the air, while the conventional LiTFSI-doped device dropped to 75%. Finally, we give insight into utilizing other similar molecular dopants such as fluorine-free triphenylborane and phosphorus-centered tris(pentafluorophenyl)phosphine (TPFP) by density functional theory analysis underscoring the significance of the central boron atom and fluorination in TPFB for the formation of Lewis acid-base adducts.

Three New Metal Complexes with Imidazole-Containing Tripodal Ligands as Fluorophores for Nitroaromatics- and Ion-Selective Sensing

Three new metal-organic complexes [Cd(TIPA)(suc)0.5(NO3)·1/2H2O]n (1), [Ni(TIPA)(tda)0.5(H2O)·1/4H2O]n (2) and [Cd(TIPA)(tda)0.5·11/2H2O] (3) were synthesized via rigid tripodal ligand tris(4-(1H-imidazol-1-yl)phenyl)amine (TIPA) and three dicarboxylic acids; either succinic acid (H2suc) or 2,5-thiophenedicarboxylic acid (H2tda). Crystallographic data for 1 - 3 reveal three-dimensional (3D) networks and channels in the structures. The structure of 2 is unique featuring an interpenetrating 2D network, 2D + 2D → 3D, with the two associated 2D networks existing in two opposite spiral channels. TGA plots exhibit a loss of mass corresponding to the loss of the solvated water molecules in the 100 - 200 °C temperature region and begin to lose additional fragments only at T > 300 °C revealing the robust nature of the 3D framework in the complexes. The metal-organic frameworks (MOFs) are screened for their potential application in the detection and removal of environmentally hazardous industrial pollutants. Fluorescence emission spectra for 1 and 2 show that the two MOFs are capable of sensing nitrobenzene (NB), with the nickel complex 2 exhibiting significantly higher sensing ability. Powder XRD data measured for 1 and 2 and those of NB-treated 1 and 2 show significant differences in their patterns, providing further support for the strong interaction between the MOF complexes and NB. The fluorescence emission observed for 1 is more effectively quenched by the presence of Fe3+ than the series of 17 other metal ions investigated. Complex 3 possesses some ability to adsorb inorganic pollutants.

Highly Stable and Rapid Switching Electrochromic Thin Films Based on Metal-Organic Frameworks with Redox-Active Triphenylamine Ligands

Metal-organic frameworks (MOFs), known for their tailorable porous structures and large specific surface areas, are appealing for electrochromic applications as their abundant pores may greatly benefit the charge transport required for electrochromic switching. Herein, for the first time, a simple, scalable, and cost-effective electrochemical deposition method for fabrication of high-performance and durable MOFs-based electrochromic films with redox-active ligands was developed. The fabricated film can achieve rapid switching speed (both coloration and bleaching time <5 s) because the inherent cavities of the MOFs greatly facilitate ion insertion and extraction. In addition, the film constructed with optimized parameters shows a high optical contrast of 65%@700 nm and can be stably switched for 1000 cycles with <5% contrast attenuation, which is by far the best cycling performance for MOFs-based electrochromic materials ever reported. Furthermore, our method enables the scalable preparation of large-area MOFs-based electrochromic thin films without using large high-pressure reaction vessels, and the as-prepared film in this work could be switched well between colored and bleached states. This new method, therefore, opens up a new avenue to broaden the use of MOFs-based thin films for electrochromic applications.

Facile Synthesis of Triphenylamine Based Hyperbranched Polymer for Organic Field Effect Transistors

In this study, we reported the synthesis and characterization of a novel hyperbranched polymer (HBPs) tris[(4-phenyl)amino-alt-4,8-bis(5-(2-ethylhexyl)thiophen-2-yl)benzo[1,2-b;4,5-b']dithiophene] (PTPABDT) composed of benzo[1,2-b:4,5-b']dithiophene (BDT) and triphenyleamine (TPA) constituent subunits by A₃ + B₂ type Stille's reaction. An estimated optical band gap of 1.69 eV with HOMO and LUMO levels of -5.29 eV and -3.60 eV, respectively, as well as a high thermal stability up to 398 °C were characterized for the synthesized polymer. PTPABDT fabricated as an encapsulated top gate/bottom contact (TGBC), organic field effect transistors (OFET) exhibited a p-type behavior with maximum field-effect mobility (µmax) and an on/off ratio of 1.22 × 10^-3 cm² V^-1 s^-1 and 7.47 × 10², respectively.

Photophysical and Electroluminescence Characteristics of Polyfluorene Derivatives with Triphenylamine

In this work, polymers of poly[(9,9-dioctylfluorenyl-2,7-diyl)-co-triphenylamine] with side chains containing: pyrene (C1), diphenyl (C2), naphthalene (C3), and isopropyl (C6) structures were synthesized via a Suzuki coupling reaction. The structures were verified using NMR and cyclic voltammetry measurements provide the HOMO and LUMO of the polymers. The polymer with pyrene (C1) and naphthalene (C3) produced photoluminescence in the green while the polymer with the side chain containing diphenyl (C2) and isopropyl (C6) produce dual emission peaks of blue-green photoluminescence (PL). In order to examine the electroluminescence properties of the polymers, the solutions were spin-coated onto patterned ITO anode, dried, and subsequently coated with an Al cathode layer to form pristine single layer polymer LEDs. The results are compared to a standard PFO sample. The electroluminescence spectra resemble the PL spectra for C1 and C3. The devices of C2, C3, and C6 exhibit voltage-dependent EL. An additional red emission peak was detected for C2 and C6, resulting in spectra with peaks at 435 nm, 490 nm, and 625 nm. The effects of the side chains on the spectral characteristics of the polymer are discussed.

Synthesis and Characterization of Novel Triarylamine Derivatives with Dimethylamino Substituents for Application in Optoelectronic Devices

Two novel triphenylamine-based derivatives with dimethylamino substituents, N, N'-bis(4-dimethylaminophenyl)- N, N'-bis(4-methoxyphenyl)-1,4-phenylenediamine (NTPPA) and N, N'-bis(4-dimethylaminophenyl)- N, N'-bis(4-methoxyphenyl)-1,1'-biphenyl-4,4'-diamine (NTPB), were readily prepared for investigating the optical and electrochromic behaviors. These two obtained materials were introduced into electrochromic devices accompanied with heptyl viologen (HV), and the devices demonstrate a high average coloration efficiency of 287 cm²/C and electrochemical stability. Besides, NTPB/HV was further used to fabricate electrofluorochromic devices with a gel type electrolyte, and exhibit a controllable and high photoluminescence contrast ratio ( I_off/ I_on) of 32.12 from strong emission to truly dark by tuning the applied potential in addition to a short switching time of 4.9 s and high reversibility of 99% after 500 cycles.

Triphenylamine-Merocyanine-Based D1-A1-π-A2/A3-D2 Chromophore System: Synthesis, Optoelectronic, and Theoretical Studies

donor⁻acceptorDonor⁻acceptor⁻π⁻acceptor⁻donor (D1-A1-π-A2/A3-D2)-type small molecules, such TPA-MC-2 and TPA-MC-3, were designed and synthesized starting from donor-substituted alkynes (TPA-MC-1) via [2 + 2] cycloaddition-retroelectrocyclization reaction with tetracyanoethylene (TCNE) and 7,7,8,8-tetracyanoquinodimethane (TCNQ) units, respectively. TPA-MC-2 and TPA-MC-3 chromophores differ on the A2/A3 acceptor subunit, which is 1,1,4,4-tetracyanobutadiene (TCBD) and a dicyanoquinodicyanomethane (DCQDCM), respectively. Both the derivative bearing same donors D1 (triphenylamine) and D2 (trimethylindolinm) and also same A1 (monocyano) as an acceptor, tetracyano with an aryl rings as the π-bridging moiety. The incorporation of TCNE and TCNQ as strong electron withdrawing units led to strong intramolecular charge-transfer (ICT) interactions, resulting in lower LUMO energy levels. Comparative UV⁻Vis absorption, fluorescence emission, and electrochemical and computational studies were performed to understand the effects of the TCNE and TCNQ subunits incorporated on TPA-MC-2 and TPA-MC-3, respectively.

Design, Synthesis, and Electrofluorochromism of New Triphenylamine Derivatives with AIE-Active Pendent Groups

Triphenylamine (TPA) and 4,4'-dimethoxy-triphenylamine (TPAOMe) derivatives were successfully linked with two high-performance AIEgens, triphenylethylene (TPE) and benzo[ b]thiophene-1,1-dioxide (BTO), to obtain four aggregation-induced emission and electro-active materials, TPETPA, BTOTPA, TPETPAOMe, and BTOTPAOMe. The effects on photoluminescence characteristics and electrochromic (EC) and electrofluorochromic (EFC) behaviors in cross-linking gel-type devices derived from the prepared materials were systematically investigated. Furthermore, heptyl viologen was introduced into the EFC devices to enhance EC performance including lower working potential, faster switching time, and superior stability.

New Triphenylamine-Based Oligomeric Schiff Bases Containing Tetraphenylsilane Moieties in the Backbone

Three new triphenylamine-based oligomeric Schiff bases (polySB1, polySB2 and polySB3) containing tetraphenylsilane core (TPS-core) in the main chain were obtained from TPS-core-based diamines and bis(4-formylphenyl)phenylamine by a high-temperature polycondensation reaction. These new oligomers were structurally characterized by FT-IR, NMR and elemental analysis. All polySBs were highly soluble in common organic solvents, such as chloroform, tetrahydrofuran and chlorobenzene. Samples showed moderate molecular average molecular weight (Mw) and a high thermal stability above 410 °C. Likewise, polySBs showed absorption near 400 nm in the UV-vis range and photoluminescence. The HOMO levels and band-gap values were found in the ranges of -6.06 to -6.18 eV and 2.65⁻2.72 eV, respectively. The lowest band-gap value was observed for polySB2, which could be attributed to a more effective π-conjugation across the main chain. The results suggest that silicon-containing polySBs are promising wide-band-gap semiconductors materials for optoelectronic applications.

Electrochromism in Electropolymerized Films of Pyrene-Triphenylamine Derivatives

Two star-shaped multi-triphenylamine derivatives 1 and 2 were prepared, where 2 has an additional phenyl unit between a pyrene core and surrounding triphenylamine units. The oxidative electropolymerization of 1 and 2 occurred smoothly to give thin films of polymers P1 and P2. The electrochemistry and spectroelectrochemistry of P1 and P2 were examined, showing two-step absorption spectral changes in the near-infrared region. The electrochromic properties, including contrast ratio, response time, and cyclic stability of P1 and P2 were investigated and compared. Thin film of P2 displays slightly better electrochromic performance than P1, with a contrast ratio of 45% at 1475 nm being achieved.