Triphenylamine Units Research Articles

Branched Electron-Donor Core Effect in D-π-A Star-Shaped Small Molecules on Their Properties and Performance in Single-Component and Bulk-Heterojunction Organic Solar Cells †

Star-shaped donor-acceptor molecules are full of promise for organic photovoltaics and electronics. However, the effect of the branching core on physicochemical properties, charge transport and photovoltaic performance of such donor-acceptor materials in single-component (SC) and bulk heterojunction (BHJ) organic solar cells has not been thoroughly addressed. This work shows the comprehensive investigation of six star-shaped donor-acceptor molecules with terminal hexyldicyanovinyl blocks linked through 2,2′-bithiophene π-conjugated bridge to different electron-donating cores such as the pristine and fused triphenylamine, tris(2-methoxyphenyl)amine, carbazole- and benzotriindole-based units. Variation of the branching core strongly impacts on such important properties as the solubility, highest occupied molecular orbital energy, optical absorption, phase behavior, molecular packing and also on the charge-carrier mobility. The performance of SC or BHJ organic solar cells are comprehensively studied and compared. The results obtained provide insight on how to predict and fine-tune photovoltaic performance as well as properties of donor-acceptor star-shaped molecules for organic solar cells.

Synthesis and electropolymerization of 3-arylthieno[3,2-b]thiophenes and triphenylamine based comonomers

Electrochemical polymerizations of thieno[3,2-b]thiophenes (TT), named PhTTTPA, CH3OPhTTTPA and CNPhTTTPA, possessing pH, 4-CH3OPh, 4-CNPh and triphenylamine (TPA) units, were performed and their corresponding polymers P[PhTTTPA], P[CH3OPhTTTPA] and P[CNPhTTTPA] were obtained, respectively. The polymer films were characterized by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS) and spectroelectrochemical measurements, which suggested that while the presence of strong electron donating TPA unit provided them with better electrochemical reversibility, strong electron withdrawing -CN group lowered the oxidation potential of P[CNPhTTTPA] along with enhancement of its charge storage character.

Multifunctional Materials Serving as Efficient Non‐Doped Violet‐Blue Emitters and Host Materials for Phosphorescence

Efficient multifunctional materials acting as violet-blue emitters, as well as host materials for phosphorescent OLEDs, are crucial but rare due to demand that they should have high first singlet state (S1 ) energy and first triplet state (T1 ) energy simultaneously. In this study, two new violet-blue bipolar fluorophores, TPA-PI-SBF and SBF-PI-SBF, were designed and synthesized by introducing the hole transporting moiety triphenylamine (TPA) and spirobifluorene (SBF) unit that has high T1 into high deep blue emission quantum yield group phenanthroimidazole (PI). As the results, the non-doped OLEDs based on TPA-PI-SBF exhibited excellent EL performance with a maximum external quantum efficiency (EQEmax ) of 6.76 % and a violet-blue emission with Commission Internationale de L'Eclairage (CIE) of (0.152, 0.059). The device based on SBF-PI-SBF displayed EQEmax of 6.19 % with CIE of (0.159, 0.049), which nearly matches the CIE coordinates of the violet-blue emitters standard of (0.131, 0.046). These EL performances are comparable to the best reported non-doped deep or violet-blue emissive OLEDs with CIEy<0.06 in recent years. Additionally, the green, yellow and red phosphorescent OLEDs with TPA-PI-SBF and SBF-PI-SBF as host materials achieved a high EQEmax of about 20 % and low efficiency roll-off at the ultra-high luminance of 10 000 cd m-2 . These results provided a new construction strategy for designing high-performance violet-blue emitters, as well as efficient host materials for phosphorescent OLEDs.

Preparation of Poly(arylamino‐quinone) Polymer and Its Electrochemical Properties as a Cathode Material for Lithium Ion Battery

AbstractThe exploration of organic materials for electrochemical energy storage has attracted much attention, and our studies focus on quinone‐based polymer that is employed as the electrode materials for lithium‐ion batteries. In this article, two poly(arylamino‐quinone) polymers are prepared by Michael addition polymerization reaction. The constructed poly(arylamino‐quinone) polymers contained the quinone units in arylamine‐linked conjugated skeleton, which possess the branched molecular structure for poly (tris(4‐aminophenyl)amine‐benzoquinone) (PAQ1) and the linear molecular structure for poly (p‐phenylenediamine‐benzoquinone) (PAQ2), respectively. As explored as the organic cathode materials for lithium‐ion batteries, PAQ1 with granular morphology exhibits the discharge capacity of 429.6 mAh. g−1 in the first cycle and the improved average discharge potential. Also, it shows that the stable cycling stability after the capacity attenuation in the initial cycles and the high current rate performances as comparing to PAQ2. It can be ascribed to the introduction of triphenylamine unit in polymer and the assembled granular morphology, which contributes to improved electrochemical performances for PAQ1.

Defect Passivation by a D–A–D Type Hole-Transporting Interfacial Layer for Efficient and Stable Perovskite Solar Cells

In this work, we present a series of donor–acceptor–donor type of small molecules (BDAD, ODAD, and DDAD) based on the triphenylamine (TPA) and dithienopyrrolobenzothiadiazole (DTPBT) units, which are distinguished by alkyl chains of different lengths grafted on the DTPBT unit, as a hole-transporting interfacial layer for perovskite solar cells (PSCs). The incorporation of the DTPBT units is beneficial for not only carrier transportation but also potential defects passivation via Pb–N/S interactions. A champion power conversion efficiency (PCE) of 22.76% has been achieved on PSCs based on BDAD with the n-butyl side chains. Those devices without encapsulation retain over 96% of their initial PCE for more than 120 days. The improved stability is attributed to the restraint of the generation of δ-phase perovskite as supported by the grazing incidence wide-angle X-ray scattering analyses.

High-performance non-doped pure-blue electroluminescent device based on bisphenanthroimidazole derivative with twisted donor-acceptor structure

Abstract The development of efficient pure-blue emitters is of great significance for achieving high-quality display and lighting. Herein, a pure-blue emitter TPA-DPPI comprised of bisphenanthroimidazole and triphenylamine units with bipolar carrier transport property is designed and synthesized. For the two phenanthroimidazole units, one acts as the electron acceptor moiety, and the other is introduced to twist the molecule in order to suppress the intermolecular interactions in neat film. Highly twisted molecular configuration endows the compound with a high photoluminescence quantum efficiency yield of 0.56 in neat film. The non-doped device using TPA-DPPI as an emissive layer shows a pure-blue emission with a Commission International de l'Eclairage coordinates of (0.146, 0.097) and a high external quantum efficiency of 5.20%.

A computational and experimental investigation of donor-acceptor BODIPY based near-infrared fluorophore for in vivo imaging

TD-DFT quantum calculation was performed to predict and/or illustrate the electronic transition, the related absorption and emission maxima of some pyrrole-difluoroboron derivatives with different electron donor–acceptor unit or π-conjugated degree. Upon the calculated results, a new near infrared (NIR) fluorophore (abbreviated as TPBD-BP) was designed and fabricated through linking triphenylamine and pyrrole-difluoroboron units to benzothiadiazole (BTD) backbone. The fluorescence of TPBD-BP in solid state centered at 932 nm, which was 985 nm for TPBD-BP nanoparticles (TPBD-BP dots) encapsulated in PEG-6000. The fluorescence of TPBD-BP in both solid state and dots exhibited off-peak tail emission to NIR-II region (extended to 1300 nm). The TPBD-BP dots showed excellent water solubility, biocompatibility and aggregation induced emission (AIE), which was suitable to be applied in vivo imaging. NIR-II emission signal of TPBD-BP dots can be observed in the reproductive organ of normal nude mice after tail vein injection. This attractive combination of computational and experimental investigation would help to develop new-typed small-molecular NIR fluorophores.

Thermally Activated Delayed Fluorescence Properties of Trioxoazatriangulene Derivatives Modified with Electron Donating Groups

AbstractWith the aim of achieving high‐performance thermally activated delayed fluorescence, a series of trioxoazatriangulene derivatives are systematically developed by modifying the donor substituents. The emission colors are shifted from green to greenish‐yellow and to yellow with rather broad spectral widths of 70–95 nm by introducing carbazole, triphenylamine, or diphenylamine donor units, indicating that each emission originates from a charge‐transfer transition. On the other hand, the trioxoazatriangulene modified with three diphenylamines shows orange emission with a narrow emission spectrum (45 nm), suggesting that the transition mainly originates from a multiple resonance effect.

Oxygen‐Bridged Triphenylamine Units Tuning the Photophysical Properties of Classical Phosphorescent Iridium(III) Complex

AbstractA new yellow phosphorescent iridium(III) complex Ir(ppybop)2acac with two oxygen‐bridged triphenylamine units were prepared and investigated. The cyclometalating ligand ppybop was synthesized by the efficient Suzuki‐Miyaura cross‐coupling reaction of oxygen‐bridged triarylamine unit based boron reagent 1‐a and 2‐(4‐Bromophenyl)pyridine, and the acetylacetone (acac) was used as an auxiliary ligand. Notably, the complex Ir(ppybop)2acac measured with a fluorescence spectrophotometer can show a larger redshift emission (λem=568 nm), a narrower full width at half maximum (FWHM=59 nm), a longer emission lifetime (τ[b]=3127 ns) and a better solubility in comparison with the classical green complex Ir(ppy)2acac (λem=520 nm, FWHM=70 nm, τ[b]=1206 ns). In addition, the DFT calculation results indicate that the strong electron‐donating ability of the unit can lead to the unusual ligand‐to‐metal charge transfer (3LMCT) excited state characteristics of Ir(ppybop)2acac, which is completely different from the metal‐to‐ligand charge transfer (3MLCT) in Ir(ppy)2acac. This result can provide a new strategy for the design of new phosphorescent iridium(III) complexes.

Triphenylamine-Contained Multiporous Polyimide: Its Preparation and Application as Anode for Lithium-Ion Storage

Abstract The three-dimensional (3D) multiporous structure polyimides were obtained by introducing of the triphenylamine (TPA) unit as linkage in the pyromellitic-based polyimide (N1) and the naphthalene-1,4,5,8-tetracarboxylic-based polyimides (N2), respectively. Then, the functional polyimides were explored as the anode of lithium ion batteries instead of as traditional cathode. As a result, the obtained triphenylamine-based polyimides exhibited a good reversible capacity and remarkably improved rate performance. Especially for the porous N1, it delivered a gradually increased capacity of up to 349 mAh/g during the cycle testing and a rate capacity of 400 mAh/g at an even high current density of 500 mA/g. Significant electrochemical performances for the triphenylamine-contained polyimide could be ascribed to the unique polyimide chemical structure and the constructed 3D multiporous structure with the high surface area (738 m2/g for N1 and 456 m2/g for N2), which benefited to excellent Li+ diffusion kinetics in porous electrode. This makes it promising as anode of rechargeable batteries with the remarkably electrochemical performances.

Novel naphthalimide derived fluorescent probe based on aggregation-induced emission for turn-on detection of hydrogen sulfide

Abstract Two novel aggregation-induced emission (AIE) based fluorescent probes, TPANI-DNs and PCZNI-DNs, have been designed and synthesized for “turn-on” detection of H2S. Chromophore napthalimide fused triphenylamine (or phenylcarbazole) unit as fluorophore in combination with 2,4-dinitrobenzenesulfonyl as recognition moiety constructed probes. The design strategy of the twisted D-π-A structure can efficiently transform the aggregation-caused quenching (ACQ) system into the AIE system by strengthening the restriction of intramolecular motion and preventing the intermolecular π-π stacking. The consequences showed that both TPANI-DNs and PCZNI-DNs displayed large stokes shift (135 nm and 120 nm, respectively), high selective and sensitive detection. The response mechanisms and fluorescent properties were further investigated through the time-dependent density functional theory (TDDFT). Importantly, since the strong AIE properties, a H2S test board has been prepared and used to detect H2S onsite easily and sensitively, displaying potential practical applications.

Triphenylamine- and triazine-containing hydrogen bonded complexes: liquid crystalline supramolecular semiconductors

Liquid crystalline behavior is found for supramolecular complexes with triphenylamine units at the periphery. The high hole transport values measured in the mesophase demonstrate a high potential as supramolecular semiconductors.

Synthesis of spirodithienogermole with triphenylamine units as a dopant-free hole-transporting material for perovskite solar cells

Spiro-condensed dithienogermoles with electron-donating aromatic substituents were prepared, one of which was examined as the hole-transporting material of perovskite solar cell, providing the maximal photo-current conversion efficiency of 14.67%.

Non-doped OLEDs based on tetraphenylethylene phenanthroimidazoles with negligible efficiency roll-off: effects of end group regulated stimulus responsive AIE luminogens

The positional isomers of phenanthroimidazoles, TPE-NPPB and TPE-APPB, have been designed to understand the positional effects of triphenylamine (TPA) and tetraphenylethylene (TPE) units on the aggregation-induced emission and mechanochromism.

A unique self-reporting photosensitizer enabling simultaneous photodynamic therapy and real-time monitoring of phototheranostic process in a dynamic dual-color mode.

Phototheranostics has attracted great interest in cancer therapy. Small-molecule self-reporting photosensitizers, one kind of idea agent in phototheranostics, enables simultaneous photodynamic therapy (PDT) and feedback of therapeutic efficacy. However, previous such photosensitizers exclusively employed the change of single emission to monitor cell death, which can be disturbed by variations in photosensitizer concentration and the excitation intensity. Herein, we report a unique self-reporting photosensitizer TPA-3PyA+ constructed from a twisted triphenylamine unit (TPA), three benzene ring units and three cyanovinyl-pyridinium units (PyA) for PDT and its real-time monitoring in a dynamic dual-color mode. TPA-3PyA+ possesses a rotatable electron donor-π bridge-electron acceptor framework and exhibits high singlet oxygen quantum yield (124%) and a twisted intramolecular charge transfer (TICT) effect. TPA-3PyA+ not only enables effective staining of cancer cells with dual-color fluorescence due to the TICT effect but also shows excellent PDT performance. The simultaneous change in emission color, intensity and intracellular location of TPA-3PyA+ during cell death allows it to self-report cell death. Moreover, the change of dual-emission color allows distinguishing living and dead cells and effectively avoids interference in previous single-emission self-reporting photosensitizers. This work highlights the great potential of a self-reporting photosensitizer with dual-color emissions for efficient feedback of theranostics.

Optimization of porphyrin dyes with a bulky triphenylamine donor for developing efficient dye-sensitized solar cells

To fabricate efficient dye-sensitized solar cells (DSSCs), three porphyrin dyes XW65−XW67 have been designed and synthesized using a bulky triphenylamine donor. Based on our previously reported dyes with a carbazole donor, a bulky triphenylamine unit was employed as the donor to synthesize XW65 with the aim to enhance the electron donating ability and suppress dye aggregation. As a result, XW65 shows enhanced photocurrent density (Jsc) and open circuit voltage (Voc), affording a high efficiency of 9.02%. On this basis, XW66 was synthesized with a methyl group introduced into the carboxyphenyl acceptor to further suppress dye aggregation and improve the Voc, achieving an enhanced efficiency of 9.23% with improved Voc of 849 mV and Jsc of 14.87 mA cm−2, which can be ascribed to the further suppressed dye aggregation and enhanced adsorption amount on the TiO2 film induced by the additional methyl group. To further improve the Jsc, a benzothiadiazole (BTD) unit has been introduced as the auxiliary acceptor to afford XW67, which exhibits a strikingly red-shifted monochromatic photon-to-electron conversion efficiency (IPCE) onset wavelength of 830 nm, obtaining the highest Jsc value of 15.83 mA cm−2 among the three dyes. Consequently, despite the sacrifice of Voc caused by the severe dye aggregation associated the extended conjugation framework, XW67 exhibits the highest efficiency of 9.43%. On this basis, cosensitization with WS-5 afforded elevated efficiencies of 10.07%, 10.38% and 10.13% for XW65−XW67, respectively, owing to the simultaneously enhanced Jsc and Voc. These results indicate that it is effective to develop efficient DSSCs based on cosensitization of optimized porphyrin dyes containing a bulky triphenylamine donor, a methyl group on the carboxyphenyl acceptor, and an auxiliary electron acceptor.

Characterization of α-phenyl-4′-(diphenylamino)stilbene single crystal and its anisotropic conductivity

Presently, organic-semiconductor electronics suffer from low performance owing to their amorphous nature. Improving their crystallinity, and thus the charge transport properties is a crucial endeavor. Accordingly, this study aims to elucidate the conductivity mechanism of a novel triphenylamine-derivative single crystal. We successfully synthesized an α-phenyl-4′-(diphenylamino)stilbene (TPA) single crystal via a solution method employing the solubility and supersolubility curves of TPA in the tetrahydrofuran (THF) solvent. Its crystal structure was determined via single-crystal X-ray diffraction (SCXRD), which revealed that the obtained single crystal contains not only TPA but also THF. The molecular ratio of TPA to THF was found to be 2:0.74. We further analyzed the hole transport property in three directions of the single crystal, and the anisotropic conductivity was observed. Based on the results of the observed molecular packing and charge transport property, we confirm that the observed anisotropic conductivity is determined based on the orientation of the triphenylamine unit in each direction of the TPA single crystal. Overall, the findings can help in guiding the design of high-mobility organic semiconductors for realizing more effective organic electronic devices.

Benzodithiophene-based small molecules with various termini as hole transporting materials in efficient planar perovskite solar cells

In this study we prepared four benzodithiophene (BDT)-based small organic molecules presenting bithiophene (TT), thiophene (FT), carbazole (CB), and triphenylamine (TPA) units, respectively, as termini, and used them as hole transporting materials for perovskite solar cells (PSCs). The high degrees of planarity of these BDT-based small molecules imparted them with high degrees of stacking and charge transport. These small molecules had suitable optical properties and energy level alignments for use in PSCs based on MAPbI 3 , with compact-TiO 2 as the electron transporting layer and a BDT-based material as the hole transporting layer, in a n–i–p structure. Among our tested BDT-based materials, the PSC incorporating BDT-TT had the best performance, with an average power conversion efficiency of 13.63%. The benzodithiophene (BDT) derivatives presenting bithiophene (TT), carbazole (CB), thiophene (FT), and triphenylamine (TPA) units based small molecules used them as hole transporting materials to fabricate planar perovskite solar cells. • We have prepared benzodithiophene (BDT) derivatives presenting bithiophene (TT), carbazole (CB), thiophene (FT), and triphenylamine (TPA) units and then used them as hole transporting materials to fabricate n–i–p PSCs. The power conversion efficiency of the device incorporating BDT-TT was the highest among our tested PSCs. • The film of the small molecule BDT-TT had the best morphology among our tested BDT-based HTMs, suggesting that TT units might be useful components when designing new hole transporting materials for high-performance PSCs. • Additives improved the performance of our PSCs by increasing the mobilities in the hole transporting materials, thereby achieving higher power conversion efficiencies.

A Bifunctional Bulky Thienothiophene Derivative; Synthesis, Electronic‐Optical Properties and OLED Applications

AbstractApplying thienothiophenes (TT) as a linker, a bulky bifunctional thienothiophene, TT‐TPA‐TPE3, possessing triphenylamine (TPA) and tetraphenylethylene (TPE) units, was designed, synthesized, and fully characterized. Its optical and electronic properties were explained by UV‐Vis spectroscopy, cyclic voltammetry (CV) and Aggregation‐Induced Emission (AIE) study. TT‐TPA‐TPE3 exhibited positive solvatochromism in the range of solvent polarities from DMF to toluene, displaying emissions from yellowish to bluish between 480–525 nm. Utilizing TT‐TPA‐TPE3 as a hole‐transporting layer, its organic light emitting devices (OLEDs) were fabricated and their performances were investigated. The synthesized emitter exhibited green and blue emissions in device applications. A mega Stoke's shift of 114 nm in THF and a large Stoke's shift of 78 nm on ITO were observed. A maximum luminance of 580 cd m−2 and a turn‐on voltage of 7.01 V were obtained, indicating that TT‐TPA‐TPE3 has a good hole‐transporting ability.

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.