Carbazole Groups Research Articles

High contrast stimuli-responsive fluorescence emitters based on carbazole-cyanostilbene derivatives with aggregation induced emission properties

Due to the aggregation induced emission (AIE) materials exhibiting obvious fluorescent emission changes under the external stimuli of heat, solvent, force and so on, significant efforts have been directed toward developing AIE-active materials with high contrast stimuli-responsive fluorescence behaviors. Herein, three electron-donor(D)-electron-acceptor(A) and D-A-D type organic fluorescence emitters of Cz-DC-tBu, Cz-DC-CN and Cz-DC-OMe were facilely synthesized using carbazole group as D unit and cyano group as A unit. They showed typical AIE features and exhibited remarkable color changes under mechanical force and in different polarity solvents, respectively. The stimuli-responsive mechanism of the compounds were investigated by powder X-ray Diffraction (PXRD) and density functional theory calculations (DFT), which revealed that the mechanofluorochromic behaviors were associated with the molecular packing modes, and the solvatochromic effects were caused by the intramolecular charge-transfer transition (ICT) effect. Significantly, it was found that Cz-DC-tBu showed high contrast stimuli-responsive behaviors through adjusting the substituent groups on the cyanostilbene unit with CN, OMe, and tBu groups, respectively. This study provided a new strategy for the design of AIE-active stimuli-responsive fluorescence emitters, and made them possible using in stress sensors, chemical detection, memory storage, anti-counterfeiting applications.

Efficient and Stable Inverted Perovskite Solar Cells Enabled by a Fullerene‐Based Hole Transport Molecule

AbstractDesigning an efficient modification molecule to mitigate non‐radiative recombination at the NiOx/perovskite interface and improve perovskite quality represents a challenging yet crucial endeavor for achieving high‐performance inverted perovskite solar cells (PSCs). Herein, we synthesized a novel fullerene‐based hole transport molecule, designated as FHTM, by integrating C60 with 12 carbazole‐based moieties, and applied it as a modification molecule at the NiOx/perovskite interface. The in situ self‐doping effect, triggered by electron transfer between carbazole‐based moiety and C60 within the FHTM molecule, along with the extended π conjugated moiety of carbazole groups, significantly enhances FHTM's hole mobility. Coupled with optimized energy level alignment and enhanced interface interactions, the FHTM significantly enhances hole extraction and transport in corresponding devices. Additionally, the introduced FHTM efficiently promotes homogeneous nucleation of perovskite, resulting in high‐quality perovskite films. These combined improvements led to the FHTM‐based PSCs yielding a champion efficiency of 25.58 % (Certified: 25.04 %), notably surpassing that of the control device (20.91 %). Furthermore, the unencapsulated device maintained 93 % of its initial efficiency after 1000 hours of maximum power point tracking under continuous one‐sun illumination. This study highlights the potential of functionalized fullerenes as hole transport materials, opening up new avenues for their application in the field of PSCs.

Original Blue Light-Emitting Diphenyl Sulfone Derivatives as Potential TADF Emitters for OLEDs

Organic light-emitting diodes (OLEDs) have emerged as one of the dominant technologies in displays due to their high emission efficiency and low power consumption. However, the development of blue color emitters has fallen behind that of red and green emitters, posing challenges in achieving optimal efficiency, stability, and accessibility. In this context, thermally activated delayed fluorescence (TADF) emitters hold promise as a potential solution for cost-effective, exceptionally efficient, and stable blue OLEDs due to their potential high efficiency and stability. TADF is a principle where certain organic materials can efficiently convert both singlet and triplet excitons, theoretically achieving up to 100% internal quantum efficiency. This research focused on diphenyl sulfone derivatives with carbazole groups as TADF compounds. Quantum chemical calculations and photoluminescence properties show the potential TADF properties of the molecules. New materials exhibit glass transition temperatures that would classify them as molecular glasses. Depending on the structure of the molecule, the photoluminescence emission is in the blue or green spectral region. Organic light-emitting diodes were fabricated from neat thin films of emitters by the wet casting method. The best performance in the deep blue emission region was achieved by a device with a turn-on voltage of 4 V and a maximum brightness of 178 cd/m2. In the blue-green emission region, the best performance was observed by an OLED with a turn-on voltage of 3.5 V, reaching a maximum brightness of 660 cd/m2.

Photoactive fluorenyl-functionalized polypropylene for high-performance dielectrics

Reducing the impact of polyolefins on the environment is a difficult task not only because of its ubiquity in everyday items, but also because these polymers are used on a massive scale as high-performance materials, for example in electronics and automotive applications. This is the case for polypropylene that behaves as a robust and efficient dielectric in capacitors as a result of its high melting temperature and very low dielectric dissipation factor. The current challenge is to increase its low permittivity, in order to improve energy density and, at the same time, to contribute to the reduction of production, thus progressively increasing the miniaturization of devices.Low content functionalisation has been found to be an efficient route to rise the polypropylene (PP) permittivity, without compromising the mechanical and thermal stability of the material. Recent work has shown that decreasing chain mobility in the amorphous phase is key to maintaining dielectric loss into the low level of PP. This has been achieved by inserting carbazole or N-alkyl pyrrole groups. The former increases the Tg due to their characteristic π-π stacking interactions and both enable tailored crosslinking, UV and thermally activated respectively.The present study analyses the synthesis and thermal and dielectric stabilities of poly-(propylene-co-9-(undec-10-en-1-yl)-9H-fluorene), with fluorene contents up to 3 mol%, as another example of PP grade that has both enhanced Tg and crosslinking potential under UV radiation. Initial results reveal that these materials have a relative permittivity (ɛr) up to 3 and dielectric losses under 0.005. As in the case of carbazole, the strong π-π stacking between fluorene units improves the thermal, mechanical and dielectric responses and also, that further improvement in stability would be possible under appropriate post-processing irradiation conditions.

A Self‐Assembling Molecule for Improving the Mobility in PEDOT:PSS Hole Transport Layer for Efficient Perovskite Light‐Emitting Diodes

AbstractPoly(3,4‐ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS), the most widely used hole injection layer (HIL) for perovskite light‐emitting diodes (PeLEDs), has a large hole injection energy barrier and easy charge separation at PEDOT:PSS/perovskite layer. Here, a self‐assembling molecule (SAM) called (2‐(3,6‐dimethoxy‐9H‐carbazol‐9‐yl)ethyl) phosphonic acid (MeO‐2PACz) is introduced as an interlayer between PEDOT:PSS and perovskite to overcome the limitations of PEDOT:PSS HIL. The MeO‐2PACz interlayer facilitated hole injection due to the reduced hole injection energy barrier and the improved hole mobility, enhanced photoluminescence (PL) due to the prevented charge transfer from perovskite into PEDOT:PSS, and reduced interface trap density due to the passivation of methoxy and carbazole group toward perovskite. As a result, PeLEDs with MeO‐2PACz interlayer has greatly enhanced maximum luminance (Lmax = 17,310 cd m−2) and reduced leakage current, resulting in higher maximum external quantum efficiency (EQEmax = 21.50%) compared to pristine Control device (EQEmax of 4.82%).

End Cap Effect on Solution-Processable Deep Blue Lasing Materials with Low-Amplified Spontaneous Emission Thresholds.

Organic lasers have attracted increasing attention owing to their superior characteristics such as lightweight, low-cost manufacturing, high mechanical flexibility, and high emission-wavelength tunability. Recent breakthroughs include electrically pumped organic laser diodes and an electrically driven organic laser, integrated with an organic light-emitting diode pumping. However, the availability of efficient deep blue organic laser chromophores remains limited. In this study, we develop two novel rigid oligophenylenes, end-capped with carbazole and phenylcarbazole groups, to demonstrate exceptional optical and amplified spontaneous emission (ASE) properties. These oligophenylenes are not only solution processable but also exhibit remarkably high solution photoluminescence quantum yields (PLQYs) of 90% and high radiative rates of 1.35 × 109 s-1 in the deep blue range. Our theoretical calculations confirm that the carbazole and phenylcarbazole end groups play a pivotal role in enhancing the optical transitions of the oligophenylene laser chromophores, thereby elevating their emission oscillator strengths. Remarkably, these materials demonstrate low solid-state ASE threshold values of 1.0 and 1.5 μJ/cm2 (at 431 and 418 nm, respectively). To the best of our knowledge, these ASE thresholds represent the lowest reported at these specific ASE wavelengths in the literature, regardless of whether they are solution-processed or thermally evaporated films. Furthermore, they exhibit excellent thermal and photostability, low triplet quantum yields, as well as negligible overlap of excited-state absorption within the ASE emission region, making them excellent candidates for a new class of deep blue materials for organic lasers. By integrating insights from theoretical calculations and experimental validation, our study provides a comprehensive understanding of the design principles behind these high-performing organic laser chromophores, paving the way for the development of advanced organic lasers with enhanced performance characteristics.

A versatile fluorescent probe for the ratiometric detection of hydrazine (N2H4) in water, soil, plant, and food samples

Hydrazine (N2H4) is a crucial chemical raw material extensively utilized in chemical production. However, due to its volatility, water solubility, and high toxicity, both the gaseous form and aqueous solution of N2H4 pose significant environmental risks by causing severe pollution that can adversely impact plants, microorganisms, and human health. Therefore, accurate detection of N2H4 in the environment is imperative for safeguarding public health. In this study, we synthesized a ratiometric fluorescent probe (BCaz-Cy2) based on Carbazole and Hemicyanine groups. This probe exhibits simple synthesis procedure, rapid response time, high sensitivity and selectivity as well as remarkable detection signals. It enables effective detection of N2H4 in various matrices such as water, food, soil and plant samples thereby significantly expanding the scope of applications for N2H4 probes.

Efficient and Stable Inverted Perovskite Solar Cells Enabled by a Fullerene-Based Hole Transport Molecule.

Designing an efficient modification molecule to mitigate non-radiative recombination at the NiOx/perovskite interface and improve perovskite quality represents a challenging yet crucial endeavor for achieving high-performance inverted perovskite solar cells (PSCs). Herein, we synthesized a novel fullerene-based hole transport molecule, designated as FHTM, by integrating C60 with 12 carbazole-based moieties, and applied it as a modification molecule at the NiOx/perovskite interface. The in-situ self-doping effect, triggered by electron transfer between carbazole-based moiety and C60 within the FHTM molecule, along with the extended π conjugated moiety of carbazole groups, significantly enhances FHTM's hole mobility. Coupled with optimized energy level alignment and enhanced interface interactions, the FHTM significantly enhances hole extraction and transport in corresponding devices. Additionally, the introduced FHTM efficiently promotes homogeneous nucleation of perovskite, resulting in high-quality perovskite films. These combined improvements led to the FHTM-based PSCs yielding a champion efficiency of 25.58% (Certified: 25.04%), notably surpassing that of the control device (20.91%). Furthermore, the unencapsulated device maintained 93% of its initial efficiency after 1000 hours of maximum power point tracking under continuous one-sun illumination. This study highlights the potential of functionalized fullerenes as hole transport materials, opening up new avenues for their application in the field of PSCs.

AIE-active large Stokes-shift BODIPY Functionalized with Carbazolyl for Lysosome-Targeted Imaging in Living Cells

A large number of studies have shown that lysosomal microcircumstances changes can affect many physiological and pathological processes at the cellular level. However, the visual detection of lysosomal microcircumstances is relatively difficult due to low pH (4.5–6.0) value in lysosomal that require the probe not only stable under acidic condition but also has a good localization effect to lysosomal. Obviously, novel fluorescent which possessed both acidic stability and lysosomal-target property together with lysosomal viscosity active is highly demanded. Herein, a novel BODIPY molecular CarBDP based on carbazole group was rationally designed and synthesized for the lysosomal imaging. CarBDP exhibited AIE feature with a large Stokes shift of up to 157 nm. More importantly, co-localization assay of the CarBDP-treated MCF-7 cells indicated that CarBDP has a good localization effect on lysosomal (Rr = 0.7109) due to the carbazole group while the normal BODIPY that without carbazole group (PhBDP) shows poor localization performance, this was the first time that a small molecule can locate lysosomes only based on carbazole group. CarBDP exhibits strong solid emission with long fluorescence decay lifetime (τ = 44.54 ns) and was stable under acid condition.The probe CarBDP assembled with carbazole group was successfully utilized for lysosomal localization and mapping lysosomal viscosity in live cells, which provides a novel candidate tool for the determination of lysosomal microcircumstances.

Molecular engineering of coumarins for enhanced 2-photon absorption property

Abstract A series of coumarin-based quadrupolar and octupolar derivatives containing electron-donating substituents (carbazole or diphenylamine groups) were synthesized. Their photophysical properties were explored in different organic solvents (toluene, dichloromethane, and dimethyl sulfoxide). Each donor group was connected via cyclic stilbene based on coumarin, resulting in compounds with large 2-photon absorption cross-sections.

Symmetry Molecular Design Strategy for Highly Efficient Blue Electroluminescence with Hot Exciton Mechanisms

AbstractEmitters with a hot exciton mechanism are regarded as one of the most promising candidates for organic light‐emitting diodes (OLEDs). In this study, a deep‐blue emitter with the hot exciton mechanism is reported, namely 2An‐PCz, by integrating a pair of carbazole groups with a 9,9′‐bi‐anthracene nucleus. Owing to the symmetric molecular architecture and intrinsic local excited state character, multiple high‐lying reverse intersystem cross (hRISC) channels and large overlaps of frontier molecular orbits (FMOs) can be formed, facilitating rapid hRISC processes as well as enhancement of radiative transition rates simultaneously. Combined with the strong luminescence properties brought by the unique X‐packing mode, a high photoluminescence quantum yield of 60.5% is achieved in the non‐doped state. Strikingly, non‐doped deep‐blue OLEDs exhibited a maximum external quantum efficiency (EQE) of 10.50% with minimal efficient roll‐off, which is one of the highest values for deep‐blue organic light‐emitting devices based on hot exciton emitters thus far. The magneto‐electroluminescence (MEL) experiment and transient electroluminescence measurements corroborated that both the high EQE and suppressed efficiency roll‐off are attributable to the rapid “hot exciton” channels.

Thermoplastic polyimide with good comprehensive performance based on carbazole groups and short flexible linkages

AbstractThermoplastic polyimides (TPIs) can meet the requirements of advanced electronic packaging such as flexible copper clad laminate (FCCL) applied under extreme conditions, attributed to their excellent thermal stability, mechanical properties, electrical insulation and chemical resistance. With the increasing demands for electronic devices, such as applications in high‐frequency communication, it is highly desirable to develop high‐performance TPI with good thermoplasticity, thermal stability, mechanical properties and dielectric properties. However, there is a trade‐off between thermoplasticity and other properties. Herein, we introduce an effective strategy to afford TPIs with good performance by copolymerization of a diamine monomer consisted of a coplanar aromatic carbazole group and a short flexible linkage methylene group. On the one hand, short flexible linkages help improve the flexibility of polymer chains and are not too much to enable small‐scale molecular motions below Tg. On the other hand, coplanar aromatic donor groups benefit to strong charge transfer complex (CTC) interaction and π‐π stacking interaction. Based on this strategy, the resultant TPI possesses good thermoplasticity with a proper Tg of 348 °C. Meanwhile, it preserves a low coefficient thermal expansion of 48 ppm K−1, low dielectric constant/dielectric loss factor of 3.27/0.0073 at 10 GHz, and tensile strength of ca. 78 MPa.

Carbazole-Based branched Poly(Aryl Piperidinium) membranes for Ultra-Stable anion exchange membrane fuel cells

In the technological development of anion exchange membrane fuel cells (AEMFCs), it is crucial to prepare anion exchange membranes (AEMs) with high conductivity and excellent dimensional stability. This study successfully developed highly branched poly(aryl piperidinium) AEMs by introducing 4,4′-bis(N-carbazolyl)-1,1′-biphenyl as branched linker unit into the poly(p-terphenyl piperidinium) backbone. With the introduction of the carbazole group, the plane-conjugated structure and non-rotatable properties are fully utilised, which effectively reduces the entanglement between the polymer backbones and increases the free volume of the AEMs, hence facilitates the construction of an efficient ion transport channel. The branched structure effectively reduces the water uptake of the membrane which leads to improved dimensional stability. The optimized QPCBP-TP-7 membrane exhibited high conductivity, reaching up to 151.88 mS cm−1 at 80 °C, along with excellent mechanical strength (TS = 42.51 MPa, EB = 13.32 %, wet state) and dimensional stability (SR of 22.9 % at 80 °C). Surprisingly, this membrane also exhibited favorable antioxidant properties (retaining over 97.28 % weight after 96 h in Fenton's reagent at 80 °C), and alkaline stability (retaining over 86.81 % efficacy after 1500 h in 5 M NaOH solution at 80 °C). In AEMFCs applications, the QPCBP-TP-7 membrane achieved peak power density (PPD) up to 616 mW cm−2 with the current density is 1330 mA cm−2 at 80 °C (H2-O2) and the QPCBP-TP-7 membrane remained stable and hardly degraded when operated at constant current of 0.1 A cm−2 (80 °C) over 100 h.

Electrochemical synthesis of donor-acceptor triazine based polymers with halochromic and electrochromic properties

Two triazine monomers substituted with aromatic α,β unsaturated ketones (chalcones) as connecting arms, holding triphenylamine or carbazole ending groups, were by the first time synthesized using commercial and inexpensive starting materials in just two steps. Triphenylamine and carbazole groups were strategically introduced in order to allow electrochemical polymerization and redox activity of the obtained films. The chalcone, together with the triphenylamine or carbazole outer groups, give rise to the formation of a donor-acceptor systems, allowing the generation of photoinduced intramolecular charge transfer (ICT) electronic transitions and providing basic sites for protonation. Because of the star-like chemical structure of the used triazine, electrochemical polymerization of these monomers conducted to the formation of hyperbranched structures. The polymeric materials exhibited not only electrochromic properties but also showed a halochromic behavior. Spectroelectrochemical studies of the films showed different colorations in the three redox states (neutral, semioxidized and fully oxidized). The color changes are fast and easily detected by the naked eye. Electrochemical parameters such as optical contrast, coloration efficiency, optical memory, and long-term stability for both films were obtained and compared. A quasi-solid window-type electrochromic device was assembled using the electrogenerated polymer with the best electrochromic performance and stability. Moreover, the triphenylamine based polymer showed reversible color changes upon acid-base vapor exposure cycles, demonstrating that this polymer can be used not only in electrochromic devices but also in acid vapor sensors.

A novel fluorescent probe based on carbazole-thiophene for the recognition of hypochlorite and its applications

A carbazole thiophene-aldehyde and 4-methylbenzenesulfonhydrazide conjugate CSH was synthesized by introducing 5-thiophene aldehyde at the 3-position of the carbazole group as the precursor and then condensing it with 4-methylbenzenesulfonhydrazide. CSH has high selectivity and sensitivity towards ClO−, which can specifically identify ClO− by UV–Vis and fluorescence spectroscopy. CSH can rapidly respond to ClO− in the physiological pH range through a fluorescence quenching pattern, accompanied by the color of CSH changing markedly from turquoise to yellowish green under the 365 nm UV light. Probe CSH exhibits a quantitative response to ClO− (0–11 μM) with a low detection limit (1.16 × 10−6 M). Cell imaging experiments have shown that CSH can capture fluorescent signals in the cyan and yellow channels of HeLa cells through fluorescence confocal microscopy, and can successfully identify exogenous ClO− in HeLa cells. In addition, probe CSH can also be used to detect ClO− in environmental water samples. These results indicate that CSH has potential application prospects in the environmental analysis and biological aspects.

Novel carbazole-based ionic liquids and their charge-transfer kinetics pertaining to Marcus theory towards highly efficient redox active electrolytes

Three novel redox ionic liquids (RILs) based on carbazole, incorporating imidazolium and bistriflimide (TFSI) groups, have been successfully synthesized and electrochemical properties comprehensively evaluated.

Efficient Silicon Solar Cells through Organic Self‐Assembled Monolayers as Electron Selective Contacts

AbstractEffective charge carrier‐selective contacts are a crucial component of high‐performance crystalline silicon (c‐Si) solar cells. Organic materials deposited via self‐assembly on the c‐Si surface are promising candidates for simplified, scalable, and cost‐effective processing of charge extraction layers. This study investigates the application of nPACz self‐assembled monolayers (SAMs), based on carbazole and phosphonic acid groups, where n (= 2, 4, or 6) is the aliphatic chain length, to facilitate electron extraction in c‐Si solar cells by tuning the work function of aluminum (Al) at the rear contact. So far, these SAM molecules are mainly applied as the hole‐selective layer in state‐of‐the‐art perovskite and organic solar cells, via anchoring on a metal oxide electrode. Here, by inserting 2PACz between amorphous silicon passivated c‐Si and Al, an electron‐selective contact with a contact resistivity of 65 mΩ cm2 is achieved and a power conversion efficiency of 21.4% with an open‐circuit voltage of 725 mV and a fill factor of 79.2% is demonstrated. Although the 2PACz displays some instability in this study, its initial performance is comparable to those achieved with conventionally used n‐type amorphous silicon. This study highlights the potential of solution‐processable organic SAMs in forming carrier‐selective contacts for c‐Si heterojunction solar cells.

Spectroscopic and computational characterization of new promising donors – Manganese(III) porphyrins bearing carbazole groups

UV–vis, IR, MALDI-TOF, and femtosecond transient absorption spectroscopic techniques together with DFT and TDDFT computations have been employed to explore new manganese(III) porphyrins bearing [3,6-di-tert-butyl-carbazol-9-yl-benzoyloxy]- (MnP1) and [3,6-bis(3΄,6΄-di(tert-butyl)-9΄H-carbazol)-9H-carbazolbenzoyloxy]phenyl (MnP2) groups. MnP1 and MnP2 demonstrate the significant deviation of the macrocycle from planarity, which can be due to the high spin (S = 2) state of the manganese(III). By studying MnP1 and MnP2 excited states, the formation of the trip-quintet ones decaying in 13.7 ps and 17.3 ps, respectively, was established. The comparisons of MnP1 and MnP2 with the Co and Zn analogs have shown that both the number of generations and metal ion influence excited-state dynamics and electronic/structural properties.

A design strategy of pure Type-I thiadiazolo[3,4-g]quinoxaline-based photosensitizers for photodynamic therapy

Most photosensitizers (PSs) for photodynamic therapy (PDT) can generate singlet oxygen through transferring energy with oxygen, called Type-II PSs. However, the microenvironment of solid tumor is usually anoxic. Type-I PSs can generate reactive oxygen species (ROS) through transferring electron to substrate, showing more efficient in PDT. But pure Type-I PSs are very rare. The relationship between PSs’ chemical structure and Type-I mechanism has not been explicitly stated. In this study, two thiadiazolo [3,4-g]quinoxaline (TQ) PSs (PsCBz-1 and PsCBz-2) are synthesized through introducing carbazole groups to the 4,9-position of TQ backbone. Comparing with their prototype PS, 4,9-dibrominated TQ (TQs-4), the introduction of carbazole groups reverses the reaction mechanism of PSs from pure Type-II to pure Type-I. Excitingly, the water-dispersible nanoparticles (NPs) of PsCBz-1 can achieve strong phototoxicity in vitro under both normoxia and hypoxia through Type-I mechanism. In addition, PsCBz-1 NPs also exhibits remarkable PDT antitumor effect in vivo. This study provides a feasible design strategy for pure Type-I PSs.

Self-Standing Porous Aromatic Framework Electrodes for Efficient Electrochemical Uranium Extraction.

Electrochemical uranium extraction from seawater provides a new opportunity for a sustainable supply of nuclear fuel. However, there is still room for studying flexible electrode materials in this field. Herein, we construct amidoxime group modified porous aromatic frameworks (PAF-144-AO) on flexible carbon cloths in situ using an easy to scale-up electropolymerization method followed by postdecoration to fabricate the self-standing, binder-free, metal-free electrodes (PAF-E). Based on the architectural design, adsorption sites (amidoxime groups) and catalytic sites (carbazole groups) are integrated into PAF-144-AO. Under the action of an alternating electric field, uranyl ions are selectively captured by PAN-E and subsequently transformed into Na2O(UO3·H2O)x precipitates in the presence of Na+ via reversible electron transfer, with an extraction capacity of 12.6 mg g-1 over 24 days from natural seawater. This adsorption-electrocatalysis mechanism is also demonstrated at the molecular level by ex situ spectroscopy. Our work offers an effective approach to designing flexible porous organic polymer electrodes, which hold great potential in the field of electrochemical uranium extraction from seawater.