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Due to their distinctive intrinsic advantages, the nanoaggregates of conjugated polyelectrolytes (CPEs) are fascinating and attractive for various luminescence applications. Generally, the emission luminescence of CPEs is determined by the conjugated backbone structure, i.e., different conjugated backbones of CPEs produce emission luminescence with different emission wavelength bands. Here, we polymerized the bis(boronic ester) of benzothiadiazole and an alkyl sulfonate sodium-substituted dibromobenzothiatriazole to provide PBTBTz-SO3Na with different molecular weights via controlling the ratio of the monomer and the catalyst. Theoretically, the CPEs with the same molecular structure usually display similar photoelectronic performances. However, the resulting PBTBTz-SO3Na reveal a similar light absorption property, but different luminescence. The higher molecular weight is, the stronger the fluorescence intensity of PBTBTz-SO3Na that occurs. PBTBTz-SO3Na with different molecular weights have different colors of luminescence. It is well known that the molecular aggregates often led to weaker luminescent properties for most of the conjugated polymers. However, PBTBTz-SO3Na exhibits a higher molecular weight with an increasing molecular chain aggregation, i.e., the nanoaggregates of PBTBTz-SO3Na are beneficial to emission luminescence. This work provides a new possible chemical design of CPEs with a controllable, variable luminescence for further optoelectronics and biomedicine applications.

Photocatalytic hydrogen evolution from water has recently drawn tremendous attention and stimulated extensive efforts in the design of high-performance photocatalysts. Here, we designed a series of...

The associative phase separation of water-soluble polyelectrolytes is important across many different fields including food science, biomedicine, materials science, and prebiotic organization. Spec...

Robust photosensitizers with strong red/NIR fluorescence, efficient reactive oxygen species (ROS) generation and high photostability are highly desired for photodynamic therapy (PDT). Herein, three novel red conjugated polyelectrolytes (CPEs) with tetraphenylethene and 2,1,3-benzothiadiazole on the main chains and triphenylphosphonium on the side chains are developed. These CPEs display apparent aggregation-induced emission feature and high fluorescence quantum yields in the aggregated state. They can target lysosome in HeLa cells for fluorescence bioimaging. By virtue of the good retention effect and high photostability, these CPEs show ultralong-term tracing performance of subcutaneous tumors, and the tumor site can still be visualized for 20 days after injection. Owing to their good biocompatibility and strong ROS generation ability, the image-guided PDT based on these CPEs can effectively inhibit the growth of subcutaneous tumor and significantly prolong the survival of tumor bearing mice. The H&E and IHC staining reveal that the PDT of these CPEs depress the proliferation of tumor cells, and promote apoptosis and necrosis process. These new CPEs may be employed both as fluorescent probes for in vitro and in vivo long-term tracing and as photosensitizers for image-guided PDT of tumors.

Conjugated polyelectrolytes prepared from carbon–carbon coupling polymerization have difficulties in controlling the precision molecular weight (Mn), so that the effect of Mn on their performance r...

Colloidal semiconductor nanocrystals (NCs) and, recently, nanoplatelets (NPLs), owing to their efficient and narrow-band luminescence, are considered as frontier materials for light-emitting diode (LED) technology. NC-LEDs typically incorporate interfacial layers as charge regulators to ensure charge balancing and high performance. In this Letter, we show the prolongation of the lifetime of multilayer solution-processed NC-LEDs by combining a self-doped conductive conjugated polyelectrolyte and exfoliated molybdenum disulfide (MoS2) flakes as an alternative to PEDOT:PSS. The ink features a neutral pH and a tunable hydrophobicity that mainly results in a remarkable stability of LEDs, using CdSe/CdZnS NPLs.

We report a Forster resonance energy transfer (FRET)-based imaging ensemble for the visualization of membrane potential in living cells. A water-soluble poly(fluorene-cophenylene) conjugated polyelectrolyte (FsPFc10) serves as a FRET donor to a voltage-sensitive dye acceptor (FluoVolt™ ). We observe FRET between FsPFc10 and FluoVolt™ , where the enhancement in FRET-sensitized emission from FluoVolt™ is measured at various donor/acceptor ratios. At a donor/acceptor ratio of 1, the excitation of FluoVolt™ in a FRET configuration results in a three-fold enhancement in its fluorescence emission (compared to when it is excited directly). FsPFc10 efficiently labels the plasma membrane of HEK 293T/17 cells and remains resident with minimal cellular internalization for ~ 1.5 h. The successful plasma membrane-associated colabeling of the cells with the FsPFc10-FluoVolt™ donor-acceptor pair is confirmed by dual-channel confocal imaging. Importantly, cells labeled with FsPFc10 show excellent cellular viability with no adverse effect on cell membrane depolarization. During depolarization of membrane potential, HEK 293T/17 cells labeled with the donor-acceptor FRET pair exhibit a greater fluorescence response in FluoVolt™ emission relative to when FluoVolt™ is used as the sole imaging probe. These results demonstrate the conjugated polyelectrolyte to be a new class of membrane labeling fluorophore for use in voltage sensing schemes.

We demonstrate a series of direct arylation polycondensed conjugated polyelectrolytes (CPEs) for application in universal and thickness-insensitive electron transport materials (ETMs) of highly efficient polymer solar cells (PSCs). The energy levels, absorption spectra, and self-doping behaviors of these CPEs are altered by the substituted alkyl and alkoxy ammonium side chains. PSCs with three donor:acceptor combinations as active layers are examined and the results indicate that these CPEs are capable of achieving high efficiency for both fullerene PSCs and non-fullerene PSCs. The excellent capability of CPEs for interface modification achieves high-performance PM6:Y6-based PSCs with a PCE of over 16%. Moreover, the high electron mobilities of these CPEs endow them with high performance at thicknesses ranging from 10 nm to 100 nm, indicating that these CPEs are good candidates as universal and thickness-insensitive ETMs for PSCs.

Crosslinking of semiconductors is critical towards building heterostructures to enable flexibility in the design of devices. Bis(fluorophenyl azide)s (FPAs) and their sterically-substituted derivatives (sFPAs) have been demonstrated to be able to photo-crosslink semiconductor polymers upon deep-UV exposure, stabilizing their morphologies in devices. Here, we report the development of both UV (254 nm) and i-line (365 nm) photo-activatable FPA and sFPA – FPA80 and sFPA82 – both incorporating 3,5-bis(methylene)-1,1-dimethyl-4-piperidonium, a conjugation-extending bridge that also bears an ionic group. These materials are useful for generic photo-crosslinking of both conjugated and non-conjugated polyelectrolytes. Good thermal stability and solubility in polar organic solvents are obtained. Good film retention (>80%) can be achieved with a crosslinker loading of less than 10 wt/wt% for high-molecular polymers (Mw > 100k), superior to alkyl bisazides. The photo-crosslinking efficiency of ca. 20% in model polyelectrolytes is limited by the occlusion of ionic crosslinkers from the polymer matrix where the C–H insertion reaction occurs, hence suppressing photo-crosslinking efficiency.

Conjugated polyelectrolytes (CPEs) have developed as promising hole transport materials for perovskite solar cells (PSCs). The conjugated backbone serves as an efficient vehicle for transporting holes, and the electric dipole layer formed through the organization of ionic groups on CPEs may improve the hole collection efficiency. In this work, three CPEs anchored with –N(CH3)3+, –SO3− and –NH3+ ions, denoted as BF-NMe3, BF-SO3 and BF-NH3, respectively, were synthesized and applied as the hole transport material (HTM) of inverted planar PSCs. Replacing the benchmark material, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS), with the three CPEs as the HTM considerably improves the photovoltaic performance of PSCs. The results from scanning electron microscope imaging, X-ray diffraction and time-resolved photoluminescence indicate that the structure of the ionic species rather than the type of charge has a decisive impact on the perovskite morphology. Both cationic BF-NH3 and anionic BF-SO3 layers enable methylammonium lead iodide (MAPbI3) to grow into larger crystals and grains with fewer defects. Moreover, the electrochemical impedance spectroscopy measurements demonstrate that the BF-NH3 and BF-SO3 devices have comparable charge recombination resistance, which is apparently higher than that of the BF-NMe3 and PEDOT:PSS devices. Consequently, the cationic BF-NH3 can act as an excellent HTM as the anionic BF-SO3 and the champion cell based on BF-NH3 exhibits a superior power conversion efficiency of 17.7%.

In this work, an anionic conjugated polyelectrolyte (PCP-SO3K), in which the backbone contains alternating 4,4-bis-alkyl-4H-cyclopenta-[2,1-b;3,4-b']-dithiophene and benzene structural units and the charges are provided by pendant sulfonate groups, was synthesized. The ionic nature of PCP-SO3K renders it soluble in water, and PCP-SO3K aqueous solution exhibits good photostability, with two main absorbance bands centered at 490 nm and 837 nm before and after laser irradiation. Its NIR absorption in water, negligible photoluminescence and insignificant intersystem crossing endow PCP-SO3K with efficient photothermal therapy performance, and an effective photothermal conversion efficiency of 56.7% was realized. Thus, PCP-SO3K aqueous solution can be used as an effective photothermal agent for in vivo applications as its photoactivity can be triggered by NIR light and can convert laser energy into thermal energy in a water environment. Of particular importance is the fact that complete tumor remission without recurrence in 4T1 tumor-bearing mice was realized after intravenous injection of PCP-SO3K aqueous solution and laser irradiation (2.0 W cm-2, 808 nm). The results indicate that the application of anionic conjugated polyelectrolytes as photothermal agents in photothermal therapy provides a new platform for the design of photothermal agents for clinical cancer treatment.

This article provides an elaborate discussion of reports involving the development of latent fingerprints (LFPs) over the past decades with specific emphasis on the contribution of conjugated polymers (CPs) in the field of forensic science. CPs have been explored in the field of interdisciplinary sciences due to their widespread applications in the fields of imaging, chemical and biological sensors, electronic device, cancer therapeutics, etc. Even in the field of forensic sciences, these CP materials are in a continuous race with the existing technology and newer materials for the detection of fingerprint marks on various surfaces thus assisting in the unravelling of the precise identification of an individual suspect in modern criminology. Due to their excellent photophysical and chemical properties such as low toxicity, ease of functionalization, strong fluorescence emission, high quantum yield, and good optical stability, these CPs can lead to high resolution, and increased sensitivity and selectivity in the imaging of LFPs compared to those developed by traditional tedious methods. In this perspective, the challenges faced for LFP development and the role of various CPs including conjugated polyelectrolytes, polymer dots, and polymer nanoparticles are elaborately explained, thus, providing a systematic overview on techniques based on CPs as contrasting agents in the development of LFPs on various porous and nonporous substrates. There are various challenges pertaining to the development of LFPs on a multitude of surfaces which can be addressed by exploring materials with a suitable hydrophobic–hydrophilic balance and a receptor site for specific interactions with fingerprint components. The incorporation of this design principle has successfully led to the development of efficient platforms for rapid, onsite, intricate and unique LFP patterns on every kind of surface.

The interaction between ionic moieties and the electronic properties of organic and hybrid semiconductors can yield a variety of interesting and sometimes surprising effects. Ionic moieties can induce interface dipoles, support electrochemical doping and lead to band-bending. The dynamic motion of ions under electric fields and the induced changes in conductivity can make it difficult to de-convolute the various mechanisms at play. This review attempts to provide a perspective on different types of interactions between ions and semiconductors and goes into depth addressing the application of solution-processed polyelectrolyte and oligoelectrolyte materials to control the energy band structures and behaviour of organic and hybrid semiconducting optoelectronic devices. This review introduces and highlights different types of ionic materials (such as conjugated polyelectrolytes and molecular ionic dopants) that have been used to achieve different effects (such as creating interfacial dipoles, vacuum energy shifts, changes in Fermi energies and doping) in organic and hybrid semiconducting devices before going into greater depth with the emerging class of non-conjugated polyelectrolytes and oligoelectrolytes and provides a comprehensive summary of recent progress using these materials in semiconducting devices. This class of materials has been receiving increasing attention recently and provides insights into the fundamental effects of ionic functionalities on the energy band structures and functions in organic and hybrid semiconductors.

The photodetection properties of near-infrared quantum-dot photodetectors (NIR-QPDs) have been significantly improved by introducing novel cationic conjugated polyelectrolytes (CCPs) on ZnO. The formation of a quaternary ammonium salt at the end of the pendant groups of the CCPs generates a permanent dipole moment on the ZnO surface and effectively modifies the work function of ZnO, improving the charge transport at the interfaces between the ZnO and QD layers. The cationic charge density and the geometrical structures of CCP1–3 had crucial effects in determining the photo-responsivity (R) and detectivity (D*) of the NIR-QPDs. The higher cationic charge density of CCP2 improved the electron accepting properties of ZnO, resulting in 1.6–5.1-fold increased R values under 940 nm IR irradiation (0.1 mW cm−2, −1 V) compared to the ZnO-, ZnO/CCP1-, and ZnO/CCP3-based devices. Notably, the horizontally-aligned backbone of CCP2 toward the substrate gives a uniform film surface and insulating layer on ZnO, which improved the charge transport and maintained a relatively low and constant dark current under negative bias. As a result, D* of the CCP2-treated NIR-QPDs was increased by up to 1880% compared to the pristine ZnO-based devices, and by 200–250% compared to the CCP1- and CCP3-based devices.

Conjugated polyelectrolytes (CPEs) are a promising class of materials for photovoltaic and sensing applications due to their ability to undergo efficient photoinduced electron transfer (ET). Although water-soluble poly(p-phenylene ethynylene) (PPE) polyelectrolytes have been synthesized for various applications, no reports have clearly revealed the dynamics of the photoinduced ET process and charge transfer state of PPE-type CPE/electron acceptor systems. Herein, we investigated photoinduced ET from a water-soluble PPE based CPE functionalized with alkyl sulfonate (R–SO3−) as side groups to three cationic electron acceptors. Steady-state absorption studies showed a bathochromic shift of the absorption band for all CPE/acceptor mixtures compared to CPE as a result of the suppression of the conformational changes in the polymer caused by the ion–pair interaction. Stern–Volmer (SV) fluorescence quenching studies revealed that all of the cationic electron acceptors efficiently quenched the fluorescence of CPE with SV constants (KSV) in excess of 106 M−1. Picosecond transient absorption (TA) studies of a CPE/methyl viologen mixture revealed the absorption feature of the cation radical state (CPE˙+) of the polyelectrolyte. Kinetic measurements established that the forward electron transfer in the polyelectrolyte/acceptor mixtures occurs with rate constant kf > 1 × 1012 s−1 and the return ET occurs with kb = 3 × 1011 s−1. We also demonstrated that the electron transfer between a PPE-type polyelectrolyte and an acceptor in their assemblies could be modulated by a supramolecular approach, which revealed that the nature of the acceptor–supramolecule host–guest complexes dictates the kinetics of the electron transfer process.

Cationic conjugated polyelectrolytes can absorb negatively charged small interfering RNA (siRNA) and also visualize the cellular internalization of siRNA, which thus have been extensively explored as siRNA carriers. However, their low charge density cannot afford a high carrying capability, severely impeding gene transfection efficiency. Moreover, the intracellular controlled release of siRNA is another factor that limits the widespread use of siRNA therapeutics. Herein, we present a novel two-photon-induced charge-variable conjugated polyelectrolyte brush as an efficient siRNA carrier. This cationic conjugated polyelectrolyte brush (PPENBr-ONB) with densely cationic charges produces remarkable carrying capability with siRNA. In addition, PPENBr-ONB with large two-photon absorption (TPA) cross-section represents effective fluorescence resonance energy transfer (FRET) to photoresponsive side chain with 720 nm illumination for two-photon-induced photolysis. Hence, the charge transformation of the photoresponsive side chain from cations to zwitterions would remarkably elevate siRNA release. The obtained PPENBr-ONB shows considerable fluorescence quantum yields (0.16) in aqueous solution, sufficient to serve as a reporter for cellular imaging. Agarose gel electrophoresis experiments indicate that PPENBr-ONB exhibit excellent siRNA-loading capacity (1 mol PPENBr-ONB to more than 20 mol siRNA). Furthermore, PPENBr-ONB with large TPA cross-section (1.47 × 10

Polymeric photocatalysts for water splitting have received extensive attention recently. However, most polymeric photocatalysts suffer from an unexceptional hydrogen/oxygen evolution rate, primaril...

π-Conjugated polyelectrolytes (CPEs) have been studied as interlayers on top of a separate hole transport layer (HTL) to improve the wetting, interfacial defect passivation, and crystal growth of perovskites. However, very few CPE-based HTLs have been reported without rational molecular design as ideal HTLs for perovskite solar cells (PeSCs). In this study, the authors synthesize a triphenylamine-based anionic CPE (TPAFS-TMA) as an HTL for p-i-n-type PeSCs. TPAFS-TMA has appropriate frontier molecular orbital (FMO) levels similar to those of the commonly used poly(bis(4-phenyl)-2,4,6-trimethylphenylamine) (PTAA) HTL. The ionic and semiconducting TPAFS-TMA shows high compatibility, high transmittance, appropriate FMO energy levels for hole extraction and electron blocking, as well as defect passivating properties, which are confirmed using various optical and electrical analyses. Thus, the PeSC with the TPAFS-TMA HTL exhibits the best power conversion efficiency (PCE) of 20.86%, which is better than that of the PTAA-based device (PCE of 19.97%). In addition, it exhibits negligible device-to-device variations in its photovoltaic performance, contrary to the device with PTAA. Finally, a large-area PeSC (1 cm2 ) and mini-module (3 cm2 ), showing PCEs of 19.46% and 18.41%, respectively, are successfully fabricated. The newly synthesized TPAFS-TMA may suggest its great potential as an HTL for large-area PeSCs.

Organic electrochemical transistors (OECTs) have been demonstrated in a wide range of applications such as analyte detection, neural interfacing, impedance sensing and neuromorphic computing. Majority of OECTs use PEDOT:PSS and liquid electrolytes. In this talk, I will discuss the development of biomaterials as solid state electrolytes and conjugated polyelectrolytes (CPEs) as semiconductors for OECTs. The biogels that consist of gelatin and glycerol with high ionic conductivity are used as solid electrolytes. We establish a relation between morphology and protonic-conductivity of the gels, allowing for the fabrication of gel-based OECTs with desirable functionalities, good ON/OFF ratio and transconductance, fast-switching speed, and good stability in ambient air. Anionic CPEs are used as mixed conductor materials for OECTs to replace PEDOT:PSS. CPE-based OECTs operate in the accumulation mode, which allows for much lower energy consumption in comparison to commonly used depletion mode PEDOT:PSS devices. The physical and electrical properties of CPE-K have been fully characterized to allow a direct comparison to other top performing OECT materials. CPE-K demonstrates an electrical performance that is among the best that have been reported in the literature for OECT materials.

Halide-based perovskite materials have been spotlighted in light-emitting diodes and perovskite solar cells applications due to their excellent optical and electrical characteristics. In particular, excellent film quality of perovskite with defect passivation is required to obtain highly efficient and stable perovskite optoelectronic devices. However, lots of undesired trap sites by defect sites such as voids, pinholes, grain boundaries and under-coordinated ions in surface of film can be formed in solution-processed perovskite films, reducing the device performance and operational stability of perovskite devices. Here, we demonstrate efficient perovskite optoelectronic devices by incorporating poly(fluorene-phenylene)-based anionic conjugated polyelectrolytes (CPEs).

Conjugated polyelectrolytes (CPEs), comprised of conjugated backbones and pendant ionic functionalities, are versatile organic materials with diverse applications. However, the myriad of possible molecular structures of CPEs render traditional, trial-and-error materials discovery strategy impractical. Here, we tackle this problem using a data-centric approach by incorporating machine learning with high-throughput first-principles calculations. We systematically examine how key materials properties depend on individual structural components of CPEs and from which the structure–property relationships are established. By means of machine learning, we uncover structural features crucial to the CPE properties, and these features are then used as descriptors in the machine learning to predict the properties of unknown CPEs. Lastly, we discover promising CPEs as hole transport materials in halide perovskite-based optoelectronic devices and as photocatalysts for water splitting. Our work could accelerate the discovery of CPEs for optoelectronic and photocatalytic applications.

The synthesis of conjugated polymers with ionic substituents directly bound to their main chain repeat units is a strategy for generating strongly electron-accepting conjugated polyelectrolytes, as demonstrated through the synthesis of a series of ionic azaquinodimethane (iAQM) compounds. The introduction of cationic substituents onto the quinoidal para-azaquinodimethane (AQM) core gives rise to a strongly electron-accepting building block, which can be employed in the synthesis of ionic small molecules and conjugated polyelectrolytes (CPEs). Electrochemical measurements alongside theoretical calculations indicate notably low-lying LUMO values for the iAQMs. The optical band gaps measured for these compounds are highly tunable based on structure, ranging from 2.30 eV in small molecules down to 1.22 eV in polymers. The iAQM small molecules and CPEs showcase the band gap reduction effects of combining the donor-acceptor strategy with the bond-length alternation reduction strategy. As a demonstration of their utility, the iAQM CPEs so generated were used as active agents in photothermal therapy.

Battery electrodes are complex mesoscale systems comprising an active material, conductive agent, current collector, and polymeric binder. Although significant research on composite electrode materials for Li-ion batteries focuses on the design, synthesis, and characterization of the active particles, the binder component has been shown to critically impact stability and ensure electrode integrity during volume changes induced upon cycling. Herein, we explore the ability of water-soluble, carboxylated conjugated polymer binders to aid in electron and ion transport in magnetite-based anodes. Specifically, poly[3-(potassium-4-butanoate)thiophene] (PPBT) and a potassium carboxylate functionalized 3,4-propylenedioxythiophene (ProDOT)-based copolymer (WS-PE2) were investigated and evaluated against the control, potassium salt form of poly(acrylic acid) (PAA-K). When used in conjunction with a polyethylene glycol (PEG) surface coating for the magnetite active material, PPBT provided for overall improved electro...

The delocalization of electrons in conjugated polymers impacts their chain shape, affecting their local ordering, self-assembly, and ultimately charge transport. Conjugated polyelectrolytes introduce electrostatic interactions as a molecular design parameter to potentially tune chain rigidity by combining the π-conjugated polymer backbone with pendant ionic groups. In conventional polyelectrolytes, the self-repulsion of the bound charges induce extended rod-like chain configurations. Here, we leverage small-angle neutron scattering to measure the chain shapes of model conjugated polymers in dilute solution with controlled fractions of randomly distributed pendant charges. We find these model polythiophenes are semiflexible, with a persistence length of approximately 3 nm, regardless of charge fraction, suggesting the effective absence of electrostatic rigidity in conjugated polyelectrolytes. While the overall persistence length is negligibly impacted by pendant charges, optical spectroscopy indicates that the pendant charges increase the backbone torsion between thiophene rings without significantly impacting the π-conjugation length (the length of electron delocalization along a nearly planar backbone) in dilute solution. These results indicate the effective decoupling of the pendant ionic charges from the overall chain conformation with implications for solution processing of organic semiconductors.

Conjugated polyelectrolytes based on benzotriazole (BT) and benzothiadiazole (BTz) alt unit with a pendant sulfonate ion but different countercations were synthesized and named PBTBTz-SO3Na and PBTBTz-SO3TBA. PBTBTz-SO3Na was used as a cathode interface applied to polymer solar cells (PSCs), and ITO/PEDOT:PSS/active layer/cathode interlayer/Al was set as a device structure. The PSCs displayed an average power conversion efficiency (PCE) of 7.7%, revealing an unchanged efficiency in comparison with that of the control device fabricated from a CH3OH interlayer. TBA+, a different counteraction, was used instead of Na+ to further study the influence of counterions on the electrical property of PBTBTz-SO3−. PBTBTz-SO3TBA was used as a cathode interface to fabricate two types of PSCs based on PTB7:PC71BM and PBDB-T:ITIC, and their improved average PCEs were 8.6% and 9.1%, respectively.

Organic semiconductors for photocatalytic application have received wide attention recently. However, developing organic photocatalysts for highly efficient photocatalytic hydrogen evolution is a great challenge. Herein, we show highly efficient photocatalytic hydrogen evolution from a series of novel conjugated polyelectrolytes (CPEs) by modulating their interaction with co-catalysts. The water-soluble CPEs greatly enhance the photocatalytic performance with 50-fold improvement over that of their non-dissolved precursor conjugated polymer. More importantly, the photocatalytic activity of these CPEs can be optimized by regulating their interaction with Pt co-catalysts through molecular engineering on the side chain species and counterions of CPEs. The cationic CPEs perform better than anionic CPEs due to the robust interaction between quaternary ammonium side chains in cationic CPEs and Pt co-catalysts. It is found that the optimized interface contact between cationic CPEs and Pt co-catalysts can result in more efficient charge transfer and higher photocatalytic activity.

Manufacturing large-area devices through a low-cost and large batch printing technique is the key to the commercialization of organic solar cells (OSCs). However, the lack of printable anode interlayer (AIL) materials severely impedes the development of high-efficiency printed OSCs. Herein, we synthesize three p-type self-doped conjugated polyelectrolytes (CPEs), namely, PCP-B, PCP-2B, and PCP-3B, as printable AIL materials for fabricating high-performance and large-area OSCs. By increasing the number of benzene units in the polymer backbone, the work function of the CPEs was enhanced from 4.57 to 5.01 eV, and the optical transparency was also improved because of the enlarged polymer band gap. The improved photoelectronic properties as well as a good film-forming capacity make the PCP-3B an ideal AIL material to be processed by the printing technique. By using PCP-3B, a 1 cm2 printed device was fabricated in which all the functional layers, including the AIL, active layer, and cathode interlayer were processed by blade-coating, achieving a power conversion efficiency (PCE) of 9.67%. The PCE belongs to the highest efficiency at present for printable large-area OSCs, showing a promising prospect for the OSC mass production.

This study examines the use of Pd(0)-catalyzed chain-growth Sonogashira coupling to prepare a series of poly(phenylene ethynylene) (PPE)-type conjugated polyelectrolytes that feature alkyl sulfonat...

Polyfluorene-based conjugated polyelectrolytes as efficient cathode buffer layers have powerfully improved the device performance of polymer solar cells, but the p-type nature of backbones make them work efficiently only in very thin film (2∼5 nm). In this work, three new polyfluorene-based conjugated polyelectrolytes with self-doping effect, namely poly[(9,9-bis(6′-N,N,N-trimethylammoniumbromide)hexyl)fluorene-alt-(5,6-difluoro-4,7-di(thiophen-2-yl)benzo[c] [1,2,5]thiadiazole)] (PFTBT-NBr), poly[(9,9-bis(6′-N,N,N-trimethylammoniumbromide)hexyl)fluorene-alt-2,5-bis(2-octyldodecyl)-3,6-bis(thiophen-2-yl)-pyrrolo [3,4-c]pyrrole-1,4-dione (PFTDPP-NBr) and poly[(9,9-bis(6′-N,N,N-trimethylammoniumbromide)hexyl)fluorene-alt-N,N′-bis(2-decyltetradecyl)-1,7-bis(thien-2-yl)-perylene-3,4:9,10-tetracarboxylic-diimide (PFTPDI-NBr) are designed and synthesized as buffer layer for PSCs. These conjugated polyelectrolytes have the same polar side chains, but differ in the conjugated backbones which are composed of fluorene alternated with different electron-withdrawing group, benzothiadiazole (BT), diketopyrrolopyrrole (DPP) and perylenediimide (PDI) respectively. The n-type polarity of the conjugated backbones is found to be substantially strengthened by varying the electron affinity and conjugated planarity of these backbones. As a result, employing these conjugated polyelectrolytes as cathode buffer layers for PSCs can effectively boost the device performance. Notably, an excellent thickness tolerance (∼30 nm) of polyfluorene-based polyelectrolytes, especially for PFTPDI-NBr, is achieved in the PSCs, originating from the higher electron mobility and conductivity, better interface contact between active layer and electrode, and favorable morphology of active layer.

An eco-friendly n-type water/alcohol-soluble conjugated polyelectrolyte PFEO SO3 Li was synthesized and applied as a cathode interfacial layer in organic solar cells. The π-delocalized polyfluorene backbone has an intimate connection with the hydrophobic active layer, and the side chain with lithium ion may move toward the ZnO layer through the self-assembly property of conjugated polyelectrolytes. UV photoelectron spectroscopy indicated that modification with PFEO SO3 Li dramatically lowers the work function of indium-doped tin oxide (ITO)/ZnO and may form strong interfacial dipoles between ZnO and the active layer. Meanwhile, introduction of lithium ions as spectator cations may contribute to reduction of the intrinsic surface defects of ZnO. The green emission in the photoluminescence spectrum of ZnO disappeared after modification with PFEO SO3 Li. In addition, the roughness of ZnO barely changed after coating with PFEO SO3 Li, and the surface became more hydrophobic, which demonstrates that the thin conjugated polyelectrolyte layer exhibits good adhesion with both ZnO and the active layer. These phenomena indicate that the introduction of PFEO SO3 Li makes ITO/ZnO an efficient cathode. As a result, inverted organic solar cell devices with ZnO/PFEO SO3 Li double-interlayers exhibit high efficiencies of 11.7 and 10.6 % for PBDB-T:IT-M and PBDB-T:ITIC blend systems, respectively.

Conjugated polyelectrolytes (CPEs) have been successfully applied in organic photovoltaics and organic light-emitting diodes, and recently those with inorganic cations became to serve as a hole-transporting layer (HTL) in inverted perovskite solar cells (iPSCs), whereas the CPE HTL materials with organic cations are really limited. In this work, we design a CPE whose side-chains are end-capped by CH3NH3+ cations, the same cations as that in the perovskite layer. The CPE is found to be more compatible to the perovskite material, and shows stronger abilities to reduce the traps both at the surface and in the bulk of the perovskite layer, compared with the typical poly(3,4-ethylenedioxythiophene): poly(styrenesulfonate) (PEDOT:PSS). The resulting iPSC presents much improved photovoltaic properties and a better long-term stability, with a power conversion efficiency of 19.76%, which is the highest value ever reported for iPSCs based on CPE HTLs.

Polar semiconducting polymers based on a conjugated polymer backbone endowed with chemically anchored polar groups on the side chains have proved to be particularly interesting as optimization layer at organic/cathode interface in optoelectronic devices. In particular, the pendant phosphonate groups impart water-alcohol solubility allowing easy solution processing, and improve electron injection thanks to both a favorable interfacial dipole of phosphonate groups and an intense coordination interaction between the phosphonate groups and Al cathode. In this work we synthesize alternating fluorene-benzothiadiazole copolymers by proposing a post-polymerization reaction to insert the phosphonate groups. Thanks to this approach it is possible to use standard Suzuki coupling conditions, simplifying the process of synthesis, purification and characterization. The polymer Poly[9,9-bis(6′-diethoxylphosphorylhexyl)-alt-benzothiadiazole] (P2), is tested in conventional organic solar cells as cathode interfacial layers showing, with respect to the control device, an increasing of all the photovoltaic parameters, with a final power conversion efficiency that reaches 5.35% starting from 4.6%. The same trend is observed for multilayered polymer light-emitting diodes with an external quantum efficiency of the P2-based PLED enhanced of 1.5 times with respect to the basic devices with bare Al cathode, and negligible roll-off efficiency. The synergic effects of energy gap modulation and of polar phosphonated pendant functionalities of P2 are compared with the corresponding fluorene-based polar homopolymer. Our results show that, not only a proper selection of side functionalities, but also the tailoring of the energy gap of cathode interfacial materials (CIMs) is a possible effective strategy to engineer cathode of different optoelectronic devices and enhance their performance.

The evolution of conjugated polyelectrolytes (CPEs) that transduce analyte–receptor interactions into detectable fluorescent responses in complex aqueous environments is predicated on advancements in molecular design and improved synthetic accessibility. Here, we demonstrate a simple post-polymerization modification protocol, based on thiol–ene click chemistry, that results in the rapid installation of sodium sulfate terminated side-chains to a poly(fluorene-co-ethynyl) scaffold. The fluorescence of the resulting water-soluble CPE is quenched by Fe3+, dequenched selectively by pyrophosphate (PPi), and accurately quantifies PPi within ±6 nM in artificial seawater. The broad utility of thiol–ene click chemistry should offer the straightforward integration of diverse sensing elements.

Electrostatic assembly of conjugated polyelectrolytes, which combine a π-conjugated polymer backbone with pendant ionic groups, offer an opportunity for tuning materials properties and a new route for formulating concentrated inks for printable electronics. Complex coacervation, a liquid-liquid phase separation upon complexation of oppositely charged polyelectrolytes in solution, is used to form dense suspensions of π-conjugated material. A model system of a cationic conjugated polyelectrolyte poly(3-[6'-{

Cationic π-conjugated polyelectrolytes (CPEs) were successfully intercalated into layered titanate (TiO2), while exfoliated layered titanates were reassembled into lamellar structures. The resulting composites showed significantly enhanced visible light absorbance and enhanced photocatalytic activity with respect to layered titanate, which was proven by the photodegradation of methylene blue in aqueous media under irradiation by visible light. Notably, some amount of tetrabutylammonium (TBA) used for the delamination of a layered titanate could be co-intercalated with CPEs, and the residual TBA could be removed via continuously repeating the intercalation process, maintaining the spatial arrangement and content of CPEs in the confined area of layered titanates. However, with the presence of TBA, the hybrid demonstrated greater performance in the photodegradation of methylene blue at any given period of time and almost complete degradation of such dye within 8 min. The significant difference in photocatalytic efficiency with or without TBA suggested that the TBA effectively reduced the surface energy at the interface between the organic components and aqueous medium, which was evidenced by the dispersity assessment of hybrids with or without TBA.

Several donor–acceptor type conjugated polyelectrolytes containing naphthalimide are developed. Different polymer chain configurations of the backbones of polymers lead to different photophysical properties. The para-substituted polymers show extended conformations with quite low quantum yields in high polarity solvents because of twisted intramolecular charge transfer features, while the meta-substituted polymers can form helices and demonstrated significantly improved quantum yields in water and methanol, as well as achieving sensitive, ultrafast and ratiometric detection of trace methylene blue in water. Ministry of Education (MOE) Nanyang Technological University The authors would like to thank the National Natural Science Foundation of China (No. 21572115) and Shenzhen Municipal Government (JCYJ20170817161303009) for financial support. Dr Y. Lu is thankful for the financial support from NTU, Singapore (MOE Tier 1 grant RG116/15).

In the last years, interfacial engineering has played a critical role in promoting the performance of optoelectronic devices as organic solar cells (OSC) and organic light-emitting diodes (OLEDs) since interfacial layers help to form an ohmic contact between the electrodes and the active layers, which is of great importance for charge collection/injection. Conjugated polyelectrolytes (CPEs), which are conjugated polymers bearing side-chain ionic functionalities such as anionic, cationic, or zwitterionic groups, have emerged as a new class of interfacial materials in thin film-based electronic devices thanks to their ability to reduce the barrier between electrode and active layer. In view of this, we designed and synthesized two novel low bandgap anionic copolymers with different anionic pendant groups and different conjugated backbones to obtain hole-transporting layer (HTL) materials as an alternative to commonly used poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). The functional behavior of these copolymers as anode modifiers is herein preliminarily investigated in an OLED prototype.

The current Covid-19 Pandemic caused by the highly contagious SARS-CoV-2 virus has proven extremely difficult to prevent or control. Currently there are few treatment options and very few long-lasting disinfectants available to prevent the spread. While masks and protective clothing and “social distancing” may offer some protection, their use has not always halted or slowed the spread. Several vaccines are currently undergoing testing; however there is still a critical need to provide new methods for inactivating the virus before it can spread and infect humans. In the present study we examined the inactivation of SARS-CoV-2 by synthetic conjugated polymers and oligomers developed in our laboratories as antimicrobials for bacteria, fungi and non-enveloped viruses. Our results show that we can obtain highly effective light induced inactivation with several of these oligomers and polymers including irradiation with near-UV and visible light. With both the oligomers and polymers, we can reach several logs of inactivation with relatively short irradiation times. Our results suggest several applications involving the incorporation of these materials in wipes, sprays, masks and clothing and other Personal Protection Equipment (PPE) that can be useful in preventing infections and the spreading of this deadly virus and future outbreaks from similar viruses.

The two-photon absorption properties of anionic poly(phenylene ethynylene)-type conjugated oligo- and polyelectrolytes are studied in molecularly dissolved and aggregated forms in aqueous solution. Several different polyvalent cations are used to induce aggregation. It is found that both materials in the aggregated form exhibit enhanced two-photon excited fluorescence (2PEF) and two-photon cross section (σ2) compared with the molecularly dissolved structures. The 2PEF and σ2 are unaffected by the nature of the polyvalent cation that is used to induce aggregation. The two-photon absorption cross section enhancement arises because of the increase in the difference dipole moment (Δμ) in the aggregates of the conjugated materials, an effect that is attributed to the introduction of charge transfer character into the aggregate excited state.

This work presents solution- and solid-state evidence of the enhancement of J-like aggregation of a cationic polythiophene (CPT) with isothiouronium functionalities (PT1), caused by a decrease in the polarity and hydrogen-bonding (H-bonding) capacity of the solvent, generated by using a 50:50 v/v 1,4-dioxane-water mixture (W-DI) instead of water. In solution, the presence of 1,4-dioxane (DI) seems to generate selective solvation, tuning the energy transfer within PT1 from inter-chain into intra-chain, enhancing J-like aggregation. On the other hand, during the casting process, the presence of DI directs the interaction with solid-substrates, generating an increase in the solid-state fluorescence, modifying the morphology from one similar to ballistic-aggregation (BA) into one similar to attachment limited aggregation (ALA), DI also modifies the SFE by increasing slightly its polar contribution (γSp) and decreasing the dispersive one (γSd). These results can be explained to be caused by a "coating" effect in presence of DI (as proposed before experimentally and computationally). Our results show a clear correlation between the solution- and solid-state properties of PT1 in each solvent, further validating the use of the fluorescence excitation spectra to trace J-like aggregation of water-soluble conjugated polymeric fluorophores in solution. This information could be useful for predicting and designing specific mesoscopic architectures of CPTs (and conjugated polyelectrolytes in general), which are molecules lacking of clear structure-function guidelines for designing high-performance polythiophene-based interlayer materials, especially for CPTs (and conjugated polyelectrolytes (CPEs) in general), particularly those with H-bonding capabilities. To the best of our knowledge the use of solution-state fluorescence excitation spectra to identify J-like aggregation of water-soluble conjugated polymers (CPs) has been scarcely used/discussed in literature and no correlation with solid-state properties was reported previously.

Conjugated polyelectrolytes (CPEs) have recently emerged as label-free materials for biosensing due to their intrinsic ability to transduce an amplified optical signal in response to interactions with different analytes. Herein, the conformational change of an anionic oligothiophene is exploited to generate a unique fluorescent response upon interaction with myristoylcholine (MyrCh). The variations observed in spectroscopic signals are explained in terms of a synergistic combination of hydrophobic and electrostatic forces involving the oligothiophene chains and MyrCh molecules, inducing the disassembling of oligothiophene chains. The enzyme acetylcholinesterase (AChE) is able to reverse this effect by catalyzing the hydrolysis of MyrCh; hence, its enzymatic activity can be monitored through the variation of fluorescence emission of the system. The oligothiophene sensing probe retains its conformational sensitivity with regard to the AChE-mediated cleavage of MyrCh upon immobilization onto a quartz substrate, which is accomplished by a "grafting onto" approach based on click chemistry. These results are encouraging for the further development of such a label-free system towards the fabrication of sensing devices that would incorporate CPEs and would be potentially useful for the specific detection of a wide range of bioanalytes. This journal is

We report the demonstration of antimicrobial conjugated polyelectrolytes (CPEs) with high NIR absorbance for selective and efficient photothermal killing of bacteria over mammalian cells. The antimicrobial CPE possessing quaternary ammonium (QA) terminated side chains (P1) shows higher binding preference and increased dark toxicity towards Gram-positive and Gram-negative bacteria over mammalian cells. Bestowed by π-conjugated backbones, P1 exhibits a high molar absorptivity of 39.8 L g−1 cm−1 at 808 nm with an efficient photothermal conversion efficiency of 33 ± 1%. Upon 808 nm laser irradiation, P1 shows enhanced bactericidal effects, but not to mammalian cells. Although the anionic CPE counterpart with the same polymer backbone but sulfonate terminated side chains (P2) possesses a similar photothermal conversion ability, it exhibits much lower antibacterial effects due to its low binding affinity. This study thus reveals that bacteria–CPE electrostatic interactions play a major role in bacterial recognition, although hydrophobic interactions also contribute.

A series of new conjugated polyelectrolytes (CPEs) with emissive tetraphenylethene-containing backbones and specific targeting pendants are synthesized and characterized. These new CPEs exhibit prominent aggregation-induced emission (AIE) properties, high photostability and low cytotoxicity, and can efficiently detect heparin and stain lysosomes in living cells.

The use of π-conjugated polymers (CPs) in conductive hydrogels remains challenging due to the water-insoluble nature of most CPs. Conjugated polyelectrolytes (CPEs) are promising alternatives because they have tunable electronic properties and high water-solubility, but they are often difficult to synthesize and thus have not been widely adopted. Herein, we report the synthesis of an anionic poly(cyclopentadienylene vinylene) (aPCPV) from an insulating precursor under mild conditions and in high yield. Functionalized aPCPV is a highly water-soluble CPE that exhibits low cytotoxicity, and we found that doping hydrogels with aPCPV imparts conductivity. We also anticipate that this precursor synthetic strategy, due to its ease and high efficiency, will be widely used to create families of not-yet-explored π-conjugated vinylene polymers.

Photocatalytic hydrogen evolution is viewed as a promising green strategy to utilize the inexhaustible solar energy and provide clean hydrogen fuels with zero-emission characteristic. The nature of semiconductor-based photocatalysts is the key point to achieve efficient photocatalytic hydrogen evolution. Conjugated materials have been recently emerging as a novel class of photocatalysts for hydrogen evolution and photocatalytic reactions due to their electronic properties can be well controlled via tailor-made chemical structures. Hydrophilic conjugated materials, a subgroup of conjugated materials, possess multiple advantages for photocatalytic applications, thus spurring remarkable progress on both material realm and photocatalytic applications. This minireview aims to provide a brief review of the recent developments of hydrophilic conjugated polymers/small molecules for photocatalytic applications, and special concern on the rational molecular design and their impact on photocatalytic performance will be reviewed. Perspectives on the hydrophilic conjugated materials and challenges to their applications in the photocatalytic field are also presented.

We report the synthesis of composite interlayers using alcohol-soluble polyfluorene (ASP)-wrapped single-walled carbon nanotubes (SWNTs) and their application as electron-transport layers for efficient organic solar cells. The ASP enables the individual dispersion of SWNTs in solution. The ASP-wrapped SWNT solutions are stable for 54 days without any aggregation or precipitation, indicating their very high dispersion stability. Using the ASP-wrapped SWNTs as a cathode interlayer on zinc oxide nanoparticles (ZnO NPs), a power conversion efficiency of 9.45% is obtained in PTB7-th:PC

The construction of intelligent self-assembly systems with cancer targeting photodynamic therapy abilities is highly required for increasing the precise therapeutic efficiency in clinical treatment. Herein, a cationic water soluble conjugated polymer (PFT-SH) functionalized with thiol groups was designed and synthesized via a palladium-catalyzed Suzuki coupling reaction. Firstly, PFT-SH can enter cells and form loose aggregations by hydrophobic and π–π stacking interactions. Secondly, a high level of H2O2 in cancer cells oxidizes sulfhydryl groups to disulfide bonds and then forms more and larger aggregations. Finally, PFT-SH showed remarkable ROS producing ability under white light irradiation with 78% quantum yields (ΦΔ). Due to this unique self-aggregation property, PFT-SH was successfully used to achieve in situ self-assembly specifically inside cancer cells for targeted imaging. Both the specific aggregation of PFT-SH in cancer cells and its ROS producing ability led to its use in the targeted killing of cancer cells through efficient photodynamic therapy.

Aqueous palladium-catalyzed direct arylation polymerization (DArP) of 2-bromothiophene derivatives 6-(2-(2-bromothiophen-3-yl)ethoxy)hexyl trimethylammonium bromide (T1) and 4-(2-(2-bromothien-3-yl)ethoxy)butylsulfonate (T2) is achieved. The supporting ligand, triphenylphosphine-3,3',3''-trisulfonic acid trisodium salt (m-TPPTs), facilitates DArP of both derivatives; however, its separation from the polymers by dialysis is difficult due to its strong aggregation in water and N,N-dimethylacetamide (DMAc). This is supported by dynamic light scattering, gel permeation chromatography (GPC), and single-crystal X-ray crystallography. Pyrimidine-Pd(OAc)2 is utilized in the DArP of T1 to afford PT1 without ligand contamination. Density functional theory calculations to determine the coordinating capability of the carboxylate/pivalic acid/water to palladium indicate the viability of implementing DArP in water. Finally, polyelectrolyte molecular-weight overestimation by GPC in water is attributed to the polyelectrolyte effect. Aggregation of the conjugated polyelectrolytes leads to a contracted hydrodynamic volume, and the molecular weight and dispersity assessed by GPC in DMAc significantly deviate from the actual values. An objective approach to evaluate the molecular weight for conjugated polyelectrolytes requires further development.

Conducting polymer hydrogels (CPHs) are an attractive class of materials that synergize the electrical properties of organic semiconductors with the physical properties of hydrogels. Of particular interest is the implementation of CPHs as electrode materials for electrochemical energy storage by taking advantage of redox-tunable conjugated backbones and the large electroactive surface area. Herein, the use of 2D electrolytes as an effective post-polymerization additive to enhance the pseudocapacitive performance of CPHs, is demonstrated. By using the self-doped conjugated polyelectrolyte CPE-K hydrogel as a model system, improvements in cycling stability, specific capacitance and working voltage window upon addition of the 2D electrolytes, are shown. Furthermore, positively charged 2D electrolytes to be more effective than their negatively charged counterparts are revealed. Rheology measurements and SEM imaging indicate that the 2D electrolytes serve as non-covalent cross-linkers that help in forming a mechanically more robust and highly percolated conducting network. These results provide a new and simple to execute post-polymerization strategy to optimize the electrochemical performance of CPH-based pseudocapacitors. National Research Foundation (NRF) This work was supported by the National University of Singapore start up grant R143-000-A97-133 and the Medium-Sized Centre (MSC) grant from the National Research Foundation (NRF) of Singapore, Prime Minister's Office. G.Q. acknowledges funding from the President's Graduate Fellowship (PGF) under the National University of Singapore.