Search

Oppositely charged, water-soluble polyelectrolytes undergo a spontaneous complexation and phase separation process with applications in fields spanning food science, origin of life studies, biomedicine, underwater adhesives, and general materials science. Specifically, associative phase separation leading to complex coacervation of oppositely charged polyelectrolytes has been extensively studied to understand prebiotic organization and to inform research into synthetic cell mimics. However, the phase behavior of conjugated polyelectrolytes (CPEs), macromolecules analogous to chromophores and light-harvesting antennae found in photosynthetic organelles, has been investigated only minimally. Many questions remain regarding controlling of CPEs phase behavior, and how the formation of dense CPE-rich phases influences the resultant photophysics of theses molecular semiconductors. The work in this thesis primarily focuses on gaining a systematic understanding of the influence of ionic strength on the phase behavior of CPEs. The main tools used in this inquiry are steady-state absorption (or optical density (OD)) and photoluminescence (PL), time-resolved photoluminescence (TRPL), time resolved photoluminescence anisotropy, fluorescence microscopy, and fluorescence lifetime imaging (FLIM). The major findings of this work are as follows: the concentration and identity of cations in solution were found to manipulate the radiative decay rate and the exciton diffusion dynamics highlighting the importance of the interactions of the CPE complex with ions differing in polarizability and size; the influence of molecular ions leads to a transition from a two-phase system to an optically clear single phase with increased lifetime and decrease depolarization rate not accessible with similar concentrations of atomic salts; the chemical structure of a CPE can be rationally designed to undergo liquid/liquid phase separation to stabilize a semiconducting coacervate microstate; the interaction between ethyleneglycol units and K+ ions is critical in forming the coacervate phase; excited state energy transfer between the donor and acceptor CPEs occurs within the highly electronically coupled complex coacervate droplet phase.

This dissertation is concerned with the fabrication and characterization of organic electrochemical transistors (OECTs) made from polyelectrolytes based on the material PCPDTBT-SO3-Na (CPE-Na). OECTs are electrolyte-gated transistors that allow the electrolyte to permeate into the bulk of the film and directly changes the doping state of the bulk of the semiconducting layer. The relationship between the molecular structure of the polyelectrolytes and the material properties are explored in the lens of optimizing device characteristics in OECTs. The first chapter of this thesis focuses on the development of OECTs made using PCPDTBT-SO3-K (CPE-K) as the active layer. While the large majority of OECT research still utilizes poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as the active layer, a few new OECT materials have been recently reported. CPE-K has been used in the past for applications such as DNA-detection, thermoelectric devices and as interlayers in organic photovoltaic devices. Conjugated polyelectrolytes (CPEs) represent a promising and unique class of materials which are characterized by their conjugated carbon backbone and pendant ionic chains. Their water solubility in addition to their electronic and ionic conductivity makes them an ideal candidate for OECT applications. Using various spectroscopic and electric characterization techniques, CPE-K was fully characterized so that it could be accurately compared to other OECT materials reported in the literature. In fact, CPE-K is among the short list of high-performance OECT materials. The techniques used in this work was used to shed light on the operational mechanism of CPE-based OECTs. In addition, the effective use of interdigitated contacts was used to increase the transconductance of OECT devices.The second portion of this thesis expands on the work of CPE OECTs, by exploring their structure-property-relationship. A series of CPE-Na polymers with varying sidechain lengths were synthesized by collaborator Luana Llanes from the lab of Professor Guillermo Bazan. A series of CPE-Na with increasing alkyl chain distances (2-5 methylene units) were synthesized. The purpose of synthesizing these materials was to explore the effect of varying the distance of the pendant charged sulfonate on the side-chain. CPE-Na is a self-doped polymer, due to the negative charge on the sulfonate stabilizing the positively charged polaron. It was hypothesized that reducing the side-chain length would result in easier doping of the CPE due to the proximity of the sulfonate. To our surprise, the opposite trend was observed. By using a wide range of characterization techniques, the structure-property-relationship between the sidechain length and ease of doping of the CPE backbone was explored. The next chapter of the thesis switches topics to organic field-effect transistors (OFETs). Due to convenience and low leakage current, many OFETs use silicon dioxide as the gate dielectric material. As demonstrated by Dr. Hung Phan, trap sites at the dielectric-semiconductor interface result charge trapping. This charge trapping results in unwanted artifacts such as hysteresis, double-slope nonideality characteristics, and reduction in current when the device is continuously biased. The fluoropolymer P(VDF-HFP) was used as a dielectric material. We found that the device transfer characteristics are heavily dependent on the processing conditions and choosing the proper grade of P(VDF-HFP). We presented the correct choice of processing conditions and material grade results in ideal transfer characteristics such as high on-off ratio, low threshold voltage, low hysteresis and high current stability.The final section of the thesis discusses a project to explore the structure-property relationship of a group of 12 different n-type non-fullerene acceptor small molecules. Non-fullerene acceptors (NFAs) have recently become an area of interest to researchers aiming to develop high performance organic solar cells due to their promising electronic properties and greater tunability relative to fullerene-based acceptors. Despite the success of NFAs in organic solar cells, there have only been a few studies looking at the electron mobility of these materials. A collection of 12 NFAs with a variety of core groups and sidechain configurations were tested as the active layer in an organic field-effect transistor (OFET) to measure the mobility of horizontal charge transport.

Bioelectronics concerns the integration of electronic elements with biological systems to form functional devices including biosensors for detection and analysis, neuroelectronic junctions, and biofuel cells for energy conversion and catalysis. A fundamental part of any bioelectronic system is the electronic coupling and transport at the various biotic/abiotic interfaces between biomaterials and electronic supports. The development and study of materials that modulate charge transport across these interfaces is therefore an area of interest. Advances in increasing the synergy between electronics and biology will see impacts in not only our understanding of system, cell, and molecular biology, but also more efficient electronics for conversion of bioenergy. In this development, we have focused on the implementation of redox-active conjugated electrolytes at the biotic/abiotic interface for amplifying biocurrent collection.In specifically-designed microbial bioelectrochemical systems, bacteria interface with electrodes to catalyze the interconversion of chemical and electrical energy. Membrane modifiers called conjugated oligoelectrolytes (COEs), defined by their conjugated core and peripheral ionic pendant groups, have been shown to increase the ability of electrogenic microbes to electronically communicate with abiotic components through a number of indirect factors including increasing electrode colonization and coulombic efficiency. However, precise control over the mechanism of current enhancement remained to be seen. Two ferrocene-containing COEs called DVFBO and F4-DVFBO were designed to test voltammetric control over biocatalytic current production. Both COEs have a π-delocalized core capped on each end by ferrocene units and show similar optical properties, affinity for the membrane, and toxicity, but fluorination of the core (F4-DVFBO) results in a higher redox potential (422 ± 5 mV compared to 365 ± 4 mV vs Ag/AgCl for DVFBO). The COEs were tested in anaerobic microbial three-electrode electrochemical cells (M3Cs) containing the model electrogenic bacterium Shewanella oneidensis MR-1. At a low electrode potential, the addition of the COEs produced negligible current enhancement compared to controls. However, at E = 365 mV, DVFBO increased steady-state biocurrent 67 ± 12% relative to controls while F4-DVFBO only increased biocurrent by 30 ± 5%. With no change in electrode colonization, cyclic voltammetry supports that DVFBO is the primary conduit of the increased catalytic current and shows F4-DVFBO has less activity at this poised potential. Overall, this work demonstrates the ability to modulate electron transfer from microbial species exclusively via the oxidation potential of the COE.While microbial membrane modification with redox-active COEs led to improvement in current extraction, a two-dimensional electrode structure limits the surface area for electroactive bacteria attachment and restricts efficient substrate and buffer diffusion. Conjugated polyelectrolytes represent a complementary interfacial materials strategy to enhance biotic/abiotic electronic coupling. First, the mixed ionic-electronic conduction properties of the self-doped conjugated polyelectrolyte CPE-K were investigated with respect to hydration. Films of CPE-K showed both increasing ionic and electronic conduction with hydration. Results indicate that the increase in electronic conduction was due to both increased number of free charge carriers and closer π-π stacking.Following this characterization, CPE-K was used as a conductive matrix to electronically connect a three-dimensional network of Shewanella oneidensis MR-1 to a gold electrode. At critical CPE-K concentrations, these biocomposites spontaneously assemble from solution into an intricate arrangement of cells within a conductive polymer matrix, thereby increasing biocurrent ~150-fold over control biofilms in M3C tests. While increased biocurrent is due to more cells in communication with the electrode, current extracted per cell is also enhanced indicating efficient long-range electron transport. Further, biocomposites show almost an order-of-magnitude lower charge transfer resistance than CPE-K alone, supporting that the electroactive bacteria and the conjugated polyelectrolyte work synergistically towards an effective electronic biocomposite. Examination of these biocomposites in microbial fuel cell configurations reinforces the need for continued pursuit of synthetic designs to improve the biotic/abiotic interface in bioelectronics.

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...

Organic photovoltaics (OPVs) based on conjugated polymer and small molecule semiconductors are a promising technology for solar energy capture. The compatibility of organic semiconductors with solution processing allows OPV devices to be prepared using high-throughput manufacturing processes on flexible substrates, opening up applications not available to most commercial technologies. The most efficient devices utilize a bulk heterojunction (BHJ) active layer, a two-component solid state mixture that provides efficient photocurrent generation, but also presents several performance-limiting issues. The consequences of structural and energetic disorder in these systems can be difficult to quantify using existing experimental techniques. This dissertation describes three studies presenting new approaches to measuring the morphological, energetic, and interfacial properties of BHJ solar cells. First, a study of static disorder in the density of states (DOS) is carried out in-situ in several BHJ blends. DOS tail states are characterized here by combining the charge carrier density dependence of Voc with disorder-dependent band bending behavior. A direct connection is found between disorder observed within donor and acceptor phases and the overall impact of disorder on open-circuit voltage. Disorder is shown to be both material- and morphology-dependent, significantly impacting device performance. Next, a new technique, polarization-dependent photoconductive atomic force microscopy, is used to measure local orientation-dependent photocurrent in BHJ active layers with resolution below 100 nanometers. A high-performing small molecule donor is found to exhibit in-plane, micron-scale orientational order not seen by typical diffraction or topography measurements. The observed liquid-crystalline networks provide a unique picture of morphology that goes beyond the typical binary of crystalline vs amorphous. Lastly, a technique is presented to measure the ion transport properties in conjugated polyelectrolytes (CPEs) used as interlayers in OPVs. Ion motion is characterized using Kelvin probe force microscopy to observe the relaxation over time of bias-stressed CPE device channels. Based on studies of systematically varied CPE structures, the number of ionic side chains per monomer shows a strong correlation with ionic conductivity. These results help inform the material design of CPEs, not just for interlayers in organic optoelectronic devices, but also for a number of emerging mixed ionic-electronic conductor applications.

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 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.

Two benzimidazole-based conjugated polyelectrolytes (+)-PPBIPV and (-)-PPBIPV which have opposite charges on their side chains were synthesized via Heck coupling reaction and characterized by 1H-NMR, UV-vis and PL spectroscopy. These two polyelectrolytes are both consisted of benzimidazole derivatives and phenylenevinylene units. The absorption and emission spectra reveal that the polymers both have solvent-dependency and concentration-dependency, and they exhibit aggregation effect in aqueous solution. In the respect of ion detection, the aqueous solution of (+)-PPBIPV has excellent selectivity and sensitivity for Fe3+. Moreover, Pd2+ can almost completely quench the fluorescence of (+)-PPBIPV in methanol solution, and its quenching constant K SV is 5.93×104 M-1. For (-)-PPBIPV, Sn2+ can double the fluorescence intensity of its aqueous solution, while (-)-PPBIPV has good identification for Fe3+ in methanol with a K SV = 3.44×105 M-1. Hence, two polyelectrolytes have considerable potential to become effective fluorescent sensing materials for some specific metal ions. All of the stoichiometric relationships between metal ions and conjugated polyelectrolytes were calculated using Benesi-Hildebrand equation.

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.

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.

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.

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.

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.

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.

Phosphonium-based polythiophene conjugated polyelectrolytes (CPEs) with three different counterions (dodecylsulfate, octylsulfate and perfluorooctane sulfonate) are synthesized to determine how the nature of the counterion affects the thermal properties, the self-assembly in thin films and the performance as the cathode interfacial layer in polymer solar cells (PSCs). The counterion has a significant effect on the thermal properties of the CPEs, affecting both their glass transition and crystalline behaviour. Grazing-incidence wide-angle X-ray scattering studies also indicate that changing the nature of the counterion influences the microstructural organization in thin films (face-onversusedge-on orientation). The affinity of the CPEs with the underlying photoactive layer in PSCs is highly correlated with the counterion species. Finally, in addition to an increase of the power conversion efficiency ofca15% when using these CPEs as cathode interfacial layers in PSCs, a higher device stability is noted, compared to a reference device with a calcium interlayer. (c) 2020 Society of Industrial Chemistry This work was supported by the CNRS and the Universite de Montpellier. This work was also supported in part by the Science Foundation Ireland under grant no. 12/IP/1608. Research in Mons is supported by FNRS-FRFC (2Dto3D project - EOS programme) and Region Wallonne (OPTI2MAT excellence programme). The University of Mons and Hasselt University co-authors are grateful for financial support by the Science Policy Office of the Belgian Federal Government (BELSPO; PAI/IAP 7/05). JK is a postdoctoral fellow of the Research Foundation - Flanders (FWO Vlaanderen). NVdB thanks the Vrije Universiteit Brussel for a post-doctoral grant. The HINT COST action MP1202 and French-Irish programme 'Hubert Curien Ulysses' (31998ZF) are also acknowledged for support. This research has also been supported by the European Commission under the 7th Framework Programme through the 'Research Infrastructures' action of the 'Capacities' programme (contract no. CP-CSA_INFRA-2008-1.1.1 Number 226507-NM13). We further thank the Diamond Light Source for beamtime at the I07 beamline (experiment SI13868) and TA Instruments for the RHC equipment. Clement, S (corresponding author), Univ Montpellier, ENSCM, CNRS, ICGM, Montpellier, France. sebastien.clement1@umontpellier.fr

Conjugated polymers with ionic pendant groups (CPEs) are receiving increasing attention as solution-processed interfacial materials for organic solar cells (OSCs). Various anionic CPEs have been successfully used, on top of ITO (Indium Tin Oxide) electrodes, as solution-processed anode interlayers (AILs) for conventional devices with direct geometry. However, the development of CPE AILs for OSC devices with inverted geometry is an important topic that still needs to be addressed. Here, we have designed three anionic CPEs bearing alkyl-potassium-sulfonate side chains. Their functional behavior as anode interlayers has been investigated in P3HT:PC61BM (poly(3-hexylthiophene): [6,6]-phenyl C61 butyric acid methyl ester) devices with an inverted geometry, using a hole collecting silver electrode evaporated on top. Our results reveal that to obtain effective anode modification, the CPEs’ conjugated backbone has to be tailored to grant self-doping and to have a good energy-level match with the photoactive layer. Furthermore, the sulfonate moieties not only ensure the solubility in polar orthogonal solvents, induce self-doping via a right choice of the conjugated backbone, but also play a role in the gaining of hole selectivity of the top silver electrode.

Polymer solar cells (PSCs) based on non-fullerene acceptors have the advantages of synthetic versatility, strong absorption ability, and high thermal stability. These characteristics result in impressive power conversion efficiency values, but to further push both the performance and the stability of PSCs, the insertion of appropriate interlayers in the device structure remains mandatory. Herein, a naphthalene diimide-based cathode interlayer (NDI-OH) is synthesized with a facile three-step reaction and used as a cathode interlayer for fullerene and non-fullerene PSCs. This cationic polyelectrolyte exhibited good solubility in alcohol solvents, transparency in the visible range, self-doping behavior, and good film forming ability. All these characteristics allowed the increase in the devices’ power conversion efficiencies (PCE) both for fullerene and non-fullerene-based PSCs. The successful results make NDI-OH a promising cathode interlayer to apply in PSCs.

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.

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.

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.

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

International audience; Poly(3,4-ethylenedioxythiophene)–polystyrene sulfonate (PEDOT:PSS) conjugated polymer blend and a cationic poly(3-hexylthiophene) (P3HT)-based conjugated polyelectrolyte incorporating imidazolium ionic side groups were first adsorbed as monolayer on inorganic colloidal particles. At the plateau of adsorption isotherm, adsorbed amount of PEDOT:PSS on alumina particles appears lower than the adsorbed amount of P3HT on silica particles. Both polyelectrolytes strongly modify the surface charge of particles as reveals by zeta potential variation. Functionalized particles were then assembled using Layer-by-Layer method in order to prepare (PDDA/Al2O3-PEDOT:PSS)n and (SiO2-P3HT/PEDOT:PSS)n conductive multilayer film. Thicker PDDA/Al2O3-PEDOT:PSS films were elaborated when a drying step was added during the LbL build-up. The same effect was observed when composite particle concentration was increased from 1 to 10 g.L−1. Electrical behavior of film was completely modified in comparison with PDDA/PEDOT:PSS assembly. After heating at 150 °C, no conductivity was detected due to microcracks visible on SEM images. For SiO2-P3HT/PEDOT:PSS assembly, thickness is higher than for PDDA/Al2O3-PEDOT:PSS assembly using the same experimental procedure. However, even if two conductive polyelectrolytes were embedded into the film, conductivity was too low at 30 °C to be measured by van der Pauw technique probably due to the cracking of the film induced by incorporation of silica particles.

Conjugated polyelectrolytes based on n-type backbone (n-CPEs) were recently developed as highly efficient cathode interlayers for polymer solar cells (PSCs), but the relevance between structure and property of n-CPEs has not been fully understood yet. Herein, three new self-doping n-CPEs based on the diketopyrrolopyrrole (DPP) alternated fluorene framework were reported. The effect of the number and location of polar groups on the properties of the new n-CPEs has been systematically studied. It can be found that the photoelectric properties of n-CPEs were sensitive to the number and location of polar groups. A tunable work function (WF), interfacial interaction, and conductivity of these n-CPEs can be readily realized by regulating the number and location of polar groups on the electron skeleton. The polar groups directly appending on the electron-withdrawing DPP unit can promote a stronger n-type self-doping and lower WF than the ones attached on the electron-pushing fluorene unit. Increasing the number ...

Self-compensated (SC) hole-doped conjugated polyelectrolytes with high work functions can provide efficient hole-injection and -collection layers for organic and other semiconductor devices. If these films can be photocrosslinked, the semiconductor overlayer can be deposited from a wider range of solvents, enabling flexibility in device design and fabrication. However, a generic photocrosslinking methodology for these materials is not yet available. Here, we demonstrate that sFPA82-TfO, the recently developed bis(fluorophenyl azide) photocrosslinker that is also i-line compatible, can surprisingly give 100% efficient photocrosslinking for SC hole-doped conjugated polyelectrolytes, i.e., one crosslink per reactive moiety, using mTFF-C2F5SIS-Na, a triarylamine–fluorene copolymer, as the model polyelectrolyte, without degrading its ultrahigh work function of 5.75 eV. The photocrosslinking efficiency is much higher than in the corresponding undoped polyelectrolyte and nonconjugated polyelectrolyte films, wher...

There is substantial urgency to create artificial light-harvesting systems that are relatively inexpensive and capable of absorbing a significant fraction of the solar spectrum. Molecular materials possess a number of attractive characteristics for this purpose, such as their light weight, spectral tunability, and the potential to use self-assembly to form large structures capable of executing multiple photophysical processes required for photoelectric energy conversion. In this work, we demonstrate that ionically assembled complexes composed of oppositely charged conjugated polyelectrolytes (CPEs) that function as excitonic donor/acceptor pairs possess 10 significant potential as artificial energy transfer antennae. We find that, upon complexation in water, excitation energy is transferred from the donor to the acceptor CPE in less than 250 fs—a timescale that is competitive with natural light-harvesting antennae. We further find that the state of CPE chain extension and thus spatial delocalization of th...

Photon pressure has been used to induce the aggregation from solution of a series of photoluminescent conjugated polyelectrolytes containing tetraphenylethene units. These polymers show steady-state and time-resolved emission properties that are dependent on the local chromophore environment that can be influenced by the degree of intra- and inter-molecular interactions, which enables the photoaggregation process to be monitored by time-resolved fluorescence imaging techniques. Structural differences in the polymer lead to variations in the photo-induced aggregation behaviour.

Conjugated polyelectrolytes and their precursors as electron-injection layer (EIL) in polymer light-emitting diode have attracted extensive attention because they allow the use of environmentally stable high work function metals as cathode with efficient electron injection. Here, for the first time, we find that an undesirable green emission component (470–650 nm) in the electroluminescence spectra is observed during continuous operation of deep-blue emission β-phase poly(9,9-dioctyl-2,7-fluorene) (β-PFO) device upon introducing polyelectrolyte poly[9,9-bis(6′-(18-crown-6)methoxy)hexyl fluorene] chelating to potassium ion (PFCn6:K+) as EIL. This phenomenon also happens to nonchelating PFCn6, poly[(9,9-bis(3′-(N,N-dimethylamino)propyl)-2,7-fluorene)-alt-2,7-(9,9-dioctylfluorene)], or even nonemissive poly[4-((18-crown-6)methoxy)methyl styrene] chelating to K+ (PSCn6:K+). It can be ascribed to electric-field induction accompanied by thermal motion of a highly polar side chain in the polyelectrolyte leading ...

Organic light-emitting transistors (OLETs) show the fascinating combination of electrical switching characteristics and light generation capability. However, to ensure an effective device operation, an efficient injection of charges into the emissive layer is required. The introduction of solution-processed conjugated polyelectrolyte (CPE) films at the emissive layer/electrode interface represents a promising strategy to improve the electron injection process by dipole formation. However, their use in optoelectronic devices also involves some limitations because of the ionic nature of CPEs. In this context, neutral conjugated polar polymers (CPPs) represent a valid alternative to CPEs because the conjugated backbones of CPPs are functionalized with polar nonionic side groups, thus avoiding ion-dependent drawbacks. By introducing a layer of polyfluorene-containing phosphonate groups underneath the metal electrodes, we here demonstrate a substantial improvement of the electron injection properties into the OLET-emissive layer and, accordingly, a more than 2-fold increased light power and a 5 times higher external quantum efficiency of p-type OLETs in comparison with reference devices without any interlayer. The great benefit of using a transparent glass substrate allowed to selectively investigate the morphological and photoluminescent characteristics of both CPE- and CPP-buried interlayers within complete OLETs by means of an optical scanning probe technique. This, together with a thorough optoelectronic characterization of the figures of merit of working light-emitting devices, allowed to disclose the origin of the improved optical performance of CPP-based devices as well as the operation mechanisms of the investigated interlayer in the corresponding OLETs.

Three conjugated polyelectrolytes(CPEs) based on thiophene, thieno[3,2-b]thiophene, and 2,2'-bithiophene were designed and synthesized. The CPEs were successfully incorporated into polymer solar cells as pH-neutral hole-transporting layer(HTL) via solution process. The interfacial dipole and work function(WF) of CPE-coated ITO were controlled by the dipole moment of the polymer, which was in turn determined by the stereochemical properties of the molecular structure. CPE-coated ITOs showed sequentially stronger dipole moments due to an increase in the electrostatic repulsion in the molecules. The PCE of device with PFT as the HTL was maintained accompanied by 16% decrease when PEDOT:PSS-based device decreased over 50%.

A series of cationic phosphonium-based conjugated polyelectrolytes (CPCPs, named as PFP-F, PFP-Cl, PFP-Br, PFP-I) with different counteranion were developed as individual cathode interface material and ZnO dopant for polymer solar cells (PSCs). The CPCPs are soluble in environmentally friendly polar solvents, which is beneficial to fabricating multilayer organic optoelectronic devices. Besides, the CPCPs show better thermal stability than traditional quaternary ammonium salt-based conjugated polyelectrolytes. The CPCPs perform efficiently as electrode modifiers to lower the work function of metal electrode and possess capability to n-dope PC71BM, both of which contribute to the improved performance of polymer solar cells. Significant enhancement in power conversion efficiency from 6.3% to >9.0% were achieved by employing a thin layer of CPCP between active layer and Al electrode in polymer solar cells with conventional device structure. Moreover, the CPCPs can be used as dopants to ZnO. The formed ZnO:CPCP hybrids can improve the interface contact between bottom contacts and active layer in inverted solar cells, resulting in improved performance.

Two novel poly(pyridinylene vinylene) (PPV)-type conjugated polyelectrolytes 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) were synthesized via Heck coupling reaction and characterized by 1H nuclear magnetic resonance (NMR), ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy. The two polymers consisting of meta-position substituted pyridinylenes as the metal recognition unit and a water-soluble divinyl-benzene derivative in the backbones. 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) both exhibit strongest fluorescence in methanol and weakest fluorescence in water among common polar solvents. In respect of ion detection, 3,5-PPYPV-(2+) has an excellent identifiability for Pd2+ in methanol with the K_SV value of 1.1×105 m −1 while 2,6-PPYPV-(2+) has a good selectivity for Cu2+ and Hg2+ in aqueous solution. And all the Stern-Volmer plots of 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) in fluorescence quenching for metal ions have favorable tendencies. All the results suggest that 2,6-PPYPV-(2+) and 3,5-PPYPV-(2+) are promising materials in the applications of high performance chemosensors for some specific metal ions.

Dopant-free silicon (Si)/organic heterojunction solar cells (HSCs) have drawn much attention due to their immense potential in achieving high power conversion efficiencies (PCEs) with simple device architectures and fabrication procedures. However, unsatisfied rear-contacts severely hinder further improvement in PCEs for these promising HSCs. Exploring effective cathodic interfacial materials with low temperature fabrication to replace conventional diffusion layer shows the extremely importance of technical innovation. Here, poly[4,8-bis(2-ethylhexyloxyl)benzo[1,2-b:4,5-b’]dithiophene-2,6-diyl-alt-ethylhexyl-3-fluorothieno[3,4-b]thiophene-2-carboxylate-4,6-diyl] (PTB7)-based narrow band-gap conjugated polyelectrolytes, PTB7-NBr and PTB7-NSO3, are firstly employed as effective cathodic interfacial materials in Si/organic HSCs to improve the passivation and electron transporting property at n-Si/Al interface. The low-temperature proceeded electron-selective contact of n-Si/PTB7-NBr/Al gives a contact resistivity as low as 6.7 ± 0.8 mΩ cm2, upon it a remarkable PCE of 16.0% is finally obtained from a completely dopant-free Si/organic HSC. The understanding of conjugated polyelectrolytes on interfacial modification may lead a path to fabricate high performance Si/organic heterojunction devices with efficient charge transfer process at a simplified fabrication process.

Conjugated polyelectrolytes (CPEs) have been applied as sensors for various small molecules and ions including biologically important ions. Here we report the synthesis of two different polyphenylene ethynylene (PPE) type cationic CPEs and studied their biologically important phosphate ion sensing properties. These CPEs are substituted with branched polyammonium units; polymer P-O-3 features an –O–CH2– linker between phenylene units and the cationic side chains, whereas P-C-3 has an –CH2– linker. The different linkers lead to a difference in intrinsic tendency of the CPEs to aggregate in water. We report amplified fluorescence quenching, Stern–Volmer constants (Ksv), fluorescence correlation spectroscopy, and different anion sensor response of the polymers. The investigation of these two CPEs for anion sensing reveals that they are considerably more sensitive to di-phosphonates than to di-carboxylates or di-sulfonates. Fluorescence quenching is a result of polymer aggregate formation due to electrostatic interactions and hydrogen-bonding between dianions and the cationic CPEs. Polymer P-C-3, which has lower tendency to aggregate in water, was found to be a more efficient sensor than P-O-3 for PPi and ATP. Stern–Volmer quenching constants (Ksv) of P-C-3 by PPi and ATP are greater than 105 M−1. Furthermore, a real-time fluorescence assay for ALP-catalyzed hydrolysis of pyrophosphate (PPi) is demonstrated.