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An organic soluble precursor polymer was prepared by direct (hetero)arylation polymerization of 3,4-ethylenedioxythiophene (EDOT) with a solubilizing, 3,4-propylenedioxythiophene (ProDOT) derivative bearing ester-functionalized side chains. Chemical defunctionalization of the polymer, using base to hydrolyze the esters, yields a conjugated polyelectrolyte (CPE) that is readily soluble in water. This aqueous soluble CPE can then be processed using high-throughput coating methods from water-based inks. Postprocessing functionalization of the polymer film using dilute acid creates a solvent resistant film that is compatible with both organic and aqueous electrolyte systems for redox switching. The introduction of an unfunctionalized EDOT unit results in a soluble polymer that has a low oxidation potential and that is highly electroactive and pseudocapacitive in a wide voltage range (2 V in propylene carbonate-based electrolytes and 1.55 V in aqueous electrolytes) making it an attractive material for lightweight and flexible supercapacitors. Films of this copolymer demonstrate exceptionally rapid redox switching (10 V/s) and higher mass capacitance in aqueous electrolyte solutions than in organic solutions. Supercapacitors incorporating the solvent resistant copolymer exhibit symmetric charge/discharge behavior at currents of up to 20 A/g (1 s discharge) and are able to maintain >75% of the initial capacitance over 175 000 cycles using 0.5 M NaCl/water as the device electrolyte. Rapid electrochromic switching (~0.2 s) from vibrant blue to colorless is also maintained in this salt-water electrolyte. The versatility of this polymer is further shown in a series of organic and aqueous electrolyte systems, including biologically compatible electrolytes (NaCl/water, Ringer's solution, and human serum) and even sport drinks (Gatorade and Powerade), demonstrating the robustness of this polymer to differing ionic conditions. Based on these results, it is apparent that this polymer and similar systems have great potential in multiple electrochemical applications such as electrochromic devices, supercapacitors, and biocompatible devices. [ABSTRACT FROM AUTHOR]

Since the interfacial order of conjugated polymers plays an essential role for the performance of field-effect transistors, comprehensive understanding on the charge carrier transport in ultrathin semiconducting films below thicknesses of 10 nm is required for the development of transparent and flexible organic electronics. In this study, ultrathin films based on poly(3-hexylthiophene) as conjugated polymer model system with a thickness range from single monolayer up to several multilayers are investigated in terms of microstructure evolution and electrical properties of different molecular weights. Interestingly, a characteristic leap in field-effect mobility is observed for films with thickness greater than four layers. This threshold mobility regarding film thickness is attributed to the transition from 2D to 3D charge carrier transport along with an increased size of the P3HT aggregates in the upper layers of the film. These results disclose key aspects on the role of the film interlayer on the charge carrier transport through conjugated polymers in transistors. [ABSTRACT FROM AUTHOR]

Poly(thienylene vinylene)s (PTVs) are a unique class of low bandgap conjugated polymers that have received relatively little attention in organic electronic applications due to the limitations in conventional synthetic methodologies that are not capable to produce PTV structures beyond the rudimentary forms. We report here facile synthetic methods, combining acyclic diene metathesis (ADMET) and postpolymerization modification reactions, toward a series of structurally diverse PTVs. Specifically, halogen substituents including F, Cl, Br, and I, and conjugated thienyl groups bearing different substituents, have been installed onto every thiophene unit along the PTV backbones. While halogen substitution lowers both the HOMO and LUMO energy levels of the polymers, the overall optical properties are similar to the conventional unsubstituted PTVs. On the other hand, with increasing sizes of halogen atoms, the polymer crystallinity decreases caused by steric hindrance induced main-chain nonplanarity as suggested by density functional theory (DFT) calculations and confirmed by X-ray diffraction (XRD) and absorption measurements. With the cross-conjugated thienyl side-chains, the PTV polymers are all amorphous due to the large dihedral angles between the main-chain and side-chain thienyl rings. However, with strongly electron-withdrawing groups attached on the side-chain thiophene rings, new electronic transitions located at lower energies are observed, which have never been observed in PTVs and are assigned to main-chain to side-chain intramolecular charge transfer (ICTs) transitions. Such ICT transitions can potentially alter the PTV excited states ordering and dynamics, as evidenced by the appearance of fluorescence in one of the cross-conjugated PTVs bearing strong electron-withdrawing cyanoester vinylene groups. Applications of these new PTVs in bulk heterojunction (BHJ) organic solar cells (OSCs) have been attempted, and preliminary results showed much improved performances over devices using conventional PTVs, especially for those applying the cross-conjugated PTVs. Our methodologies are highly versatile in preparing PTVs with systematically varied structures that for the first time provide means to study and gain better understandings on the structure-property relationships of this unique class of materials and to potentially generate novel polymers tailor-designed for specific electronic applications. [ABSTRACT FROM AUTHOR]

The article discusses the scientific origins and approaches in designing low-bandgap polymers/molecules for use in organic electronics. Topics include the invention of polyphenylenevinylenes in 1990s which led to the development of conjugated polymers for organic electronics, the intrinsic properties of organic semiconductors and their advantages and the new material design concepts that will drive ultrahigh performance for organic electronics.

A novel, highly soluble chromophorefor use in organic electronicsbased on an indigoid structure is reported. Copolymerization withthiophene affords an extremely narrow band gap polymer with a maximumabsorption at ∼800 nm. The novel polymer exhibits high crystallinityand high ambipolar transport in OFET devices of 0.23 cm2V–1s–1for holes and 0.48 cm2V–1s–1for electrons.OPV device efficiencies up to 2.35% with light absorbance up to 950nm demonstrate the potential for this novel chromophore in near-IRphotovoltaics. [ABSTRACT FROM AUTHOR]

Continuoustuning of the backbone conformation and interchain distanceof a π-conjugated polymer is an essential prerequisite to unveilthe inherent electrical and optical features of organic electronics.To this end, applying pressure in a hydrostatic medium or diamondanvil cell is a facile approach without the need for side-chain syntheticengineering. We report the development of high-pressure, time-resolvedmicrowave conductivity (HP-TRMC) and evaluation of transient photoconductivityin the regioregular poly(3-hexylthiophene) (P3HT) film and its bulkheterojunction blend with methanofullerene (PCBM). X-ray diffractionexperiments under high pressure were performed to detail the pressuredependence of π-stacking and interlamellar distances in P3HTcrystallites and PCBM aggregates. The HP-TRMC results were furthercorrelated with high-pressure Raman spectroscopy and density functionaltheory calculation. The increased HP-TRMC conductivity of P3HT underpressure was found to be relevant to the planarity of the backboneconformation and intramolecular hole mobility. The effects of pressureon the backbone planarity are estimated to be ∼0.3 kJ mol–1based on the compressibility derived from the X-raydiffraction under high pressure, suggesting the high enough energyto cause modulation of the planarity in terms of the Landau-de Gennesfree energy of isolated P3HT chains as 0.23 kJ mol–1. In contrast, the P3HT:PCBM blend showed a simple decrease in photoconductivityirrespective of the identical compressive behavior of P3HT. A mechanisticinsight into the interplay of intra- and intermolecular mobilitiesis a key to tailoring the dynamic π-figuration associated withelectrical properties, which may lead to the use of HP-TRMC for exploringdivergent π-conjugated materials at the desired molecular arrangementand conformation. [ABSTRACT FROM AUTHOR]

Organic field-effect transistors(OFETs) are receiving an increasedamount of attention because of their intriguing advantages such asflexibility, low cost, and solution processability. Development oforganic conjugated polymers with balanced ambipolar carrier transportationoperated under ambient conditions, in particular, is considered tobe one of the central issues in OFETs. In this work, the 3,7-bis[(E)-2-oxoindolin-3-ylidene]-3,7-dihydrobenzo[1,2-b:4,5-b′]difuran-2,6-dione (BDOPV)unit as a good acceptor unit was copolymerized with three donor moieties,thieno[3,2-b]thiophene (TT), benzo[1,2-b:4,5-b′]dithiophene (BDT), and benzo[1,2-b:4,5-b′]diselenophene (BDSe), toconstruct three donor–acceptor (D–A) conjugated polymers, BDOPV–TT, BDOPV–BDT, and BDOPV–BDSe. Photophysical and electrochemical propertiesof all the polymers were characterized. The fabrication of OFETs usingthree polymers as the active layers demonstrated that all the threepolymers showed balanced ambipolar transport properties tested underambient conditions, which is of great importance in complementarycircuits. In particular, both electron and hole mobilities of BDOPV–TTwere achieved above 1 cm2V–1s–1under ambient conditions (1.37and 1.70 cm2V–1s–1, respectively), showing great potential in balanced ambipolar OFETs. [ABSTRACT FROM AUTHOR]

In this Perspective, we make thecase that the biological applicationsof organic semiconductor devices are significant. Indeed, we arguethat this is an arena where organic materials have an advantage comparedto traditional electronic materials, such as silicon. By discussingthe physical structure and morphology of conjugated polymers, we areable to emphasize the key properties that make organic materials idealfor bioelectronics applications. We highlight a few recent devicesthat show either unique features or exceptionally high performance.On the basis of these examples, we discuss the future trajectory ofthis emerging field, note areas where further research is needed,and suggest possible applications in the short term. [ABSTRACT FROM AUTHOR]

Ordered structures of self-assembledblock copolymers (BCPs) wouldbe the ideal active-layer candidates for high-performance organicelectronics. However, fabrication of such structures from BCPs ofconjugated polymers has been very limited due to the strong rod–rodinteractions between the conjugated blocks, which inhibit the formationof ordered structures. Here, we developed a novel molecular designof conjugated polymer-based graft copolymers to control the rigidityof the copolymers and to produce a variety of ordered nanostructures.A series of well-defined poly(3-hexylthiophene)-graft-poly(2-vinylpyridine) (P3HT-g-P2VP) copolymerswere prepared via controlled polymerization, followed by microwave-assistedclick reaction. We observed that controlling the molecular weights(Mn) of the grafted P2VP chains allowedus to regulate the rod–rod interaction of the copolymers systematically,as evidenced by differential scanning calorimetry and X-ray scatteringmeasurements. As the Mnof the graftedP2VP chains increased, the crystallinity of the P3HT block in thecopolymers gradually decreased so that the enthalpic interaction betweenP3HT and P2VP chains became more dominant than the rod–rodinteraction of the P3HT moiety. Therefore, we produced thermally annealed,well-ordered nonfibril nanostructures of P3HT-based copolymers, includinglamellae, hexagonally packed cylinders, and spheres. [ABSTRACT FROM AUTHOR]

The chain shape of polymers affects many aspects of theirbehavior and is governed by their intramolecular interactions. Delocalizationof electrons along the backbone of conjugated polymers has been shownto lead to increased chain rigidity by encouraging a planar conformation.Poly(3-hexylthiophene) and other poly(3-alkylthiophenes) (P3ATs) areinteresting for organic electronics applications, and it is clearthat a hierarchy of structural features in these polymers controlscharge transport. While other conjugated polymers are very rigid,the molecular structure of P3AT allows for two different planar conformationsand a significant degree of torsion at room temperature. It is unclear,however, how their chain shape depends on variables such as side chainchemistry or regioregularity, both of which are key aspects in themolecular design of organic electronics. Small-angle neutron scatteringfrom dilute polymer solutions indicates that the chains adopt a randomcoil geometry with a semiflexible backbone. The measured persistencelength is shorter than the estimated conjugation length due to thetwo planar conformations that preserve conjugation but not backbonecorrelations. The persistence length of regioregular P3HT has beenmeasured to be 3 nm at room temperature and decreases at higher temperatures.Changes in the regioregularity, side chain chemistry, or syntheticdefects decrease the persistence length by 60–70%. [ABSTRACT FROM AUTHOR]

Solution-processable semiconducting copolymers, poly[N-9′-heptadecanyl-2,7-carbazole-alt-5,5′-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)](PCDTBT) and poly[4,8-bis(2-ethylhexyl-2-thenyl)-benzo[1,2-b:4,5-b′]dithiophene-alt-5,5′-(4′,7′-di-2-thienyl-2′,1′,3′-benzothiadiazole)](PBDTDTBT), and their pyrene-containing terpolymers were synthesizedusing Suzuki or Stille coupling. Pyrene units were introduced to improvethe charge-transporting abilities of the polymers. The resulting polymerswere found to be soluble in common organic solvents and formed smoothand uniform spin-coated thin films. They also exhibited good thermalstability and lost <5% of their weight upon heating to ∼350°C. Solution-processed field-effect transistors fabricated usingthese polymers showed p-type organic thin-film transistor characteristics.The pyrene-containing terpolymers showed higher field-effect mobilitiesthan their corresponding parent polymers, and their mobility increasedwith increasing pyrene content. Furthermore, they had lower HOMO energylevels than the corresponding PCDTBT or PBDTDTBT polymers. Bulk heterojunctionsolar cells with an ITO/PEDOT:PSS/polymer:PC71BM/Ca/Alconfiguration fabricated using the pyrene-containing polymers hadhigher power conversion efficiencies than those using the correspondingparent polymers. [ABSTRACT FROM AUTHOR]

The uniformity of operating parameters in organic nonvolatile memory devices is very important to avoid false programming and error readout problems. In the present work, we fabricated an organic resistive-switching memory based on protonic-acid-doped polyazomethine (PA-TsOH), which demonstrates an excellent operative uniformity and multilevel storage capability. The deliberate tuning of the resistance states can be attributed to the electric-field-controlled molecular doping of the imine-containing polymers. [ABSTRACT FROM AUTHOR]

Conjugated polymers and small molecules containing thenonplanararomatic 1,6-methano[10]annulene were synthesized in an effort tounderstand how torsional differences between planar and nonplanarπ-electron components influence the electronic properties ofπ-conjugated materials. The polymers and small molecule modelsystems contain commonly employed aromatic subunits such as thiophene,diketopyrrolopyrrole, and 2,1,3-benzothiadiazole, leading to electrondonor and donor–acceptor polymers. The curved geometry of 1,6-methano[10]annulenecan lead to reduced local torsional strain in semiconducting polymersrelative to large planar aromatics, potentially increasing intrapolymerconjugation. The relative amount of effective conjugation length increasegranted by the annulene in each system of regioisomers was interrogatedthrough the use of UV–vis and photoluminescence spectroscopyand electrochemistry, and it was found that 1,6-methano[10]annulenerelieves some torsional strain associated with solubilizing alkylchains clashing with aromatic rings along the polymer backbone. Thepolymers were also found to be highly disordered in thin films yetstill provided reasonable hole mobilities (ca. 10–4cm2/(V s)) in OFET devices. These results suggest thatmethano[10]annulene or other curved aromatics may prove useful inthe future development of organic electronics. [ABSTRACT FROM AUTHOR]

An electrically percolated network structure of conjugatedpolymers is critical to the development of organic electronics. Herein,we investigate the potential to rationally design an interconnectednetwork of conjugated polymers using the gelation of poly(3-hexylthiophene)(P3HT) as a model system. The three-dimensional network structureis evaluated through small-angle neutron scattering (SANS) and ultrasmall-angleneutron scattering (USANS). The analytical models used for data fittingprovide relevant structural parameters over multiple length scales.Structural parameters include the fiber cross section (height andwidth), the specific surface area, and the network density (i.e.,fractal dimension). Simultaneous rheological and conductivity measurementsalso provide insight into the development of the mechanical and electricalproperties of organogels and allow us to propose a detailed gelationmechanism for P3HT. The fiber shape is found to be relatively independentof the solvent type, but P3HT organogels show distinct differencesin conductivity, which can be directly linked to differences in thebranching network structures. These results suggest that the gelationof fiber-forming conjugated polymers offers an excellent platformfor designing electrically percolated networks that can be used forstructural optimization in organic electronic devices. [ABSTRACT FROM AUTHOR]

Conjugated polymers with nearly planar backbones have been the most commonly investigated materials for organic-based electronic devices. More twisted polymer backbones have been shown to achieve larger open-circuit voltages in solar cells, though with decreased short-circuit current densities. We systematically impose twists within a family of poly(hexylthiophene)s and examine their influence on the performance of polymer:fullerene bulk heterojunction (BHJ) solar cells. A simple chemical modification concerning the number and placement of alkyl side chains along the conjugated backbone is used to control the degree of backbone twisting. Density functional theory calculations were carried out on a series of oligothiophene structures to provide insights on how the sterically induced twisting influences the geometric, electronic, and optical properties. Grazing incidence X-ray scattering measurements were performed to investigate how the thin-film packing structure was affected. The open-circuit voltage and charge-transfer state energy of the polymer:fullerene BHJ solar cells increased substantially with the degree of twist induced within the conjugated backbone—due to an increase in the polymer ionization potential—while the short-circuit current decreased as a result of a larger optical gap and lower hole mobility. A controlled, moderate degree of twist along the poly(3,4-dihexyl-2,2′:5′,2″-terthiophene) (PDHTT) conjugated backbone led to a 19% enhancement in the open-circuit voltage (0.735 V) vs poly(3-hexylthiophene)-based devices, while similar short-circuit current densities, fill factors, and hole-carrier mobilities were maintained. These factors resulted in a power conversion efficiency of 4.2% for a PDHTT:[6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) blend solar cell without thermal annealing. This simple approach reveals a molecular design avenue to increase open-circuit voltage while retaining the short-circuit current. [ABSTRACT FROM AUTHOR]

Identifying structure formation in semicrystalline conjugated polymers is the fundamental basis to understand electronic processes in these materials. Although correlations between physical properties, structure formation, and device parameters of regioregular, semicrystalline poly(3-hexylthiophene) (P3HT) have been established, it has remained difficult to disentangle the influence of regioregularity, polydispersity, and molecular weight. Here we show that the most commonly used synthetic protocol for the synthesis of P3HT, the living Kumada catalyst transfer polycondensation (KCTP) with Ni(dppp)Cl2 as the catalyst, leads to regioregular chains with one single tail-to-tail (TT) defect distributed over the whole chain, in contrast to the hitherto assumed exclusive location at the chain end. NMR end-group analysis and simulations are used to quantify this effect. A series of entirely defect-free P3HT materials with different molecular weights is synthesized via new, soluble nickel initiators. Data on structure formation in defect-free P3HT, as elucidated by various calorimetric and scattering experiments, allow the development of a simple model for estimating the degree of crystallinity. We find very good agreement for predicted and experimentally determined degrees of crystallinities as high as 70%. For Ni(dppp)Cl2-initiated chains comprising one distributed TT unit, the comparison of simulated crystallinities with calorimetric and optical measurements strongly suggests incorporation of the TT unit into the crystal lattice, which is accompanied by an increase in backbone torsion. Polydispersity is identified as a major parameter determining crystallinity within the molecular weight range investigated. We believe that the presented approach and results not only contribute to understanding structure formation in P3HT but are generally applicable to other semicrystalline conjugated polymers as well. [ABSTRACT FROM AUTHOR]

Conjugated polymers, in general, are unstable when exposedto air,solvent, or thermal treatment, and these challenges limit their practicalapplications. Therefore, it is of great importance to develop newmaterials or methodologies that can enable organic electronics withair stability, solvent resistance, and thermal stability. Herein,we have developed a simple but powerful approach to achieve solvent-resistantand thermally stable organic electronic devices with a remarkablyimproved air stability, by introducing an azide cross-linkable groupinto a conjugated polymer. To demonstrate this concept, we have synthesizedpolythiophene with azide groups attached to end of the alkyl chain(P3HT-azide). Photo-cross-linking of P3HT-azide copolymers dramaticallyimproves the solvent resistance of the active layer without disruptingthe molecular ordering and charge transport. This is the first demonstrationof solvent-resistant organic transistors. Furthermore, the bulk-heterojunctionorganic photovoltaics (BHJ OPVs) containing P3HT-azide copolymersshow an average efficiency higher than 3.3% after 40 h annealing atan elevated temperature of 150 °C, which represents one of themost thermally stable OPV devices reported to date. This enhancedstability is due to an in situ compatibilizer that forms at the P3HT/PCBMinterface and suppresses macrophase separation. Our approach pavesa way toward organic electronics with robust and stable operations. [ABSTRACT FROM AUTHOR]

Through a rational design, a novel Donor–Acceptor π-conjugated (D-π-A) blue fluorescent indenofluorene dye, DA-DSF-IF, has been synthesized for application in single-layer Small Molecule Organic Light Emitting Diodes (SMOLEDs). This new blue emitter possesses bipolar properties as well as good morphological and emission color stabilities and has been successfully used in a blue emitting single-layer SMOLED, with performances impressively magnified compared to a nonbipolar indenofluorene emitter. [ABSTRACT FROM AUTHOR]

To improve both the stability and the efficiency of single spin-coatable active-layer polymer light emitting devices based on fluorene (F) and benzothidiazole (BT), that is, two of the monomers employed as building units in the most efficient electroluminescent polymers commonly used in organic electronics, we carry out a dual strategy. We prepare a triphenylamino (TPA) disubstituted F in order to improve hole injection, prevent oxidation and aggregation and we exploit the mechanism of resonant energy transfer through the macromolecular approach of a rod−rod-type all conjugated diblock copolymer formed by an alternated copolymer of TPA disubstituted F with dialkylsubstituted F (poly[(9,9-di-n-hexylfluorene)-alt-(9,9-bis(4-diphenylaminophenyl)-fluorene]) and an alternated copolymer between BT and F (poly(9,9′-dioctylfluorene-alt-benzothiadiazole). We show that, by changing the relative length of the two blocks, we are able to address the electrooptical properties thanks to a different supramolacular organization, which can be governed by a proper chemical design, and the energy transfer mechanism tunability. The device performance and color coordinates are controlled by both the suppression of oxidation processes and the high thermal stability of the copolymers which allow stable green HDTV standard-matching electroluminescence to be obtained at ambient conditions for several hours. Two different copolymers are studied: a diblock amorphous copolymer and a more crystalline one. A further increase of the external quantum efficiency up to 5.5%, a luminous efficiency of 22.5 cd/A with a luminance of above 50 000 cd/m2, is obtained by the improvement of the cathode/polymer interfacial adhesion in the former copolymer upon thermal treatment above the glass transition temperature of PF8BT. On the contrary, the same treatment on the latter compound is detrimental (charge carrier unbalancing) due to a further increase of the crystallinity. The insertion of a poly(N-vinylcarbazole) interlayer prevents exciton quenching at the PEDOT:PSS interface. [ABSTRACT FROM AUTHOR]

Conjugated polymers derived from thiophene or 3,4-ethylenedioxythiophene derivatives have been widely investigated for use in organic thin-film transistors and organic photovoltaic devices. We describe here the synthesis of a series of conjugated microporous polymers formed by reaction of spiro-bis(2,5-dibromopropylenedioxythiophene) with one of three di- or triethynyl monomers. These polymers have surface areas up to 1631 m2/g and exhibit significant microporosity, suggesting possible applications in the fields of organic electronics or optoelectronics. [ABSTRACT FROM AUTHOR]

Single-molecule spectroscopy can help to uncover the underlying heterogeneity of conjugated polymers used in organic electronics, revealing the most effective molecules in an ensemble in terms of the transport of charge and excitation energy. We demonstrate that β-phase polyfluorene chains can form a near-perfect π-electron system, whereas conventional polymers exhibit chromophoric localization due to perturbation of the conjugation. Broad-band excitation spectroscopy demonstrates that only one absorbing and emitting unit is present on the polymer chain with an average length of ~500 repeat units, illustrating that the material effectively behaves as a molecular quantum wire with strong electronic coupling throughout the entire system. [ABSTRACT FROM AUTHOR]

The article provides information on the chain-length dependent nematic ordering of conjugated polymers within a liquid crystal solvent. Accordingly, the said polymer activity plays a significant role in performance improvement of organic electronic devices, using a long-range supramolecular interactions to establish organized self-assembled structures. However, it is not well-fixed on how long the polymer solute has to be to go through improved ordering.