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Fully π-conjugated polymers with rigid aromatic units are promising for flexible optoelectronic devices, but their inherent brittleness poses a challenge for achieving high-performance, intrinsically stretchable fully π-conjugated polymer. Here, we are establishing an external-plasticizing strategy using semiconductor fluid plasticizers (Z1 and Z2) to enhance the optoelectronic, morphological, and stretchable properties of fully π-conjugated polymer films for flexible light-emitting diodes. The synergistic effect of hierarchical structure and optoelectronic properties of Z1 in poly(9,9-di-n-octylfluorene-alt-benzothiadiazole) (F8BT) films enable excellent stretchable deformability (~25%) and good conductivity. PLEDs based on F8BT/Z1 films show stable electroluminescence and efficiency under 15% stretch and 100 cycles at 10% strain, revealing outstanding stress tolerance. This strategy is also improving the stretchable properties of polymers like poly(9,9-di-n-octylfluorenyl-2,7-diyl) (PFO) and poly(2-methoxy-5(2′-ethyl)hexoxy-phenylenevinylene) (Super Yellow), demonstrating its general applicability. Therefore, this strategy can provide effective guidance for designing high-performance stretchable fully π-conjugated polymers films for flexible electronic devices. The realization of intrinsically stretchable fully π-conjugated polymer film is challenging due to their inherent brittle nature. Here, authors apply semiconductor fluid molecular plasticizers to improve stretchable deformability, achieving high performance flexible polymer light-emitting diodes. [ABSTRACT FROM AUTHOR]

Organic electrochemical transistors (OECTs) possess low operating voltage and excellent amplification capability and show promising applications in biosensors and flexible electronics. However, the active layers of OECTs are usually dense films, which show limited ion penetration/transport, resulting in limited performances of OECTs. Here, unprecedented high‐performance flexible multifunctional OECTs based on nanoporous (mainly 2–60 nm), high‐specific‐surface‐area (255–281 m2 g−1), and flexible conjugated polymer aerogel films are developed. The nanoporous structures effectively facilitate ion penetration/transport, leading to significantly enhanced transconductance (48.5–53.5 mS) and on/off ratio (6.4 × 104) of the OECTs compared with those of dense devices. The resulting OECT‐based glucose sensors exhibit an ultralow detection limit of 1 pm, approximately two to three orders of magnitude lower than those of the previously reported OECT glucose sensors, and an ultrabroad detection range of 1 pm–5 m. They can detect trace amounts of glucose in sweat, serum, saliva, and urine in real time. Moreover, the OECTs can be used for high‐performance flexible artificial synapses and electrocardiogram monitoring. This work provides a powerful strategy toward highly sensitive biosensors, artificial synapses, and electrophysiological signal monitoring. [ABSTRACT FROM AUTHOR]

Conjugated polymers consist of complex backbone structures and side‐chain moieties to meet various optoelectronic and processing requirements. Recent work on conjugated polymers has been devoted to studying the mechanical properties and developing new conjugated polymers with low modulus and high‐crack onset strain, while the thin film mechanical stability under long‐term external tensile strain is less investigated. Here we performed direct mechanical stress relaxation tests for both free‐standing and thin film floated on water surface on both high‐Tg and low‐Tg conjugated polymers, as well as a reference nonconjugated sample, polystyrene. We measured thin films with a range of film thickness from 38 to 179 nm to study the temperature and thickness effect on thin film relaxation, where an apparent enthalpy–entropy compensation effect for glassy polymer PS and PM6 thin films was observed. We also compared relaxation times across three different conjugated polymers and showed that both crystalline morphology and higher modulus reduce the relaxation rate besides higher glass transition temperature. Our work provides insights into the mechanical creep behavior of conjugated polymers, which will have an impact on the future design of stable functional organic electronics. [ABSTRACT FROM AUTHOR]

For advancing next‐generation optoelectronics, a versatile strategy for fabricating π‐conjugated polymer (π‐CP)/chiral‐small molecule (SM) hybrid films through co‐crystallization‐mediated chirality transfer is reported. The transfer of optical chirality from 1,1′‐binaphthyl–2,2′‐diamine (BN), a representative chiral inducer SM, to thin films of various achiral π‐CPs, including non‐fluorene π‐CPs, is achieved by simply blending the π‐CPs with BN using aromatic organic solvents. The resulting π‐CP/chiral‐SM hybrid films exhibit chiroptical responses at the main electronic absorption bands of various π‐CPs. Studies of the morphology, crystalline structure, and phase‐separation structure of a representative hybrid system of poly(3‐hexylthiophene) (P3HT) and BN reveal that these hybrid films exhibit a characteristic lamellar structure where the π‐CPs co‐crystallize with chiral BN molecules, facilitated by aromatic solvent‐assisted intermolecular π–π interactions. In‐depth photophysical analysis suggests that BN molecules co‐crystallized in the P3HT lamellar structure induce asymmetrically misaligned transition dipoles along the P3HT conjugated backbone, transferring optical chirality from BN to P3HT under circularly polarized light illumination. As a proof‐of‐concept, chiroptical photodiodes based on π‐CP/chiral‐SM hybrid films and printed micropatterns, exhibiting a distinguishable photocurrent response depending on the direction of circularly polarized light are successfully demonstrated. [ABSTRACT FROM AUTHOR]

Heavy atoms can form highly coordinated states, and their optical properties have attracted much attention. Recently, we have demonstrated that a reversible coordination-number shift of hypervalent tin(IV) from five to six can provide predictable hypsochromic shifts in light absorption and emission properties in small molecules and a π-conjugated polymer film. Herein, we show the preparation of seven-coordinated tin and reveal that the binding constant of the seven coordination with ethylenediamine (EDA, K = 2900 M−1) is 200 times higher than that of six coordination with propylamine (PA, K = 14 M−1) owing to the chelate effect. Moreover, reversible vapochromism of the π-conjugated polymer film was observed upon exposure (λabs = 598 nm and λPL = 697 nm) and desorption (λabs = 641 nm and λPL = 702 nm) of EDA vapor. Furthermore, as a unique demonstration, the thermochromic film was prepared by fixing the seven coordination as the initial state using 1,10-phenanthroline. These optical variations are predictable by quantum chemical calculations. Our findings are valuable for the development of designable and controllable stimuli-responsive materials focusing on the inherent properties of the elements. [ABSTRACT FROM AUTHOR]

The aggregation morphologies of conjugated polymers in solutions and solid films are important for their optoelectronic applications. Due to the amorphous state of the polymers, it remains a great challenge to determine their conformations in either liquids or solids. Herein, a ps/fs synchronized 2D IR technique is applied to investigate the molecular conformations of a high-mobility n-type low-bandgap copolymer, N2200, dissolved in CHCl3 and CCl4, and in solid films cast from both solutions by the vibrational cross-angle method. In CCl4, the polymer forms more aggregates and folds more and the backbone dihedral angle of C–C(NDI)/C–S(Thiophene) of its average conformation is about 10° more distorted than that in CHCl3 and the most stable conformation for a free molecule. Anti-intuitively, the solid films cast from both solutions have the same molecular conformation, and the conformation is similar to that of the polar CHCl3 rather than the conformation of the less polar CCl4. The results imply that the interaction between the polymer backbones is probably stronger than its interaction with CCl4, which can naturally guide the rearrangement of polymer chains during the evaporation of solvent molecules. This work also implies that the balance and competition between the polymer/polymer interaction and the polymer/solvent interaction seem to be the dominant factors responsible for what morphology can form in a solid film cast from solution. It is not always true that different molecular conformations must exist in solid films grown from different solutions with different polarity or different extents of aggregates with different conformations. [ABSTRACT FROM AUTHOR]

Donor–acceptor (D‐A) conjugated polymers have demonstrated great potential in organic field‐effect transistors application, and their aggregated structure is a crucial factor for high charge mobility. However, the aggregated structure of D‐A conjugated polymer films is complex and the structure–property relationship is difficult to understand. This review provides an overview of recent progress in controlling the aggregated structure of D‐A conjugated polymer films for higher mobility, including the mechanisms, methods, and properties. We first discuss the multilevel microstructures of D‐A conjugated polymer films, and then summarize the current understanding of the relationship between film microstructures and charge transport properties. Subsequently, we review the theory of D‐A conjugated polymer crystallization. After that, we summarize the common methods to control the aggregated structure of semi‐crystalline and near‐amorphous D‐A conjugated polymer films, such as crystallites and aggregates, tie chains, film alignment, and attempt to understand them from the basic theory of polymer crystallization. Finally, we provide the current challenges in controlling the aggregated structure of D‐A conjugated polymer films and in understanding the structure–property relationship. [ABSTRACT FROM AUTHOR]

High-quality conjugated microporous polymer (CMP) films with orientation and controlled structure are extremely desired for applications. Here, we report the effective construction of CMP 3D composite films (pZn/PTPCz) with a controlled porosity structure and preferred orientation using the template-assisted electropolymerization (EP) approach for the first time. The structure of pZn/PTPCz composite thin films and nitrophenol sensing performance were thoroughly studied. When compared to the control CMP film made on flat indium tin oxide (ITO) substrates, the as-prepared pZn/PTPCz composite films showed significantly enhanced fluorescent intensity and much better sensing performance for the model explosive. This was attributed to the metal-enhanced fluorescence (MEF) of porous nanostructured zinc (pZn) and the additional macroporosity of the pZn/PTPCz composite films. This work provides a feasible approach for creating oriented 3D CMP-based thin films for advanced applications. [ABSTRACT FROM AUTHOR]

Conjugated polymers have demonstrated promising optoelectronic properties, but their brittleness and poor mechanical characteristics have hindered their fabrication into durable fibers and textiles. Here, we report a universal approach to continuously producing highly strong, ultratough conjugated polymer fibers using a flow-enhanced crystallization (FLEX) method. These fibers exhibit one order of magnitude higher tensile strength (>200 megapascals) and toughness (>80 megajoules per cubic meter) than traditional semiconducting polymer fibers and films, outperforming many synthetic fibers, ready for scalable production. These fibers also exhibit unique strain-enhanced electronic properties and exceptional performance when used as stretchable conductors, thermoelectrics, transistors, and sensors. This work not only highlights the influence of fluid mechanical effects on the crystallization and mechanical properties of conjugated polymers but also opens up exciting possibilities for integrating these functional fibers into wearable electronics. [ABSTRACT FROM AUTHOR]

Thin films of conjugated polymer and enzyme can be used to unravel the interaction between components in a biosensor. Using artificial neural networks (ANNs) improves data interpretability and helps construct models with great capacity for classifying and processing information. The present work used kinetic data from the catalytic activity of urease immobilized in different conjugated polymers to create ANN models using time, substrate concentration, and absorbance as input variables since the models had absorbance in a posterior instant as output value to explore the predictivity of the ANNs. The performance of the models was evaluated by Pearson's correlation coefficient (ρ) and mean squared error (MSE) values. After the learning process, a series of new experiments were performed to verify the generality of the models. As the main results, the best ANN model presented 0.9980 and 3.0736 × 10–5 for ρ and MSE, respectively. For the simulation step, intermediary values of substrate concentration were used. The mean absolute percentage error (MAPE) values were 3.34, 3.07, and 3.78 for 12 mM, 22 mM, and 32 mM concentrations, respectively. Overall, with the simulations, it was possible to ascertain the interpolatory capacity of the model, which has a learning mechanism based on absorbance and time as variables. Thus, the potential of ANNs would be in their use in pre-evaluations, helping to determine the substrate concentration at which there is higher catalytic activity or in determining the linear range of the sensor. [ABSTRACT FROM AUTHOR]

The physical blending of high‐mobility conjugated polymers with ductile elastomers provides a simple way to realize high‐performance stretchable films. However, how to control the morphology of the conjugated polymer and elastomer blend film and its response to mechanical fracture processes during stretching are not well understood. Herein, a sandwich structure is constructed in the blend film based on a conjugated polymer poly[(5‐fluoro‐2,1,3‐benzothiadiazole‐4,7‐diyl)(4,4‐dihexadecyl‐4H‐cyclopenta[2,1‐b:3,4‐b″]dithiophene‐2,6‐diyl)(6‐fluoro‐2,1,3‐benzothiadiazole‐4,7‐diyl)(4,4‐dihexadecyl‐4H‐cyclopenta[2,1‐b:3,4‐b″]dithiophene‐2,6‐diyl)] (PCDTFBT) and an elastomer polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SEBS). The sandwich structure is composed of a PCDTFBT:SEBS mixed layer laminated with a PCDTFBT‐rich layer at both the top and bottom surfaces. During stretching, the external strain energy can be effectively dissipated by the deformation of the crystalline PCDTFBT domains and amorphous SEBS phases and the recrystallization of the PCDTFBT chains. This endows the blend film with excellent ductility, with a large crack onset strain exceeding 1100%, and minimized the electrical degradation of the blend film at a large strain. This study indicates that the electrical and mechanical performance of conjugated polymer/elastomer blend films can be improved by manipulating their microstructure. [ABSTRACT FROM AUTHOR]

Up to now, researches on the mobility–stretchability of semiconducting polymers are extensively investigated, but little attention was paid to their morphology and field‐effect transistor characteristics under compressive strains, which is equally crucial in wearable electronic applications. In this work, a contact film transfer method is applied to evaluate the mobility–compressibility properties of conjugated polymers. A series of isoindigo–bithiophene conjugated polymers with symmetric carbosilane side chains (P(SiSi)), siloxane‐terminated alkyl side chains (P(SiOSiO)), and combined asymmetric side chains (P(SiOSi)) are investigated. Accordingly, a compressed elastomer slab is used to transfer and compress the polymer films by releasing prestrain, and the morphology and mobility evolutions of these polymers are tracked. It is found that P(SiOSi) outperforms the other symmetric polymers including P(Si─Si) and P(SiO─SiO), having the ability to dissipate strain with its shortened lamellar spacing and orthogonal chain alignment. Notably, the mechanical durability of P(SiOSi) is also enhanced after consecutive compress–release cycles. In addition, the contact film transfer technique is demonstrated to be applicable to investigate the compressibility of different semiconducting polymers. These results demonstrate a comprehensive approach to understand the mobility–compressibility properties of semiconducting polymers under tensile and compressive strains. [ABSTRACT FROM AUTHOR]

Fabrication of uniform and oriented thin films of conjugated polymers (CPs) with controlled thickness is essential for the implementation of organic devices. Over the years, unidirectional floating film transfer method (UFTM) has emerged as a facile technique for the fabrication of oriented thin films but its distribution of orientation in vertical (thickness) direction has not been explored yet. To investigate this, thin films of nonregioregular poly(3‐hexylthiophene) are fabricated using UFTM with different concentrations of CPs to obtain thickness variation from 11 to 47 nm. Thin films of 4% and 9% polymer solution have similar dichroic ratio of 5.5 but have an appreciable difference in film thickness of 12 and 47 nm where thicker films are disordered as probed by polarized absorption spectra. Organic field‐effect transistors fabricated using thinner films (12 nm) exhibit a saturated charge carrier mobility of 2.3 × 10−3cm2 V−1 s−1, an order of magnitude higher than its thicker (47 nm) counterpart. This difference in device performance can be attributed to the fact that charge transport is principally governed by the top polymer surface at air–polymer interface, which is found to be more disordered owing to the vertical distribution of orientation. [ABSTRACT FROM AUTHOR]

Wearable devices benefit from the use of stretchable conjugated polymers (CPs). Traditionally, the design of stretchable CPs is based on the assumption that a low elastic modulus (E) is crucial for achieving high stretchability. However, this research, which analyzes the mechanical properties of 65 CP thin films, challenges this notion. It is discovered that softness alone does not determine stretchability; rather, it is the degree of entanglement that is critical. This means that rigid CPs can also exhibit high stretchability, contradicting conventional wisdom. To inverstigate further, the mechanical behavior, electrical properties, and deformation mechanism of two model CPs: a glassy poly(3‐butylthiophene‐2,5‐diyl) (P3BT) with an E of 2.2 GPa and a viscoelastic poly(3‐octylthiophene‐2,5‐diyl) (P3OT) with an E of 86 MPa, are studied. Ex situ transmission X‐ray scattering and polarized UV–vis spectroscopy revealed that only the initial strain (i.e., <20%) exhibits different chain alignment mechanisms between two polymers, while both rigid and soft P3ATs showed similarly behavior at larger strains. By challenging the conventional design metric of low E for high stretchability and highlighting the importance of entanglement, it is hoped to broaden the range of CPs available for use in wearable devices. [ABSTRACT FROM AUTHOR]

The ubiquitous presence of per‐ and polyfluoroalkyl substances (PFAS) in aqueous environments has aroused societal concern. Nonetheless, effective sensing technologies for continuous monitoring of PFAS within water distribution infrastructures currently do not exist. Herein, we describe a ratiometric sensing approach to selectively detect aqueous perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) at concentrations of μg ⋅ L−1. Our method relies on the excitonic transport in a highly fluorinated poly(p‐phenylene ethynylene) to amplify a ratiometric emission signal modulated by an embedded fluorinated squaraine dye. The electronic coupling between the polymer and dye occurs through overlap of π‐orbitals and is designed such that energy transfer is dominated by an electron‐exchange (Dexter) mechanism. Exposure to aqueous solutions of PFAS perturbs the orbital interactions between the squaraine dye and the polymer backbone, thereby diminishing the efficiency of the energy transfer and producing a "polymer‐ON/dye‐OFF" response. These polymer/dye combinations were evaluated in spin‐coated films and polymer nanoparticles and were able to selectively detect PFAS at concentrations of ca. 150 ppb and ca. 50 ppb, respectively. Both polymer films and nanoparticles are not affected by the type of water, and similar responses to PFAS were found in milliQ and well water. [ABSTRACT FROM AUTHOR]

Rubbing‐induced alignment of conjugated polymers is systematically investigated in terms of intra‐ and inter‐molecular interaction. Various polymer films with a broad range of polymer chain rigidity are rubbed, and the degree of polymer chain alignment is quantitatively characterized. The rubbing technique effectively aligns crystalline domains in conjugated polymer films when the temperature approaches the critical rubbing temperature (Trc$T_{\mathrm{r}}^{\mathrm{c}}$), at which the rearrangement and the slip of polymer chains are possible. A polymer with significant intra‐/inter‐molecular interactions exhibits higher Trc$T_{\mathrm{r}}^{\mathrm{c}}$, though quantitative analysis reveals an intermediately aligned state at temperature Tr′ lower than Trc$T_{\mathrm{r}}^{\mathrm{c}}$. This state originates from polymer chain aggregation in an amorphous domain. The intermediately aligned state can be controlled by plasticizer, which enables low‐temperature alignment of high‐mobility polymer film by reducing Tr′ to near 100 °C, increases the crystallinity, and improves the alignment effect at this state comparable to that of the completely aligned state obtained at extremely high temperatures. [ABSTRACT FROM AUTHOR]

We report the use of poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) as a transducing material in the fabrication of mechanical-to-electrical conversion devices based on the flexoelectric-like response of this polymer. Devices are made in a cantilever-based three-layer stainless-steel/PEDOT:PSS/top metal electrode configuration to assess the effective transverse flexoelectric coefficient μ 12 ′ . We investigated the influence of the nature of the top electrode in the flexoelectric response comparing samples with gold and aluminum top electrodes and demonstrated the huge impact of adding a small fraction of a second dopant such as xylitol to the PEDOT:PSS polymer blend and the benefits of a post-treatment of the polymer film with ethanol and methanol on the flexoelectric coefficient. The combination of xylitol addition and the rinsing of the polymer films with ethanol and methanol, along with the use of gold as a top electrode, led to a significant improvement of μ 12 ′ to ca. 24 μC m−1, which is in the range of those reported for high permittivity oxide materials. These findings support the use of conjugated polymers as an alternative to inorganic materials in flexoelectric-based applications, where large flexibility is required. [ABSTRACT FROM AUTHOR]

Conjugated polymer films, which can conduct both ionic and electronic charges, are central to building soft electronic sensors and actuators. Despite the possible interplay between light absorption and the mixed conductivity of these materials in aqueous biological media, no single polymer film has been utilized to create a solar-switchable organic bioelectronic circuit that relies on a fully reversible and redox reaction-free potentiometric photodetection and current modulation. Here we demonstrate that the absorption of light by an electron and cation-transporting polymer film reversibly modulates its electrochemical potential and conductivity in an aqueous electrolyte, which is harnessed to design an n-type photo-electrochemical transistor (n-OPECT). By controlling the intensity of light incident on the n-type polymeric gate electrode, we generate transistor output characteristics that mimic the modulation of the polymeric channel current achieved through gate voltage control. The micron-scale n-OPECT exhibits a high signal-to-noise ratio and an excellent sensitivity to low light intensities. We demonstrate three direct applications of the n-OPECT, i.e., a photoplethysmogram recorder, a light-controlled inverter circuit, and a light-gated artificial synapse, underscoring the suitability of this platform for a myriad of biomedical applications that involve light intensity changes. Many phototransistors are multi-component systems with inorganic materials or involve faradaic processes that can be irreversible. Using a single photoactive polymer, Druet et al. report a reversible, water-compatible n-type photoelectrochemical transistor with potentiometric photodetection and current modulation. [ABSTRACT FROM AUTHOR]

Facile and efficient synthesis of conjugated donor-acceptor polymers via direct C-H arylation polymerization has received significant interest in organic electronic applications. We report here a one-pot synthesis of a series of bis(thiophen-2-yl)benzothiadiazole-based donor-acceptor polymers P1-4 via direct C-H arylation polymerization in excellent yield. Two donor moieties [3-hexylthiophene and 1,4-bis(dodecyloxy)benzene], and one acceptor unit 4,7-bis(thiophen-2-yl)benzo[c][1,2,5]thiadiazole were used for direct C-H arylation polymerization. The prowess of the methodology was applied to synthesis of polymer by adding one donor unit followed by a second donor unit after the due course. The resulting polymers are soluble and characterized. Optical and electrochemical properties were carried out by UV-Vis-NIR and cyclic voltammetry, respectively. A temperature-dependent absorption of the polymer films blended with PC71BM was studied for photovoltaic application. Devices were fabricated by solution-processable deposition of active layer and a PCE of 3.82% was achieved. [ABSTRACT FROM AUTHOR]

Semiconducting conjugated polymers bearing glycol side chains can simultaneously transport both electronic and ionic charges with high charge mobilities, making them ideal electrode materials for a range of bioelectronic devices. However, heavily glycolated conjugated polymer films have been observed to swell irreversibly when subjected to an electrochemical bias in an aqueous electrolyte. The excessive swelling can lead to the degradation of their microstructure, and subsequently reduced device performance. An effective strategy to control polymer film swelling is to copolymerize glycolated repeat units with a fraction of monomers bearing alkyl side chains, although the microscopic mechanism that constrains swelling is unknown. Here we investigate, experimentally and computationally, a series of archetypal mixed transporting copolymers with varying ratios of glycolated and alkylated repeat units. Experimentally we observe that exchanging 10% of the glycol side chains for alkyl leads to significantly reduced film swelling and an increase in electrochemical stability. Through molecular dynamics simulation of the amorphous phase of the materials, we observe the formation of polymer networks mediated by alkyl side-chain interactions. When in the presence of water, the network becomes increasingly connected, counteracting the volumetric expansion of the polymer film. [ABSTRACT FROM AUTHOR]

Bismuth vanadate (BiVO4) has been considered a promising photoactive material in photoelectrochemical (PEC) water-splitting systems. However, the performance of BiVO4-based photoanodes is currently unsatisfactory, indicating the need for new architectural designs to improve their efficiency. In this paper, a porphyrin-phosphazene polymer (THPP-HCCP) was synthesized with a sizeable conjugated structure, and Ag particles were deposited on its surface as an organic–inorganic composite interface improvement layer. The deposition of the composite polymer film on BiVO4 resulted in a significant increase in photocurrent density, reaching up to 2.2 mA cm−2 (1.23 V vs. RHE), almost three times higher than pristine BiVO4, which benefits from the synergistic effect of Ag nanoparticles and porphyrin-phosphazene. Furthermore, photophysical and intensity-modulated photocurrent analysis demonstrated that the Ag–THPP-HCCP heterostructures could broaden the light-absorbing range and facilitate hole transfer to the semiconductor surface, resulting in an improved water oxidation process. The dynamic charge transport behavior of Ag–THPP-HCCP/BiVO4 was investigated using scanning photoelectrochemical microscopy, which showed that the rate constant (Keff) exhibits an almost 4-fold increase compared to pristine BiVO4, indicating a significant improvement in the transport of photogenerated holes. This experiment presents a novel strategy for designing high-efficiency polymer-based photoanodes. [ABSTRACT FROM AUTHOR]

Porous films offer a general and simple strategy for balancing the electron/hole transport, and ion doping/dedoping process in organic electrochemical transistor (OECT) channel. Here a universal 3D integrated approach that simultaneously achieves both enhanced transconductance (gm) and mechanical stretchability via constructing a multilayer breath‐figured porous polymer channel by poly(3‐hexylthiophene) (P3HT)/ polystyrene‐block‐poly(ethylene‐ran‐butylene)‐block‐polystyrene (SEBS) and poly(2,5‐bis(3‐triethyleneglycoloxythiophen‐2‐yl)‐co‐thiophene) (Pg2T‐T)/SEBS mixture is demonstrated. The formed multilayer elastic porous structure provides efficient and tunable ionic‐electronic coupling and transport pathways, while also introducing immunity toward mechanical tensile deformation. Remarkably, an obvious increase in gm [from 10.05 mS (2.13 mS) to 29.23 mS (7.38 mS) for Pg2T‐T (P3HT)] is acquired by assembling the OECT porous channel from a single layer to a 3D trilayer. Moreover, mechanical stretchability as high as 40% for Pg2T‐T and 60% for P3HT, is obtained with >21% gm retained. Furthermore, high gms (9.34 mS and 0.92 mS for Pg2T‐T and P3HT, respectively) are maintained after 600 stretching cycles (20% and 30% tensile strains for Pg2T‐T and P3HT, respectively). Overall, the 3D porous structure provides an effective strategy to enhance stretchability and electrical performance for OECTs, as well as opens possibilities for other electronics where both stretchability and a large surface‐to‐volume ratio are needed. [ABSTRACT FROM AUTHOR]

We have used absorption, photoluminescence (PL), and variable angle spectroscopic ellipsometry (VASE) measurements to investigate the structural changes that take place upon high temperature annealing in spin-coated films of the prototypical conjugated polymer (CP) poly[2-(2′-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] (MEH-PPV). Absorption and VASE measurements reveal that the birefringence of the films increases by approximately a factor of two upon heating, which indicates a significant increase in the alignment of the conjugated polymer (CP) strands within the film plane. Absorption and PL spectra indicate the formation in annealed films of interchain species having lower energy transitions. But these measurements alone do not reveal the type of interchain species formed, such as excimers or aggregates. VASE measurements were used to investigate this feature and clearly reveal a new, low energy, feature with a shoulder at 650 nm in the dispersion relations of the extraordinary (out-of-plane) extinction and absorption coefficients of the annealed films, which we assign to aggregate absorption. Thus, our work shows that VASE is sufficiently sensitive to measure aggregate absorption in CP films. In the case of the ordinary (in-plane) extinction and absorption coefficients, there is an increased amplitude of the lower energy peak upon heating, owing to increased uniaxial anisotropy, along with a broadening and a longer red tail, but the well-resolved red-shifted absorption band seen for the extraordinary absorption coefficient is not observed. Therefore, we conclude that while in-plane and out-of-plane aggregation occurs in annealed spin-coated films of MEH-PPV, aggregate absorption is only clearly observed when the aggregate electronic transition dipole is oriented preferentially in a direction perpendicular to the film plane. This conclusion is consistent with the usual observation that aggregate absorption in MEH-PPV films is not easily observed using absorption spectra alone, which are typically measured at normal incidence. [ABSTRACT FROM AUTHOR]

Semiconducting polymers inherently exhibit polydispersity in terms of molecular structure and microscopic morphology, which often results in a broad distribution of energy levels for localized electronic states. Therefore, the bulk charge mobility strongly depends on the free charge density. In this study, we propose a method to measure the charge-density-dependent bulk mobility of conjugated polymer films with widely spread localized states using a conventional field-effect transistor configuration. The gate-induced variation of bulk charge density typically ranges within ±1018 cm−3; however, this range depends significantly on the energetic dispersion width of localized states. The field-effect bulk mobility and field-effect mobility near the semiconductor–dielectric interface along with their dependence on charge density can be simultaneously extracted from the transistor characteristics using various gate voltage ranges. [ABSTRACT FROM AUTHOR]

To impart high stretchability to semiconducting polymers, researchers have used a photocrosslinking approach based on the nitrene chemistry of an azide‐incorporated molecular additive. However, understanding of the molecular design of azide crosslinkers with respect to their effects on the electrical and mechanical properties of semiconducting polymer thin films is lacking. In this study, the effects of an azide photocrosslinker's molecular length and structure on the microstructural, electrical features, and stretchability of photocrosslinked conjugated polymer films is investigated. For a systematic comparison, a series of nitrene‐induced photocrosslinkers (n‐NIPSs) with different numbers of ethylene glycol repeating units (n = 1, 4, 8, 13) that bridge two tetrafluoro‐aryl azide end groups is synthesized. Two semicrystalline conjugated polymers and two nearly amorphous conjugated polymers are co‐processed with n‐NIPSs and crosslinked by brief exposure to UV light. It is found that, among the synthesized n‐NIPSs, the shortest one (1‐NIPS) is the most efficient in improving the stretchability of crosslinked indacenodithiophene‐benzothiadiazole films and that the improvement is achieved only with nearly amorphous polymers, not with semicrystalline conjugated polymers. On the basis of systematic studies, it is suggested that crosslinking density in amorphous regions is important in improving thin film stretchability. [ABSTRACT FROM AUTHOR]

In this study, we developed two novel conjugated polymers that can easily be doped with F4TCNQ organic dopants using a sequential doping method and then studied their organic thermoelectric (OTE) properties. In particular, to promote the intermolecular ordering of OTE polymers in the presence of the F4TCNQ dopant, alkylthiazole-based conjugated building blocks with highly planar backbone structures were synthesized and copolymerized. All polymers showed strong molecular ordering and edge-on orientation in the film state, even in the presence of the F4TCNQ organic dopant. Thus, the sequential doping process barely changed the molecular ordering of the polymer films while making efficient molecular doping. In addition, the doping efficiency was improved in the more π-extended polymer backbones with thienothiophene units due to the emptier space in the polymer lamellar structure to locate ionized F4TCNQ. Moreover, the study of organic thin-film transistors (OTFTs) revealed that higher hole mobility in OTFTs was the key to increasing the electrical conductivity of OTE devices fabricated using the sequential doping method. [ABSTRACT FROM AUTHOR]

Featured Application: Authors are encouraged to provide a concise description of the specific application or a potential application of the work. This section is not mandatory. Electrically conductive polymer materials are increasingly being used as electronic materials, for example, in thin-film transistors. However, the low mobility of charge carriers limits their use. One of the ways to increase the mobility of charge carriers can be the use of interface conductivity along the regions separating the two polymer films. It is important that it could be realized with non-conjugated polymers. There is no direct experimental evidence that the transport of charge carriers occurs along such an interface. It is impossible to deny the possibility of transport on the surfaces of polymer films. The purpose of this work is to study the current flow path in a multilayer sample by marking the polymer–polymer interface with a doping nanolayer of a Cu2O island film. Spectral methods in the field of electronic absorption of copper oxide were used to control the island film. The electronic parameters of the polymer–polymer interface were studied using injection methods and volt-ampere characteristics. Atomic force microscopy was used to control the thickness and uniformity of the samples. It was found that the doping of the polymer–polymer interface using Cu2O particles strongly affects the transport of charge carriers; in particular, the conductivity of the structure increases. It is established that this is due to an increase in the mobility of the charge carriers and a decrease in the height of the potential barrier at the 3D metal–2D interface area. Thus, it is established that the transport of charge carriers occurs along the polymer–polymer interface at the structure parameters specified in this work. [ABSTRACT FROM AUTHOR]

HCl doped-copolymer of ortho phenylene diamine, meta phenylene diamine, and pyrrole terpolymers blend was synthesized. Physical vapor deposition was used to produce the terpolymer-blended thin films, allowing the creation of the fiber structure at a low deposition rate, with a chamber pressure of 5 × 10−5 mbar and a thickness of 100 ± 2 nm. The produced thin films of terpolymers blend were examined utilizing a combination of theoretical and experimental techniques including TD-DFT/DMol3, CATSTEP, FT-IR spectrum, XRD, and optical characterizations. According to XRD computations, the terpolymers blend had an average crystallite size of 190 ± 2 nm, while SEM measurements showed that the length of the fibers was ≅ 73 ± 2 μm. The blend of terpolymers displayed an absorbance of 1.83 at 612 nm. Additionally, the blend of terpolymers' indirect/direct bandgap and absorption index was observed with noticeable alterations. The molecular structure optimization and frequency calculations for the crystal models and isolated molecules were carried out using the materials studio 7.0 tool (TDDFT/DMol3 and CASTEP). The DFT-Gaussian09W-vibration values closely matched the experimental results in terms of structure and optical characteristics. The application of thin films in polymer solar cell applications looks promising due to the noticeable improvements in optical characteristics. [ABSTRACT FROM AUTHOR]

For the first time, the simultaneous synthesis and deposition of heterometallic porphyrin conjugated polymer thin films from a simple and scalable gas‐phase approach are reported. The oxidative chemical vapor deposition (oCVD) reaction of 5,15‐(diaryl) porphyrins chelated with different metal cations (M = Co(II), Ni(II), Zn(II), Cu(II), Pd(II)) readily yields the formation of new hetero‐metalated fused porphyrin tapes, such as evidenced by in‐depth high‐resolution mass spectrometry studies. The impact of the coreactants on the regioselectivity of the intermolecular dehydrogenative coupling reaction and the formation of double or triple bonds between the porphyrin units is demonstrated. The oCVD reaction of multiple porphyrins brings the possibility to easily engineer the chemical features and the electronic and optoelectronic properties of these highly conjugated porphyrin polymers. Particularly, it is demonstrated that porphyrin conjugated polymers having different chelated metal cations can achieve higher electrical conductivities and promote narrower bandgaps. The gas‐phase approach presented herein overcomes the main limitations of the conventional solution‐based approaches and opens the path to the engineering of a novel class donor–acceptor heterometallic polymers with high interest in several fields including multimetallic electrocatalysis, photocatalysis, sensing, and nonlinear optics applications. [ABSTRACT FROM AUTHOR]

It is shown in this paper that a polymer, MA-PEG 1000-DGEBA (MP1D), exhibits antireflection, substrate-dependent photoluminescence (SDP), wide band-gap, and photoconduction characterization. MP1D was synthesized from maleic anhydride, polyethylene glycol 1000, and bisphenol-A diglycidyl ether. Self-assembled nanoparticles embedded in MP1D film and ranging from 2.5 to 31.6 nm are observed, which could be expected as scatterers to enhance light trapping and extraction. The size of the nanoparticle increases with the concentration of the MP1D solution. Besides solution concentration, the nanoparticle dimension could be modified by the chain length of polyethylene glycol in the polymer synthesis. The effects of solution concentration, annealing temperature, annealing period, and substrate on the photoluminescence (PL) of MP1D films are examined. Increasing solution concentration increases PL intensity. However, aggregation-caused quenching is explicit as the solution concentration exceeds 100 mM. PL intensity increases with annealing temperature, which could be attributed to crystallinity improvement. PL intensity increases with increasing the annealing period from 0.5 to 2 h. Nonetheless, as the annealing period exceeds 2 h, PL quenching is emerging, which could be due to aggregation. It is expected that MP1D could be a promising candidate for host materials and MP1D film could play a multifunctional role (antireflective and light-trapping functions) in optoelectronics. [ABSTRACT FROM AUTHOR]

Four novel isoindigo–thiophene D–A–D–type precursors are synthesized by Stille coupling and electrosynthesized to yield corresponding hybrid polymers with favorable electrochemical and electrochromic performances. Intrinsic structure–property relationships of precursors and corresponding polymers, including surface morphology, band gaps, electrochemical properties, and electrochromic behaviors, are systematically investigated. The resultant isoindigo–thiophene D–A–D–type polymer combines the merits of isoindigo and polythiophene, including the excellent stability of isoindigo–based polymers and the extraordinary electrochromic stability of polythiophene. The low onset oxidation potential of precursors ranges from 1.10 to 1.15 V vs. Ag/AgCl, contributing to the electrodeposition of high–quality polymer films. Further kinetic studies illustrate that isoindigo–thiophene D–A–D–type polymers possess favorable electrochromic performances, including high optical contrast (53%, 1000 nm), fast switching time (0.8 s), and high coloration efficiency (124 cm2 C−1). These features of isoindigo–thiophene D–A–D–type conjugated polymers could provide a possibility for rational design and application as electrochromic materials. [ABSTRACT FROM AUTHOR]

A polydiphenylacetylene derivative containing a trimethylsilyl group in one of the two side phenyl rings (PDPA-C1) was examined for use in a film-type solid-state sensor to determine the viscosity of various fluids, such as alcohols, fatty oils, and mineral oils. The fluids readily diffused into the polymer film upon contact and, simultaneously, the fluorescence (FL) emission increased with time to reach a FL enhancing equilibrium. The FL enhancing rate decreased as the viscosity of the fluids increased. The relationship between the time to reach the FL enhancing equilibrium (teq, FL) and the viscosity of each fluid (η) was captured well by a modified Forster–Hoffmann equation, log teq, FL = C + x log η. The slope (x) values indicate the viscosity sensitivities of the PDPA-C1 film for the fluids, which were determined to be 1.02 for alcohols, 4.15 for fatty oils, and 0.63 for mineral oils. This sensing process yielded not only significantly higher viscosity sensitivities but also higher reproducibility than the conventional sensing process based on the measurement of FL intensity. The typical Forster–Hoffmann equation did not capture the relationship between the probe FL intensity and the fluid viscosity well. The unknown viscosities of commercial oils were identified exactly using the modified Forster–Hoffmann equation as a calibration curve. [ABSTRACT FROM AUTHOR]

Organic field-effect transistor (OFET) gas sensors based on conjugated polymer films have recently attracted considerable attention for use in environmental monitoring applications. However, the existing devices are limited by their poor sensing performance for gas analytes. This drawback is attributed to the low charge transport in and the limited charge–analyte interaction of the conjugated polymers. Herein, we demonstrate that the incorporation of graphitic carbon nitride (g-C₃N₄) into the conjugated polymer matrix can improve the sensing performance of OFET gas sensors. Moreover, the effect of graphitic carbon nitride (g-C₃N₄) on the gas sensing properties of OFET sensors based on poly(3-hexylthiophene) (P3HT), a conjugated polymer, was systematically investigated by changing the concentration of the g-C₃N₄ in the P3HT/g-C₃N₄ composite films. The obtained films were applied in OFET to detect NO gas at room temperature. In terms of the results, first, the P3HT/g-C₃N₄ composite films containing 10 wt.% g-C₃N₄ exhibited a maximum charge carrier mobility of ~1.1 × 10−1 cm2 V−1 S−1, which was approximately five times higher than that of pristine P3HT films. The fabricated P3HT/g-C₃N₄ composite film based OFET sensors presented significantly enhanced NO gas sensing characteristics compared to those of the bare P3HT sensor. In particular, the sensors based on the P3HT/g-C₃N₄ (90/10) composite films exhibited the best sensing performance relative to that of the bare P3HT sensor when exposed to 10 ppm NO gas: responsivity = 40.6 vs. 18.1%, response time = 129 vs. 142 s, and recovery time = 148 vs. 162 s. These results demonstrate the enormous promise of g-C₃N₄ as a gas sensing material that can be hybridized with conjugated polymers to efficiently detect gas analytes. [ABSTRACT FROM AUTHOR]

The solid‐state molecular orientation of conjugated polymers is of vital importance for their charge transport properties, where the edge‐on orientation with π‐stacking direction parallel to the surface is generally preferable to achieving high‐mobility planar field‐effect transistors. However, so far, little is known about the origin of packing‐orientation formation in thin films. Here, it is shown that the solution‐state supramolecular structure of widely studied PffBT4T‐based polymers can be reversibly tuned between 1D worm‐like and 2D lamellar structures for the same polymer/solvent system through solution temperature. Such dimensionality in solution determines the solid‐state packing orientation of the polymer chains, where edge‐on and face‐on textures are generated from solutions with 1D and 2D structures, respectively. More importantly, the transition temperature of solution‐state supramolecular dimensionality is in excellent agreement with that of solid‐state packing orientation. These experimental observations unambiguously demonstrate the predominant roles of solution‐state supramolecular assembly in solid‐state molecular orientation, which is further verified using different molecular weight batches and other two representative polymers. The findings provide new insights into the growth mechanism of polymer semiconductors during transistor fabrication, and open prospective pathways for boosting device performance of solution‐processable plastic electronics. [ABSTRACT FROM AUTHOR]

Efficient doping of polymer semiconductors is required for high conductivity and efficient thermoelectric performance. Lewis acids, e.g., B(C6F5)3, have been widely employed as dopants, but the mechanism is not fully understood. 1:1 "Wheland type" or zwitterionic complexes of B(C6F5)3 are created with small conjugated molecules 3,6‐bis(5‐(7‐(5‐methylthiophen‐2‐yl)‐2,3‐dihydrothieno[3,4‐b][1,4]dioxin‐5‐yl)thiophen‐2‐yl)‐2,5‐dioctyl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione [oligo_DPP(EDOT)2] and 3,6‐bis(5''‐methyl‐[2,2':5',2''‐terthiophen]‐5‐yl)‐2,5‐dioctyl‐2,5‐dihydropyrrolo[3,4‐c]pyrrole‐1,4‐dione [oligo_DPP(Th)2]. Using a wide variety of experimental and computational approaches, the doping ability of these Wheland Complexes with B(C6F5)3 are characterized for five novel diketopyrrolopyrrole‐ethylenedioxythiophene (DPP‐EDOT)‐based conjugated polymers. The electrical properties are a strong function of the specific conjugated molecule constituting the adduct, rather than acidic protons generated via hydrolysis of B(C6F5)3, serving as the oxidant. It is highly probable that certain repeat units/segments form adduct structures in p‐type conjugated polymers which act as intermediates for conjugated polymer doping. Electronic and optical properties are consistent with the increase in hole‐donating ability of polymers with their cumulative donor strengths. The doped film of polymer (DPP(EDOT)2‐(EDOT)2) exhibits exceptionally good thermal and air‐storage stability. The highest conductivities, ≈300 and ≈200 S cm−1, are achieved for DPP(EDOT)2‐(EDOT)2 doped with B(C6F5)3 and its Wheland complexes. [ABSTRACT FROM AUTHOR]

The sensing properties of poly 3‐(3‐carboxypropyl) thiophene‐2,5‐diyl (PT‐COOH) and hydroxylated polythiophene (PT‐OH) as bioreceptor layers were studied and are discussed in this paper. The polymer films cover the channel region of the OECT devices and anti‐human IgG was immobilized on the polymer films. We use threshold voltage (Vth) change as a sensing signal to detect the interaction between anti‐human IgG and human IgG. By adding different concentrations of human IgG, Vth difference can be observed on anti‐human IgG immobilized polymer films, with optimized detection from a blend of the two polymers. Open circuit potential (OCP) measurement was also done on the OECT devices based on the same anti‐human IgG and human IgG interaction pair to help us understand the mechanism behind the antibody functionalization and the interaction between antibody and antigen. Importantly, the observed positive OCP change for the PT‐OH system was self‐consistent with the negative OECT Vth change that was obtained, since the latter is applied to the gate while the former is measured at the channel. [ABSTRACT FROM AUTHOR]

Four new multifunctional polymers (P1, P2, P3, and P4) containing EDOT units were synthesized by the Stille coupling reaction. A PL spectrum test found that the introduction of large conjugated groups led to strong fluorescence emission in all polymers. Among the electrochromic and switch properties, these polymer films exhibited reversible color changes, as well as good coloring efficiency. Electrochemical experiments found that the initial oxidation potentials of the polymers were 1.27 V, 1.67 V, 1.78 V, and 1.58 V, respectively. Among them, P3 showed a higher coloring efficiency (283.3 cm2·C−1), and P2 showed a shorter response time (tc = 2.2 s, tb = 2.8 s). These polymers all exhibited electrochromic and resistive switching storage characteristics. They have good solubility in many organic solvents. In the resistance switch memory characteristics, all polymers had obvious memristive properties, and P4 exhibited a larger switch current ratio (2527.42) and a smaller threshold voltage (0.9 V). [ABSTRACT FROM AUTHOR]

[Display omitted] • Chemical dissolution of D-A conjugated network polymers in liquid amines. • A universal approach to processing conjugated polymers on various substrates. • High stability and enhanced photoactivity of fabricated thin films. • Large-area thin films exhibited good photocatalytic H 2 O 2 production in pure water. Conjugated network polymers (CNPs) have gained considerable attention as heterogeneous photocatalysts, however, their limited solubility in solvents poses a significant challenge in employing CNPs for photoreactors. Herein, we report the chemical dissolution of CNPs in aminic solvents to enhance solution processability. The CNPs, synthesized via the Knoevenagel polycondensation, were dissolved into corresponding polymer inks, forming thin films on various substrates through mild heating. Residual functional groups on the CNP surface provided latent reactive sites for liquid amines, facilitating structural disentanglement and dissolution without hindering the π-conjugation. The resulting polymer films on FTO electrodes exhibited broader light absorbance and > 2-fold enhanced photoresponse compared to CNP powder films. Photocatalytic production of H 2 O 2 using the large-area polymer film (254.4 cm2) demonstrated sustained activity with a production rate of 0.21 mM H 2 O 2 h−1 over 14 h without sacrificial agents. These findings lay the groundwork for applying CNP photocatalysts in chemical, optical, and electronic applications. [ABSTRACT FROM AUTHOR]

Reversibility and durability have become new bottlenecks for conjugated polymers to realize "stretchable" semiconducting devices. Therefore, the correlation between microstructure and mechanical properties requires explicit delineation. Herein, the deformation and fracture mechanisms of DPP-TVT (poly [2,5-bis(4-decyl tetradecyl) pyrrolo [3,4-c]pyrrole-1,4-(2H, 5H)-dione-(E)-1,2-di (2,2′-bithiophen-5-yl)ethene) films with various degree of lamellar order were investigated from microscopic view. In the medium ordered films, the lamellae and amorphous phase cooperate to form the fibrous network structure in respond to tensile deformation. When recovered, this fibrous network could deform and being compressed, providing an efficient stress transfer pathway to accommodate the residual strain. Therefore, the medium ordered films did not form cracks even under 100 cycles of 50 % strain. However, in near-amorphous films, the uniformly aligned chains in stretched films were difficult to reorient under compression, resulting in the formation of large wrinkles and poor fatigue resistance. And the highly ordered films generate cracks both under single and cyclic stretch due to lacking of stress dissipation pathways. This study lays the groundwork for enhancing the mechanical robustness of conjugated polymer films. [Display omitted] • Displayed the microstructure change during stretch in conjugated polymer film. • Investigated the relation between morphology and deformation mechanism. • Proposed that medium degree of order is favorable for fatigue behavior. [ABSTRACT FROM AUTHOR]

Bredereck oxazole synthesis was utilized to create a series of novel D-A polymers based on the triphenylamine (TPA) derivative, 4,4′-Diformyltriphenylamine (DPA), 4,4′-((4-bromophenyl)azanediyl)dibenzaldehyde (BPA), and oxamide/dithiooxamide. The obtained novel polymers exhibited impressive solution processabilities and excellent thermal stabilities. In the entire processes of electrochemical oxidation, these polymer films exhibited excellent electrochromic (EC) performances, high optical contrasts (49.6–52.8 %), high coloration efficiencies (362–451 cm2·C−1), and excellent cycling stabilities (18.6–33.9 % decay) with a cycle time of 20 s. By applying voltage, electrofluorochromic (EFC) performance can also be adjusted. Furthermore, these polymers showed fluorescence (PL) in solvents and solvatochromic effects in absorption. The outcome was indicative of the addition of oxazole[5,4- d ]oxazoles (OzOz) and thiazolo[5,4- d ]thiazoles (TzTz), whose highly conjugate rigid planar structures can significantly increase molecule stabilities and minimizing volume shrinking during charge transfer. In addition, due to introducing bromine atoms, the p-π conjugations enhanced the conjugation degrees of the molecules, which facilitated the electron transfers. Experimental results show that these improvement schemes will pave a way for obtaining multi-function optoelectronic devices with long-term cyclic stabilities. [Display omitted] • The electrochromic stability was optimized by introducing TzTz-type/OzOz-type group to the polymers. • Polymers were synthesized using fewer steps and cheap raw materials. • The introduction of fluorescent chromophore the fluorescence properties of the polymer and increased their potential purposes. [ABSTRACT FROM AUTHOR]

To investigate the effect of double fluorine substitution on the optical, electrochemical, thermodynamic, morphological and electrochromic properties of electrochromic polymers, two benzotriazole-EDOT electrochromic conjugated polymers PBTz-E and P2F-BTz-E were synthesized via direct (hetero)arylation polymerization (DHAP). P2F-BTz-E was obtained after fluorination of PBTz-E by substituting two hydrogen atoms on the benzotriazole unit with two fluorine atoms. Both polymers exhibited similar purple colors in the neutral state, and the polymer films reversibly and stably switched between neutral and oxidized states with minimal degradation over 1000 s. The optical contrast, response time and electrochemical stability of P2F-BTz-E are significantly improved, and the reduction time can reach sub-second speed (0.5 s). However, the severe stacking and aggregation of fluorinated polymer P2F-BTz-E resulted in unsatisfactory film surface morphology and low coloration efficiency. Surprisingly, PBTz-E shows magnificent coloration efficiency (774 cm2 C−1 at 570 nm) because of the low transfer charge. Flexible ECDs prepared from two polymers demonstrated good reversible electrochromic properties. These results provide valuable information for the elaboration of high-performance electrochromic polymers based on benzotriazole. [ABSTRACT FROM AUTHOR]

The molecular weight is a key factor affecting the properties of conjugated polymers. To determine the critical molecular weights of conjugated polymers modified with siloxane side chains, poly‐diketo‐pyrrolopyrrole‐selenophene (PTDPPSe‐5Si) samples with molecular weights ranging from 20 to 350 kDa are synthesized. The critical molecular weight of the polymer is determined in the range of 60–100 kDa by testing the viscosity of the solution. When the molecular weight of the 27–60 kDa polymers is below the critical molecular weight, they exhibit a high crystallinity and low ductility. When the molecular weight of the 100 kDa polymer reaches the critical molecular weight, the crystallinity decreases, and the ductility increases. As the molecular weight increases, the polymer film also gradually changes from brittle to ductile. Furthermore, when the molecular weight of the 315 kDa polymer is much higher than the critical molecular weight, the film exhibits a significant ductility, which results in the polymer films showing no pronounced cracks after high‐percentage stretching. Additionally, due to the oriented alignment of the molecular chains caused by stretching, the carrier mobility in the parallel direction becomes 2.14‐fold of the initial film. [ABSTRACT FROM AUTHOR]

Nerve agents, one of the most toxic chemical warfare agents, seriously threaten human life and public security. The high toxicity of nerve agents makes the development of fluorescence sensors with suitable limit of detection challenging. Here, we propose a sensor design based on a conjugated microporous polymer film for the detection of diethyl chlorophosphate, a substitute of Sarin, with low detection limit of 2.5 ppt. This is due to the synergy of the susceptible on-off effect of hybridization and de-hybridization of hybrid local and charge transfer (HLCT) materials and the microporous structure of CMP films facilitating the inward diffusion of DCP vapors, and the extended π-conjugated structure. This strategy provides a new idea for the future development of gas sensors. In addition, a portable sensor is successfully integrated based on TCzP-CMP films that enables wireless, remote, ultrasensitive, and real-time detection of DCP vapors. The high toxicity of nerve agents makes the development of fluorescence sensors with suitable limit of detection challenging. Here, the authors propose a sensor design based on a conjugated microporous polymer film for the detection of diethyl chlorophosphate, a substitute of Sarin, with low detection limit of 2.5 ppt. [ABSTRACT FROM AUTHOR]

The charge carrier transport of conjugated polymer thin film is mainly decided by the crystalline domain and intercrystallite connection. High‐density tie‐chain can provide an effective bridge between crystalline domains. Herein, the tie‐chain connection behavior is optimized by decreasing the crystal region length (lc) and increasing the crystallization rate. Poly[4‐(4,4‐bis(2‐octyldodecyl)‐4H‐cyclopenta[1,2‐b:5,4‐b′]dithiophen‐2‐yl)‐alt‐[1,2,5]‐thiadiazolo[3,4‐c]pyridine] (PCDTPT‐ODD) is dissolved in nonpolar solvent isooctane and high ordered rod‐like aggregations are formed. As the temperature increases, the changes in solution state and crystallization behavior lead to three different chain arrangement morphologies in the films: 1) at 25 °C, large and separated crystal regions are formed; 2) at 55 °C, small and well‐connected crystal regions are formed due to faster crystallization rate and smaller nucleus size; 3) at 90 °C, the amorphous film is formed. Further results show that the film prepared at 55 °C has a smaller crystal region length (lc, 7.6 nm) and higher tie‐chains content. Thus, the film exhibits the best device mobility of 2.3 × 10−3 cm2 V−1 s−1. This result shows the great influence of crystallization kinetics on the microstructure of conjugated polymer films and provides an effective way for the optimization of the intercrystallite tie‐chain. [ABSTRACT FROM AUTHOR]

Polymer semiconductor/gate dielectric interface is well known to influence the charge transport behaviors in organic field-effect transistors (OFETs). In the unidirectional floating-film transfer method (UFTM), thin floating films of uniaxially aligned π-conjugated polymers are solidified at the air/liquid interface before transferring them onto device substrates. Therefore, packing structures in the films prepared by UFTM are not affected by the strong interactions with the device substrate as usually seen in other film growth methods. Here, one question arises: will the difference in interactions between the liquid substrate and air impact the orientational structure of the polymer chain near the two surfaces or not? To answer this question, we have studied the charge-transport anisotropy in top- and bottom-gate OFETs by changing the film thickness. As a result, the field-effect carrier mobility and its anisotropy did not significantly differ for both surfaces and were constant against the film thickness. These results indicate that the UFTM can provide unidirectional alignment of polymer chains throughout the film thickness and gives a similar superior performance either for a bottom- or a top-gate OFET. [ABSTRACT FROM AUTHOR]

Conjugated polymers (CPs) are promising semiconductors for intrinsically stretchable electronic devices. Ideally, such CPs should exhibit high charge mobility, excellent stability, and high stretchability. However, converging all these desirable properties in CPs has not been achieved via molecular design and/or device engineering. This work details the design, synthesis and characterization of a random polythiophene (RP-T50) containing ~50 mol% of thiophene units with a thermocleavable tertiary ester side chain and ~50 mol% of unsubstituted thiophene units, which, upon thermocleavage of alkyl chains, shows significant improvement of charge mobility and stability. Thermal annealing a RP-T50 film coated on a stretchable polydimethylsiloxane substrate spontaneously generates wrinkling in the polymer film, which effectively enhances the stretchability of the polymer film. The wrinkled RP-T50-based stretchable sensors can effectively detect humidity, ethanol, temperature and light even under 50% uniaxial and 30% biaxial strains. Our discoveries offer new design rationale of strategically applying CPs to intrinsically stretchable electronic systems. Conjugated polymers are promising semiconductors for stretchable electronic devices but combining important properties such as high charge mobility, stability and stretchability remains challenging. Here, the authors demonstrate the synthesis of a thiophene based semiconducting polymer with cleavable side chains which shows significant improvement of charge mobility, stability and stretchability. [ABSTRACT FROM AUTHOR]

Protective layers formed of polymers with conjugated structures have been demonstrated to improve the cycling stability of lithium (Li)‐metal batteries by reducing Li dendrite growth. However, the influence of important film parameters, such as thickness and ionic conductivity, remains largely unexplored. The present work addresses this issue by investigating the influence of film thickness for electrochemically active polymethyl methacrylate (PMMA) protective layers on the growth of Li dendrites and the long‐term cycling stability of Li‐metal batteries. The results demonstrate that the cycling stability of cells employing PMMA/Cu electrodes attains a maximum value at an optimal polymer film thickness of 93 nm. The results of detailed analysis indicate that the optimal PMMA layer thickness improves the cycling stability of Li‐metal batteries by eliminating the uneven electric fields on the surface of the Cu electrode leading to Li dendrite growth, and by reducing the interfacial impedance due to the formation of intramolecular cyclopentanedione during the discharge/charge cycling. Accordingly, the results provide effective guidance in the future design of polymer protective layers by demonstrating that film thickness is a key factor influencing the cycling stability of Li‐metal batteries. [ABSTRACT FROM AUTHOR]

Molecular doping of conjugated polymers causes bleaching of the neutral absorbance and results in new polaron absorbance transitions in the mid and near infrared. Here, the concentration dependent changes in the spectra for a series of molecularly doped diketopyrrolopyrrole (DPP) co‐polymers with a series of ultra‐high electron affinity cyanotrimethylenecyclopropane‐based dopants is analyzed. With these strong dopants the polaron mole fraction (Θ) reaches saturation. Analysis of the full spectrum enables separation of neutral and polaron signals and quantification of the polaron mole fraction using a simple noninteracting site model. The peak ratios for both neutral and polaron peaks change systematically with increasing polaron mole fraction for all measured polymers. Analysis of the spectral changes indicates that the polaron mole fraction can be quantified to within 5%. While the total change in the absorbance spectrum with increasing polaron mole fraction is linear, the lowest energy polaron peak (P1) grows nonlinearly, which indicates increased polarization/delocalization. Molecular doping of polymers that form either H‐ or J‐aggregates shows systematically different spectral changes in the vibronic peak ratios of the neutral spectra and provides insights into the polymer configuration at undoped sites in the film. [ABSTRACT FROM AUTHOR]

[Display omitted] • Ordered solid-state semicrystalline domains were formed by tuning solution-state polymer aggregations. • Power factors were enhanced about at least 15-fold by heated evaporating process. • PBDT-F15 achieved the highest power factor among the reported benzodithiophene-based conjugated polymers. Controlling solution-state aggregation of conjugated polymers is crucial for tuning solid-state morphology as well as electrical properties. However, the effect of solution-state aggregation on their thermoelectric performance is rarely reported. Using a series of poly(benzodithiophene- alt -thiophene) conjugated polymers (PBDT-Fm, m is the content of semi-fluorinated groups in polymer chain), the polymer solution aggregations were tuned by the evaporation temperature, which has achieved optimized P(BDT-Fm) films with high degree of molecular order, homogeneous polymer aggregates and small crystalline domains, leading to dramatic enhancement in thermoelectric performance. Compared with the naturally dried polymer films, the heated evaporating process led to at least 49-fold and 15-fold enhancement in the conductivity and power factor, respectively. Optical spectroscopy and microcosmic morphology have shown that the strong molecular motion of polymer chains at high evaporation temperature would disaggregate the polymer pre-aggregations in solution and assist the formation of orderly packed microstructures in solid state, leading to a significant increase in the power factor. Through controlling solution-state polymer aggregations, PBDT-F15 achieved the power factors up to 7.74 ± 0.01 µW m−1 K−2, which is among the highest values in the reported benzodithiophene-based conjugated polymers, highlighting the importance of controlling polymer solution aggregation in optimizing thermoelectric performance. [ABSTRACT FROM AUTHOR]