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Although most polymer/fullerene-based solar cells are cast from a blend of the components in solution, it is also possible to sequentially process the polymer and fullerene layers from quasi-orthogonal solvents. Sequential processing (SqP) not only produces photovoltaic devices with efficiencies comparable to the more traditional bulk heterojunction (BHJ) solar cells produced by blend casting (BC) but also offers the advantage that the polymer and fullerene layers can be optimized separately. In this paper, we explore the morphology produced when sequentially processing polymer/fullerene solar cells and compare it to the BC morphology. We find that increasing polymer regioregularity leads to the opposite effect in SqP and BC BHJ solar cells. We start by constructing a series of SqP and BC solar cells using different types of poly(3-hexylthiophene) (P3HT) that vary in regioregulary and polydispersity combined with [6,6]-phenyl-C61-butyric-acid-methyl-ester (PCBM). We use grazing incidence wide-angle X-ray scattering to demonstrate how strongly changes in the P3HT and PCBM crystallinity upon thermal annealing of SqP and BC BHJ films depend on polymer regioregularity. For SqP devices, low regioregularity P3HT films that possess more amorphous regions allow for more PCBM crystallite growth and thus show better photovoltaic device efficiency. On the other hand, highly regioregular P3HT leads to a more favorable morphology and better device efficiency for BC BHJ films. Comparing the photovoltaic performance and structural characterization indicates that the mechanisms controlling morphology in the active layers are fundamentally different for BHJs formed via SqP and BC. Most importantly, we find that nanoscale morphology in both SqP and BC BHJs can be systematically controlled by tuning the amorphous fraction of polymer in the active layer. © 2014 American Chemical Society.

The results of a combined grazing incidence wide-angle X-ray scattering (GIWAXS) and 4D scanning transmission microscopy (4D-STEM) analysis of the effects of thermal processing on poly(3[2-(2-methoxyethoxy)ethoxy]-methylthiophene-2,5-diyl) are reported, a conjugated semiconducting polymer used as the active layer in organic electrochemical transistor devices. GIWAXS provides a measure of overall crystallinity in the film, while 4D-STEM produces real-space maps of the morphology and orientation of individual crystallites along with their spatial extent and distribution. The sensitivity of the 4D-STEM detector allows for collection of electron diffraction patterns at each position in an image scan while limiting the imparted electron dose to below the damage threshold. The effects of heat treatment on the distribution and type of crystallites present in the films is determined., (© 2024 Wiley‐VCH GmbH.)

In this work, an efficient and robust hole transport layer (HTL) based on blended poly((9,9-dioctylfluorenyl-2,7-diyl)- alt -(9-(2-ethylhexyl)-carbazole-3,6-diyl)) (PF8Cz) and crosslinkable 3,3'-(9,9-dimethyl-9 H -fluorene-2,7-diyl)bis(9-(4-vinylphenyl)-9 H -carbazole) (FLCZ-V) is introduced for high-performance and stable blue quantum dot-based light-emitting diodes (QLEDs), wherein FLCZ-V can in situ-crosslink to a continuous network polymer after thermal treatment and the linear polymer PF8CZ becomes intertwined and imprisoned. As a result, the blended HTL shows a high hole mobility (1.27 × 10 -4 cm 2 V -1 s -1 ) and gradient HOMO levels (-5.4 eV of PF8CZ and -5.7 eV of FLCZ-V) that can facilitate hole injecting so as to ameliorate the charge balance and, at the same time, achieve better electron-blocking capability that can effectively attenuate HTL decomposition. Meanwhile, the crosslinked blended HTL showed excellent solvent resistance and a high surface energy of 40.34 mN/m, which is favorable to enhance wettability for the deposition of a follow-up layer and attain better interfacial contact. Based on the blended HTL, blue QLEDs were fabricated by both spin-coating and inkjet printing. For the spin-coated blue QLED, a remarkable enhancement of external quantum efficiency (EQE) of 15.5% was achieved. Also, the EQE of the inkjet-printed blue QLED reached 9.2%, which is thus far the best result for the inkjet-printed blue QLED.

Considering the increasing demand for high-resolution light-emitting diodes (LEDs), it is important that direct fine patterning technologies for LEDs be developed, especially for quantum-dot LEDs (QLEDs). Traditionally, the patterning of QLEDs relies on resin-based photolithography techniques, requiring multiple steps and causing performance deterioration. Nondestructive direct patterning may provide an easy and stepwise method to achieve fine-pixelated units in QLEDs. In this study, two isomeric tridentate cross-linkers (X8/X9) are presented and can be blended into the hole transport layer (HTL) and the emissive layer (EML) of QLEDs. Because of their photosensitivity, the in situ cross-linking process can be efficiently triggered by ultraviolet irradiation, affording high solvent resistance and nondestructive direct patterning of the layers. Red QLEDs using the cross-linked HTL demonstrate an impressive external quantum efficiency of up to 22.45%. Through lithographic patterning enabled by X9, line patterns of HTL and EML films exhibit widths as narrow as 2 and 4 μm, respectively. Leveraging the patterned HTL and EML, we show the successful fabrication of pixelated QLED devices with an area size of 3 × 3 mm 2 , alongside the successful production of dual-color pixelated QLED devices. These findings showcase the promising potential of direct patterning facilitated by engineered cross-linkers for the cost-effective fabrication of pixelated QLED displays.

Polythiophenes are one of the most widely studied conjugated polymers. With the discovery of the chain mechanism of Kumada catalyst-transfer polymerisation (KCTP), various polythiophene copolymer structures, such as random, block, and gradient copolymers, have been synthesized via batch or semi-batch (sequential addition) methods. However, the lack of quantitative kinetic data for thiophene monomers brings challenges to experimental design and structure prediction when synthesizing the copolymers. In this study, the reactivity ratios and the polymerisation rate constants of 3-hexylthiophene with 4 thiophene comonomers in KCTP are measured by adapting the Mayo-Lewis equation and the first-order kinetic behaviour of chain polymerisation. The obtained kinetic information highlights the impact of the monomer structure on the reactivity in the copolymerisations. The kinetic data are used to predict the copolymer structure of equimolar batch copolymerisations of the 4 thiophene derivatives with 3-hexylthiophene, with the experimental data agreeing well with the predictions. 3-Dodecylthiophene and 3-(6-bromo)hexylthiophene, which have higher structural similarity to 3-hexylthiophene, show nearly equivalent reactivity to 3-hexylthiophene and give random copolymers in the batch copolymerisation. 3-(2-Ethylhexyl)thiophene with a branched side chain is less reactive compared to 3-hexylthiophene and failed to homopolymerize at room temperature, but produced gradient copolymers with 3-hexylthiophene. Finally, the bulkiest 3-(4-octylphenyl)thiophene, despite its ability to homopolymerize, failed to maintain chain polymerisation in the copolymerisation with 3-hexylthiophene, possibly due to the large steric hindrance caused by the phenyl ring directly attached to the thiophene center. This study highlights the importance of monomer structures in copolymerisations and the need for accurate kinetic data., Competing Interests: The authors have no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

Understanding the factors underpinning device switching times is crucial for the implementation of organic electrochemical transistors in neuromorphic computing, bioelectronics and real-time sensing applications. Existing models of device operation cannot explain the experimental observations that turn-off times are generally much faster than turn-on times in accumulation mode organic electrochemical transistors. Here, using operando optical microscopy, we image the local doping level of the transistor channel and show that turn-on occurs in two stages-propagation of a doping front, followed by uniform doping-while turn-off occurs in one stage. We attribute the faster turn-off to a combination of engineering as well as physical and chemical factors including channel geometry, differences in doping and dedoping kinetics and the phenomena of carrier-density-dependent mobility. We show that ion transport limits the operation speed in our devices. Our study provides insights into the kinetics of organic electrochemical transistors and guidelines for engineering faster organic electrochemical transistors., (© 2024. The Author(s), under exclusive licence to Springer Nature Limited.)

Conjugated polymers with ethylene glycol side chains are emerging as ideal materials for bioelectronics, particularly for application in organic electrochemical transistors (OECTs). To improve the OECT device performance, it is important to develop an efficient synthetic strategy that will provide access to novel high-performing materials besides focusing on molecular design. While a lot of efforts are being devoted to designing of new polymers by modifying the glycol side chains, understanding how their nature affects the polymerization kinetics and eventually the polymer structure and properties is not known. In this work, we have studied the influence of the content of the ethylene glycol side chain and its linkage on the formation of the active Grignard monomer species upon Grignard metathesis in three thiophene derivatives. A strong dependence of the monomer's concentration on polymerization was noted in our study indicating that for synthesizing P3MEEMT, a high-performing OECT material, by Kumada catalyst transfer polymerization (KCTP) a minimum of 0.15 M monomer is needed. Furthermore, kinetic studies by GPC show uncontrolled polymerization behavior contrary to the controlled chain growth characteristics of the KCTP.

Owing to their versatile (opto)electronic properties, conjugated polymers have found application in several organic electronic devices. Cross-coupling reactions such as Stille, Suzuki, Kumada couplings, and direct arylation reactions have proved to be effective for their synthesis. More atom-efficient oxidative direct arylation polymerization has also been reported for making homopolymers. However, growing interest toward donor-acceptor polymers has led to the recent emergence of cross-dehydrogenative coupling (CDC) polymerization to synthesize alternating copolymers without any prefunctionalization of monomers. Metal-catalyzed cross-coupling of two simple arenes via double C-H activation, or of an arene with an alkene via oxidative Heck-type reaction have been used so far for CDC polymerization. In this article, we discuss the development of CDC polymerization protocols along with the relevant small molecule CDC reactions for an improved understanding of these reactions., (© 2023 The Authors. Angewandte Chemie International Edition published by Wiley-VCH GmbH.)

Aliphatic amine and carboxylic acid ligands are widely used as organic solvents during the bottom-up synthesis of inorganic nanoparticles (NPs). Although the ligands' ability to alter final NP properties has been widely studied, side reactivity of these ligands is emerging as an important mechanism to consider. In this work, we study the thermal decomposition of common ligands with varying functional groups (amines and carboxylic acids) and bond saturations (from saturated to polyunsaturated). Here, we investigate how these ligand properties influence decomposition in the absence and presence of precursors used in NP synthesis. We show that during the synthesis of inorganic chalcogenide NPs (Cu 2 ZnSnS 4 , Cu x S, and SnS x ) with metal acetylacetonate precursors and elemental sulfur, the ligand pyrolyzes, producing alkylated graphitic species. Additionally, there was less to no ligand decomposition observed during the sulfur-free synthesis of ZnO and CuO with metal acetylacetonate precursors. These results will help guide ligand selection for NP syntheses and improve reaction purity, an important factor in many applications., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

Indacenodithiophene (IDT) copolymers are a class of conjugated polymers that have limited long-range order and high hole mobilities, which makes them promising candidates for use in deformable electronic devices. Key to their high hole mobilities is the coplanar monomer repeat units within the backbone. Poly(indacenodithiophene-benzothiadiazole) (PIDT C16 -BT) and poly(indacenodithiophene-thiapyrollodione) (PIDT C16 -TPD C1 ) are two IDT copolymers with planar backbones, but they are brittle at low molecular weight and have unsuitably high elastic moduli. Substitution of the hexadecane (C 16 ) side chains of the IDT monomer with isocane (C 20 ) side chains was performed to generate a new BT-containing IDT copolymer: PIDT C20 -BT. Substitution of the methyl (C 1 ) side chain on the TPD monomer for an octyl (C 8 ) and 6-ethylundecane (C 13B ) afford two new TPD-containing IDT copolymers named PIDT C16 -TPD C8 and PIDT C16 -TPD C13B , respectively. Both PIDT C16 -TPD C8 and PIDT C16 -TPD C13B are relatively well deformable, have a low yield strain, and display significantly reduced elastic moduli. These mechanical properties manifest themselves because the lengthened side chains extending from the TPD-monomer inhibit precise intermolecular ordering. In PIDT C16 -BT, PIDT C20 -BT and PIDT C16 -TPD C1 side chain ordering can occur because the side chains are only present on the IDT subunit, but this results in brittle thin films. In contrast, PIDT C16 -TPD C8 and PIDT C16 -TPD C13B have disordered side chains, which seems to lead to low hole mobilities. These results suggest that disrupting the interdigitation in IDT copolymers through comonomer side chain extension leads to more ductile thin films with lower elastic moduli, but decreased hole mobility because of altered local order in the respective thin films. Our work, thus, highlights the trade-off between molecular packing structure for deformable electronic materials and provides guidance for designing new conjugated polymers for stretchable electronics., Competing Interests: The authors declare no competing financial interest., (© 2022 The Authors. Published by American Chemical Society.)

Overcoming the challenges of patterning luminescent materials will unlock additive and more sustainable paths for the manufacturing of next-generation on-chip photonic devices. Electrohydrodynamic (EHD) inkjet printing is a promising method for deterministically placing emitters on these photonic devices. However, the use of this technique to pattern luminescent lead halide perovskite nanocrystals (NCs), notable for their defect tolerance and impressive optical and spin coherence properties, for integration with optoelectronic devices remains unexplored. In this work, we additively deposit nanoscale CsPbBr 3 NC features on photonic structures via EHD inkjet printing. We perform transmission electron microscopy of EHD inkjet printed NCs to demonstrate that the NCs' structural integrity is maintained throughout the printing process. Finally, NCs are deposited with sub-micrometer control on an array of parallel silicon nitride nanophotonic cavities and demonstrate cavity-emitter coupling via photoluminescence spectroscopy. These results demonstrate EHD inkjet printing as a scalable, precise method to pattern luminescent nanomaterials for photonic applications.

Organic mixed ionic electronic conductors (OMIECs) have the potential to enable diverse new technologies, ranging from biosensors to flexible energy storage devices and neuromorphic computing platforms. However, a study of these materials in their operating state, which convolves both passive and potential-driven solvent, cation, and anion ingress, is extremely difficult, inhibiting rational material design. In this report, we present a novel approach to the in situ studies of the electrochemical switching of a prototypical OMIEC based on oligoethylene glycol (oEG) substitution of semicrystalline regioregular polythiophene via grazing-incidence X-ray scattering. By studying the crystal lattice both dry and in contact with the electrolyte while maintaining potential control, we can directly observe the evolution of the crystalline domains and their relationship to film performance in an electrochemically gated transistor. Despite the oEG side-chain enabling bulk electrolyte uptake, we find that the crystalline regions are relatively hydrophobic, exhibiting little (less than one water per thiophene) swelling of the undoped polymer, suggesting that the amorphous regions dominate the reported passive swelling behavior. With applied potential, we observe that the π-π separation in the crystals contracts while the lamella spacing increases in a balanced fashion, resulting in a negligible change in the crystal volume. The potential-induced changes in the crystal structure do not clearly correlate to the electrical performance of the film as an organic electrochemical transistor, suggesting that the transistor performance is strongly influenced by the amorphous regions of the film.

Conjugated polymers (CPs) are widely used in various domains of organic electronics. However, the performance of organic electronic devices can be variable due to the lack of precise predictive control over the polymer microstructure. While the chemical structure of CPs is important, CP microstructure also plays an important role in determining the charge-transport, optical and mechanical properties suitable for a target device. Understanding the interplay between CP microstructure and the resulting properties, as well as predicting and targeting specific polymer morphologies, would allow current comprehension of organic electronic device performance to be improved and potentially enable more facile device optimization and fabrication. In this Feature Article, we highlight the importance of investigating CP microstructure, discuss previous developments in the field, and provide an overview of the key aspects of the CP microstructure-property relationship, carried out in our group over recent years.

Simple and efficient methods are a key consideration for small molecule and polymer syntheses. Direct arylation polymerization (DArP) is of increasing interest for preparing conjugated polymers as an effective approach compared to conventional cross-coupling polymerizations. As DArP sees broader utilization, advancements are needed to access materials with improved properties and different monomer structures and to improve the scalability of conjugated polymer synthesis. Presented herein are considerations for developing new methods of conjugated polymer synthesis from small molecule transformations, exploring how DArP has successfully used this approach, and presenting how emerging polymerization methodologies are developing similarly. While it is common to adapt small molecule methods to polymerizations, we demonstrate the ways in which information gained from studying polymerizations can inform and inspire greater advancements in small molecule transformations. This circular approach to organic synthetic method development underlines the value of collaboration between small molecule and polymer-based synthetic research groups.

The dimensional reduction of solids into smaller fragments provides a route to achieve new physical properties and gain deeper insight into the extended parent structures. Here, we report the synthesis of CuTOTP-OR (TOTP n - = 2,3,6,7-tetraoxidotriphenylene), a family of copper-based macrocycles that resemble truncated fragments of the conductive two-dimensional (2D) metal-organic framework Cu 3 (HHTP) 2 (HHTP = 2,3,6,7,10,11-hexahydroxytriphenylene). The planar metal-organic macrocycles self-assemble into ordered nanotubes with internal diameters of ∼2 nm and short interlayer distances of ∼3.20 Å. Strong π-π stacking interactions between macrocycles facilitate out-of-plane charge transport, and pressed pellet conductivities as high as 2(1) × 10 -3 S cm -1 are observed. Peripheral alkyl functionalization enhances solution processability and enables the fabrication of thin-film field-effect transistor devices. Ambipolar charge transport is observed, suggesting that similar behavior may be operative in Cu 3 (HHTP) 2 . By coupling the attractive features of metal-organic frameworks with greater processability, these macrocycles enable facile device integration and a more nuanced understanding of out-of-plane charge transport in 2D conductive metal-organic frameworks.

Expanding the toolbox of the biology and electronics mutual conjunction is a primary aim of bioelectronics. The organic electrochemical transistor (OECT) has undeniably become a predominant device for mixed conduction materials, offering impressive transconduction properties alongside a relatively simple device architecture. In this review, we focus on the discussion of recent material developments in the area of mixed conductors for bioelectronic applications by means of thorough structure-property investigation and analysis of current challenges. Fundamental operation principles of the OECT are revisited, and characterization methods are highlighted. Current bioelectronic applications of organic mixed ionic-electronic conductors (OMIECs) are underlined. Challenges in the performance and operational stability of OECT channel materials as well as potential strategies for mitigating them, are discussed. This is further expanded to sketch a synopsis of the history of mixed conduction materials for both p- and n-type channel operation, detailing the synthetic challenges and milestones which have been overcome to frequently produce higher performing OECT devices. The cumulative work of multiple research groups is summarized, and synthetic design strategies are extracted to present a series of design principles that can be utilized to drive figure-of-merit performance values even further for future OMIEC materials.

The Carothers equation is often used to predict the utility of a small molecule reaction in a polymerization. In this study, we present the mechanistic study of Pd/Ag cocatalyzed cross dehydrogenative coupling (CDC) polymerization to synthesize a donor-acceptor (D-A) polymer of 3,3'-dihexyl-2,2'-bithiophene and 2,2',3,3',5,5',6,6'-octafluorobiphenyl, which go counter to the Carothers equation. It is uncovered that the second chain extension cross-coupling proceeds much more efficiently than the first cross-coupling and the homocoupling side reaction (at least 1 order of magnitude faster) leading to unexpectedly low homocoupling defects and high molecular weight polymers. Kinetic analyses show that C-H bond activation is rate-determining in the first cross-coupling but not in the second cross-coupling. Based on DFT calculations, the high cross-coupling rate in the second cross-coupling was ascribed to the strong Pd-thiophene interaction in the Pd-mediated C-H bond activation transition state, which decreases the energy barrier of the Pd-mediated C-H bond activation. These results have implications beyond polymerizations and can be used to ease the synthesis of a wide range of molecules where C-H bond activation may be the limiting factor.

Bioelectronics focuses on the establishment of the connection between the ion-driven biosystems and readable electronic signals. Organic electrochemical transistors (OECTs) offer a viable solution for this task. Organic mixed ionic/electronic conductors (OMIECs) rest at the heart of OECTs. The balance between the ionic and electronic conductivities of OMIECs is closely connected to the OECT device performance. While modification of the OMIECs' electronic properties is largely related to the development of conjugated scaffolds, properties such as ion permeability, solubility, flexibility, morphology, and sensitivity can be altered by side chain moieties. In this review, we uncover the influence of side chain molecular design on the properties and performance of OECTs. We summarise current understanding of OECT performance and focus specifically on the knowledge of ionic-electronic coupling, shedding light on the significance of side chain development of OMIECs. We show how the versatile synthetic toolbox of side chains can be successfully employed to tune OECT parameters via controlling the material properties. As the field continues to mature, more detailed investigations into the crucial role side chain engineering plays on the resultant OMIEC properties will allow for side chain alternatives to be developed and will ultimately lead to further enhancements within the field of OECT channel materials., Competing Interests: The authors have no conflicts of interest., (This journal is © The Royal Society of Chemistry.)

This tutorial review presents our perspective on designing organic molecules for the functionalization of inorganic nanomaterial surfaces, through the model of an "anchor-functionality" paradigm. This "anchor-functionality" paradigm is a streamlined design strategy developed from a comprehensive range of materials ( e.g. , lead halide perovskites, II-VI semiconductors, III-V semiconductors, metal oxides, diamonds, carbon dots, silicon, etc. ) and applications ( e.g. , light-emitting diodes, photovoltaics, lasers, photonic cavities, photocatalysis, fluorescence imaging, photo dynamic therapy, drug delivery, etc. ). The structure of this organic interface modifier comprises two key components: anchor groups binding to inorganic surfaces and functional groups that optimize their performance in specific applications. To help readers better understand and utilize this approach, the roles of different anchor groups and different functional groups are discussed and explained through their interactions with inorganic materials and external environments.

A robust method of room temperature direct arylation for benzofuran is reported. This discovery allows for mild arylation by commercially available aryl iodides with complete C-2 regioselectivity and tolerates a range of functional groups, including heat sensitive groups. Mechanistically, a Heck-type oxyarylation product from a direct arylation process is reported as a key piece of evidence for a carbopalladation intermediate.

Research at the University of Washington regarding organic semiconductors is reviewed, covering four major topics: electro-optics, organic light emitting diodes, organic field-effect transistors, and organic solar cells. Underlying principles of materials design are demonstrated along with efforts toward unlocking the full potential of organic semiconductors. Finally, opinions on future research directions are presented, with a focus on commercial competency, environmental sustainability, and scalability of organic-semiconductor-based devices., (© 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The performance of electronic devices comprising conjugated polymers as the active layer depends not only on the intrinsic characteristics of the materials but also on the details of the extrinsic processing conditions. In this study, we examine the effect of postdeposition thermal treatments on the microstructure of poly(3-hexylthiophene) (P3HT) thin films and its impact on their electrical properties. Unsurprisingly, we find thermal annealing of P3HT thin films to generally increase their crystallinity and crystallite coherence length while retaining the same crystal structure. Despite such favorable structural improvements of the polymer active layers, however, thermal annealing at high temperatures can lead to a net reduction in the mobility of transistors, implicating structural changes in the intercrystallite amorphous regions of these semicrystalline active layers take place on annealing, and the simplistic picture that crystallinity governs charge transport is not always valid. Our results instead suggest tie-chain pullout, which occurs during crystal growth and perfection upon thermal annealing to govern charge transport, particularly in low-molecular-weight systems in which the tie-chain fraction is low. By demonstrating the interplay between intracrystallite and intercrystallite structuring in determining the macroscopic charge transport, we shed light on how structural evolution and charge-transport properties of nominally the same polymer can vary depending on the details of processing.

Carrier spins in semiconductor nanocrystals are promising candidates for quantum information processing. Using a combination of time-resolved Faraday rotation and photoluminescence spectroscopies, we demonstrate optical spin polarization and coherent spin precession in colloidal CsPbBr 3 nanocrystals that persists up to room temperature. By suppressing the influence of inhomogeneous hyperfine fields with a small applied magnetic field, we demonstrate inhomogeneous hole transverse spin-dephasing times ( T 2 * ) that approach the nanocrystal photoluminescence lifetime, such that nearly all emitted photons derive from coherent hole spins. Thermally activated LO phonons drive additional spin dephasing at elevated temperatures, but coherent spin precession is still observed at room temperature. These data reveal several major distinctions between spins in nanocrystalline and bulk CsPbBr 3 and open the door for using metal-halide perovskite nanocrystals in spin-based quantum technologies.

We describe an open-source and widely adaptable Python library that recognizes morphological features and domains in images collected via scanning probe microscopy. π-Conjugated polymers (CPs) are ideal for evaluating the Materials Morphology Python (m2py) library because of their wide range of morphologies and feature sizes. Using thin films of nanostructured CPs, we demonstrate the functionality of a general m2py workflow. We apply numerical methods to enhance the signals collected by the scanning probe, followed by Principal Component Analysis (PCA) to reduce the dimensionality of the data. Then, a Gaussian Mixture Model segments every pixel in the image into phases, which have similar material-property signals. Finally, the phase-labeled pixels are grouped and labeled as morphological domains using either connected components labeling or persistence watershed segmentation. These tools are adaptable to any scanning probe measurement, so the labels that m2py generates will allow researchers to individually address and analyze the identified domains in the image. This level of control, allows one to describe the morphology of the system using quantitative and statistical descriptors such as the size, distribution, and shape of the domains. Such descriptors will enable researchers to quantitatively track and compare differences within and between samples.

Plastic pollution is a threat to marine life with long term impacts to ecosystems and organisms in the sea. In this study, we quantified the presence of microparticles in wild populations of Pacific oysters (Crassostrea gigas) from the Salish Sea, Washington State. Examination under a dissecting microscope revealed 63% of oysters contained microparticles (~1.75 microparticles per oyster) and microfibers were the dominant type of particles. Using Raman microspectroscopy (RMS) and Fourier transform infrared microspectroscopy (μ-FTIR) we found that only ~2% of these microparticles were synthetic and included polymers such as polystyrene, polyethylene, polypropylene, poly(bisphenol A carbonate), rayon, and polyacrylate. It is important to note that of the 447 microparticles analyzed with RMS, 41% showed fluorescence interference, impeding the determination of their identification. The remaining microparticles were cellulose derivatives, shell fragments, biological or proteinaceous material, salts, minerals, and gypsum. Fourier transform infrared spectroscopy equipped with a diamond attenuated total reflectance accessory (ATR-FTIR) showed the presence of sorbitan derivatives in all samples examined (n = 213). These findings provide the first baseline for microplastic and other particles in oysters from the west coast of the United States integrating results from ATR-FTIR, μ-FTIR, and RMS, in addition to visual sorting. These results suggest there is low retention of plastic particles in Pacific oysters from the Salish Sea, but further research is needed to determine the composition of microparticles with fluorescence interference., Competing Interests: Declaration of competing interest The authors declare no conflict of interest., (Copyright © 2020 Elsevier B.V. All rights reserved.)

We find that conjugated polymers can undergo reversible structural phase transitions during electrochemical oxidation and ion injection. We study poly[2,5-bis(thiophenyl)-1,4-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)benzene] (PB2T-TEG), a conjugated polymer with glycolated side chains. Using grazing incidence wide-angle X-ray scattering (GIWAXS), we show that, in contrast to previously known polymers, this polymer switches between two structurally distinct crystalline phases associated with electrochemical oxidation/reduction in an aqueous electrolyte. Importantly, we show that this unique phase change behavior has important physical consequences for ion-polaron pair transport. Notably, using moving front experiments visualized by both optical microscopy and super-resolution photoinduced force microscopy (PiFM), we show that a laterally propagating ion-polaron pair front in PB2T-TEG exhibits non-Fickian transport, retaining a sharp step-edge profile, in stark contrast to the Fickian diffusion more commonly observed in polymers like P3MEEMT. This structural phase transition is reminiscent of those accompanying ion uptake in inorganic materials like LiFePO 4 . We propose that the engineering of similar properties in future conjugated polymers may enable the realization of new materials with superior performance in electrochemical energy storage or neuromorphic memory applications.

Direct arylation is an appealing method for preparing π-conjugated materials, avoiding the prefunctionalization required for traditional cross-coupling methods. A major effort in organic electronic materials development is improving the environmental and economic impact of production; direct arylation polymerization (DArP) is an effective method to achieve these goals. Room-temperature polymerization would further improve the cost and energy efficiencies required to prepare these materials. Reported herein is new mechanistic work studying the underlying mechanism of room temperature direct arylation between iodobenzene and indole. Results indicate that room-temperature, Pd/Ag-catalyzed direct arylation systems are radical-mediated. This is in contrast to the commonly proposed two-electron mechanisms for direct arylation and appears to extend to other substrates such as benzo[ b ]thiophene and pentafluorobenzene., (Copyright © 2020, Mayhugh and Luscombe; licensee Beilstein-Institut.)

The molecular morphology and dynamics of conjugated polymers in the bulk solid state play a significant role in determining macroscopic charge transport properties. To understand this relationship, molecular dynamics (MD) simulations and quantum mechanical calculations are used to evaluate local electronic properties. In this work, we investigate the importance of system and simulation parameters, such as force fields and equilibration methods, when simulating amorphous poly(3-hexylthiophene) (P3HT), a model semiconducting polymer. An assessment of MD simulations for five different published P3HT force fields is made by comparing results to experimental wide-angle X-ray scattering (WAXS) and to a broad range of quasi-elastic neutron scattering (QENS) data. Moreover, an in silico analysis of force field parameters reveals that atomic partial charges and torsion potentials along the backbone and side chains have the greatest impact on structure and dynamics related to charge transport mechanisms in P3HT.

In 2018, several major breakthroughs have been achieved in organic solar cells (OSCs) with the record power conversion efficiency (PCE) reaching over 17 %. With this increased efficiency, it is time to take a step forward to consider how to convert this technology into large scale production. For this, the economic and environmental profile of OSCs should be taken seriously-simplified synthetic routes and green chemistry methods should be applied. According to previous studies, OSCs are competitive and profitable in the commercial market. However, toxic and/or hazardous chemicals are currently used in materials synthesis and device fabrication of OSCs. In this account, we will talk about contributions and efforts we have made to minimize the economic and environmental disadvantages in the production of OSCs. We will start with the background on how our projects were conceived and will specifically discuss our work on direct arylation and green solvent. Developments of direct arylation for synthesizing conjugated polymers will be illustrated along with our recent finding regarding the effect of green solvents on device performance and stability., (© 2019 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)

We study poly(3-{[2-(2-methoxyethoxy)ethoxy]methyl}thiophene-2,5-diyl) (P3MEEMT), a new polythiophene derivative with ethylene glycol-based side chains, as a promising semiconducting polymer for accumulation-mode organic electrochemical transistors (OECTs) with figures of merit comparable to those of state-of-the-art materials. By characterizing the OECT performance of P3MEEMT transistors as a function of the anion, we find that large hydrophobic anions lower the threshold voltage. We find that, compared to poly(3-hexylthiophene-2,5-diyl) (P3HT), P3MEEMT has faster anion injection rates, which we attribute to the hydration of the P3MEEMT crystal lattice. We study P3MEEMT-based OECT and organic field-effect transistor (OFET) performance as a function of film crystallinity and show that changing the crystallinity of the polymer by thermal annealing increases the OFET mobility yet decreases the OECT mobility. We attribute this difference to the fact that, unlike OFETs, OECTs operate in aqueous environments. To probe how hydration affects the operation of OECTs, we investigate the role of water in electrochemical doping using electrochemical quartz microbalance (EQCM) gravimetry. We find that steady-state hydration and hydration dynamics under electrochemical bias differ dramatically between the crystalline and amorphous P3MEEMT films. These results suggest that the presence of water reduces the electronic connectivity between the crystalline regions of P3MEEMT, thus lowering the mobility in solution. Overall, our study highlights the importance of the role of polymer hydration and nanoscale morphology in elucidating design principles for OECT operation.

Intercrystallite molecular connections are widely recognized to tremendously impact the macroscopic properties of semicrystalline polymers. Because it is challenging to directly probe such connections, theoretical frameworks have been developed to quantify their concentrations and predict the mechanical properties that result from these connections. Tie-chain connectivity similarly impacts the electrical properties in semicrystalline conjugated polymers. Yet, its quantitative impact has eluded the community. Here, we assess the Huang-Brown model, a framework commonly used to describe the structural origins of mechanical properties in polyolefins, to quantitatively elucidate the effect of tie chains on the electrical properties of a model conjugated polymer. We found that a critical tie-chain fraction of 10 -3 is needed to support macroscopic charge transport, below which intercrystallite connectivity limits charge transport, and above which intracrystallite disorder is the bottleneck. Extending the Huang-Brown framework to conjugated polymers enables the prediction of macroscopic electrical properties based on experimentally accessible morphological parameters. Our study implicates the importance of long and rigid polymer chains for efficient charge transport over device length scales.

The functionalization of II-VI nanocrystals with semiconducting polymers is of fundamental interest for lightweight, solution-processed optoelectronics. The direct surface functionalization of nanocrystals is useful for facilitating charge transfer across the donor/acceptor interface, in addition to promoting good mixing properties and thereby helping prevent nanoparticle aggregation. In this work, we develop a new method for the direct attachment of semiconducting polymers to II-VI inorganic nanocrystals, where the polymer plays a dual role, acting as both the desired capping agent and a chalcogenide monomer during synthesis. The success of this hybridization procedure relies on the establishment of a new polymer end-functionalization scheme, where a route toward a thio-phosphonate polymer end-group is developed; this end-group resembles many chalcogenide precursor materials used in the synthesis of II-VI nanomaterials. We show the applicability of this hybrid functionalization procedure by attaching poly(3-hexylthiophene-2,5-diyl) to CdSe and CdS. We followed the progress of the reaction by NMR and used transmission electron microscopy to determine the morphology of the resulting materials, which we found to have narrow size distributions after hybridization. Polymer attachment to the nanocrystals was confirmed by examining the steady-state and time-resolved optical properties of the hybrid materials, which also provided an insight into excited-state processes occurring across the hybrid interface.

Direct arylation polymerization (DArP) has gained interest in materials chemistry as a method to synthesize conjugated polymers with minimal use of harsh reagents and additional steps. Traditional DArP conditions do not readily yield ideal polymerization characteristics, including chain-growth and low dispersities. It would be of great utility to advance DArP methodology to become competitive with traditional conjugated polymerization techniques. We have developed conditions for a dual-catalytic Ag-Pd system for the synthesis of poly(3-hexylthiophene) (P3HT) that exhibits chain-growth kinetics, low dispersities, and catalyst chain association by Pd. Specifically, the presence of Ag-carboxylate additives plays a beneficial role in the polymerization as a C-H activating agent, while PEPPSI-iPr is used as the Pd source for C-C coupling. The addition of pyridine is necessary to inhibit Pd-mediated C-H activation in the interest of catalyst orthogonality, which can lower dispersities.

Ultrasound acoustic waves are demonstrated to assemble poly-3-hexylthiophene (P3HT) chains into nanofibers after they are fully dissolved in what are commonly considered to be 'good' solvents. In the absence of ultrasound, the polymer remains fully dissolved and does not self-assemble for weeks. UV-vis spectroscopy, ultra-small angle X-ray scattering (USAXS) and small angle neutron scattering (SANS) are used to characterize the induced assembly process and to quantify the fraction of polymer that forms nanofibers. It is determined that the solvent type, insonation time, and aging periods are all important factors affecting the structure and final concentration of fibers. The effect of changing polymer regio-regularity, alkyl chain length, and side chain to thiophene ratio are also explored. High intensity focused ultrasound (HIFU) fields of variable intensity are utilized to reveal the physical mechanisms leading to nanofiber formation, which is strongly correlated to cavitation events in the solvent. This in situ HIFU cell, which is designed for simultaneous scattering analysis, is also used to probe for structural changes occurring over multiple length scales using USAXS and SANS. The proposed acoustic assembly mechanism suggests that, even when dispersed in 'good' solvents such as bromobenzene, dichlorobenzene and chloroform, P3HT chains are still not in a thermodynamically stable state. Instead, they are stabilized by local energy barriers that slow down and effectively prevent crystallization. Ultrasound fields are found to provide enough mechanical energy to overcome these barriers, triggering the formation of small crystalline nuclei that subsequently seed the growth of larger nanofibers.

Abstract : Organic electronics is a rapidly growing field driven in large part by the synthesis of ∏-conjugated molecules and polymers. Traditional aryl cross-coupling reactions such as the Stille and Suzuki have been used extensively in the synthesis of ∏-conjugated molecules and polymers, but the synthesis of intermediates necessary for traditional cross-couplings can include multiple steps with toxic and hazardous reagents. Direct arylation through C-H bond activation has the potential to reduce the number of steps and hazards while being more atom-economical. Within the Center for Selective C-H Functionalization (CCHF), we have been developing C-H activation methodology for the synthesis of ∏-conjugated materials of interest, including direct arylation of difficult-to-functionalize electron acceptor intermediates and living polymerization of ∏-conjugated polymers through C-H activation., Competing Interests: The authors declare no conflict of interest.

Ionic transport phenomena in organic semiconductor materials underpin emerging technologies ranging from bioelectronics to energy storage. The performance of these systems is affected by an interplay of film morphology, ionic transport and electronic transport that is unique to organic semiconductors yet poorly understood. Using in situ electrochemical strain microscopy (ESM), we demonstrate that we can directly probe local variations in ion transport in polymer devices by measuring subnanometre volumetric expansion due to ion uptake following electrochemical oxidation of the semiconductor. The ESM data show that poly(3-hexylthiophene) electrochemical devices exhibit voltage-dependent heterogeneous swelling consistent with device operation and electrochromism. Our data show that polymer semiconductors can simultaneously exhibit field-effect and electrochemical operation regimes, with the operation modality and its distribution varying locally as a function of nanoscale film morphology, ion concentration and potential. Importantly, we provide a direct test of structure-function relationships by correlating strain heterogeneity with local stiffness maps. These data indicate that nanoscale variations in ion uptake are associated with local changes in polymer packing that may impede ion transport to different extents within the same macroscopic film and can inform future materials optimization.

Due to their low cost and high efficiency, polymer/nanocrystal hybrid solar cells (HSCs) have attracted much attention in recent years. In this work, water-soluble hybrid materials consisting of amphiphilic block copolymers (ABCPs) and cadmium telluride nanocrystals (CdTe NCs) were used as the active layer to fabricate the HSCs via aqueous processing. The ABCPs composed of poly(3-hexylthiophene) (P3HT) and poly(acrylic acid) (PAA) self-assembled into ordered nanostructured micelles which then transformed to nanowires by comicellization with P3HT additives. Furthermore, after annealing, the hybrid materials formed an interpenetrating network which resulted in a maximum power conversion efficiency of 4.8% in the HSCs. The properties of the hybrid materials and the film morphology were studied and correlated to the device performance. The results illustrate how the inclusion of ABCPs for directed assembly and homo-P3HT for charge transport and light absorption improves device performance. The aqueous-processed HSCs based on the ABCPs and NCs offer an effective method for the fabrication of efficient solar cells.

C-H activation reactions have allowed us to react traditionally chemically inert bonds in molecules to develop new methods for cross-coupling reactions. This type of reactivity can be applied to conjugated polymer materials in an effort to improve existing synthetic difficulties including harsh reaction conditions, multiple monomer functionalization steps, and organometallic reagent waste. In this Viewpoint, we highlight some of the encouraging advances in direct arylation polymerization (DArP) as well as ongoing challenges for future improvement and utility.

Aliphatic ligands are typically used during the synthesis of nanoparticles to help mediate their growth in addition to operating as high-temperature solvents. These coordinating ligands help solubilize and stabilize the nanoparticles while in solution, and can influence the resulting size and reactivity of the nanoparticles during their formation. Despite the ubiquity of using ligands during synthesis, the presence of aliphatic ligands on the nanoparticle surface can result in a number of problems during the end use of the nanoparticles, necessitating further ligand stripping or ligand exchange procedures. We have developed a way to synthesize cadmium sulfide (CdS) nanoparticles using a unique sulfur copolymer. This sulfur copolymer is primarily composed of elemental sulfur, which is a cheap and abundant material. The sulfur copolymer has the advantages of operating both as a high temperature solvent and as a sulfur source, which can react with a cadmium precursor during nanoparticle synthesis, resulting in the generation of ligand free CdS. During the reaction, only some of the copolymer is consumed to produce CdS, while the rest remains in the polymeric state, thereby producing a nanocomposite material. Once the reaction is finished, the copolymer stabilizes the nanoparticles within a solid polymeric matrix. The copolymer can then be removed before the nanoparticles are used, which produces nanoparticles that do not have organic coordinating ligands. This nascent synthesis technique presents a method to produce metal-sulfide nanoparticles for a wide variety of applications where the presence of organic ligands is not desired.

In the search for new synthetic routes toward greener and more facile syntheses of conjugated polymers, C-H functionalization provides a promising solution by minimizing the production and processing of aryl halide monomer precursors used in traditional organometallic coupling reactions. In this paper, we investigate the use of Au(I) and its ability to directly C-H activate 2-bromo-3-hexylthiophene to form a reactive monomer species, bypassing the typical Grignard monomer formation from a dihalogenated thiophene. Addition of Pd-PEPPSI-iPr as a palladium catalyst source in the presence of the resultant aurylated thiophene monomer yielded poly(3-hexylthiophene) as observed by both NMR and GPC. Studies on the growth of these polymers show linear dependence between M n and monomer conversion, low dispersities, as well as M n predicted by catalyst loading, which is supportive of a living-type chain growth mechanism. This Au-Pd system represents a novel methodology for incorporating C-H activation into the synthesis of P3HT with control over M n .

Organic coordinating ligands are ubiquitously used to solubilize, stabilize and functionalize colloidal nanoparticles. Aliphatic organic ligands are typically used to control size during the nanoparticle growth period and are used as a high boiling point solvent for solution-based synthesis procedures. However, these aliphatic ligands are typically not well suited for the end use of the nanoparticles, so additional ligand exchange or ligand stripping procedures must be implemented after the nanoparticle synthesis. Herein we present a ligand-free CdS nanoparticle synthesis procedure using a unique sulfur copolymer. The sulfur copolymer is derived from elemental sulfur, which is a cheap and abundant material. This copolymer is used as a sulfur source and high boiling point solvent, which produces stabilized metal-sulfide nanoparticles that are suspended within a sulfur copolymer matrix. The copolymer can then be removed, thereby yielding ligand-free metal-sulfide nanoparticles.

Absorption spectroscopy is commonly utilized to probe optical properties that can be related, among other things, to the conformation of single, isolated conjugated polymer chains in solution. It is frequently suggested that changes in peak positions of optical spectra result from variations in the stiffness of polymer chains in solution because this modifies the conjugation length. In this work we utilize ultraviolet-visible (UV-vis) spectroscopy, small angle neutron scattering (SANS), and all atom molecular dynamic (AA-MD) simulations to closely probe the relationship between the conformation of single-chains of poly(3-alkylthiophene)s (P3ATs) and their optical properties. SANS results show variations in the radius of gyration and Kuhn length as a function of alkyl chain length, and structure, as well as the solvent environment. Furthermore, both SANS and MD simulations show that dissolved P3HT chains are more rigid in solvents where self-assembly and crystallization are possible. Shifts in P3AT optical properties were also observed for different solvent environments. However, these changes were not correlated to the changes in polymer conformation. Furthermore, changes in optical properties could not be perfectly described by generalized solvent-solute interactions. AA-MD simulations provide new insights into specific polymer-solvent interactions not accounted for in generalized solvatochromic theory. This work highlights the need for experiments and molecular simulations that further inform the specific role of solvent molecules on local polymer conformation and on optical properties.

Increasing global demand for energy, along with dwindling fossil fuel resources and a better understanding of the hidden costs associated with these energy sources, have spurred substantial political, academic, and industrial interest in alternative energy resources. Photovoltaics based on organic semiconductors have emerged as promising low-cost alternatives for electricity generation that relies on sunlight. In this tutorial review we discuss the relevance of these organic photovoltaics beginning with some of the economic drivers for these technologies. We then examine the basic properties of these devices, including operation and materials requirements, in addition to presenting the development of the field from a historical perspective. Potential future directions are also briefly discussed. This tutorial review is intended to be an essential overview of the progress of the field, in addition to aiding in the discussion of the future of OPV technologies.