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Polymer crystalsomes are a class of hollow crystalline polymer nanoparticles with shells formed by single crystals with broken translational symmetry. They have shown intriguing mechanical, thermal, and biomedical properties associated with spherical packing. Previously reported crystalsomes are formed by quasi-2D lamellae which can readily tile on a spherical surface. In this work, the formation of polymer crystalsomes formed by 1D polymer crystals is reported. Poly (3-hexylthiophene) (P3HT) is chosen as the model polymer because of its 1D growth habit. P3HT crystalsomes are successfully fabricated using a miniemulsion solution crystallization method, as confirmed by scanning electron microscopy and transmission electron microscopy. X-ray diffraction (XRD) and selected area electron diffraction experiments confirm that P3HT crystallized into a Form I crystal structure. XRD, differential scanning calorimetry and UV-Vis results reveal curvature-dependent structural, thermal and electro-optical properties., (© 2022 Wiley-VCH GmbH.)

Molecular ordering of conjugated polymers both in solution-state aggregates and in solid-state microstructures is a determining factor of the charge transport properties in optoelectronic devices. However, the effect of backbone conformation in conjugated polymers on assembly structures is still unclear. Herein, to understand such backbone conformation effect, three novel chlorinated benzodifurandionge-based oligo(p-phenylene vinylene) (BDOPV) polymers are systematically developed. These BDOPV-based polymers exhibit significantly twisted backbone conformation (near 90° interunit torsion angle) between conjugated units, which can prevent polymer chains from forming ordered assembly structures by increasing conformational energy penalty in closely packed chains. A higher rotational barrier of the torsion angle would further prevent polymer chains from assembling, finally resulting in nonaggregated chains in solution and highly disordered solid-state packing structures. This work will deepen the understanding of the relationship between polymer backbone conformation and assembly structures, contributing to the exploration of the structure-property relationship of polymers., (© 2022 Wiley-VCH GmbH.)

Polythiophene‐based conjugated polyelectrolytes (CPE) are attracting increasing attention as sensor or interface materials in chemistry and biology. While cationic polythiophenes are better understood, limited structural information is available on their anionic counterparts. Limited access to well‐defined polymers has made the study of structure‐property relationships difficult and clear correlations have remained elusive. By combining controlled Kumada catalyst transfer polymerization with a polymer‐analog substitution, regioregular and narrowly distributed poly(6‐(thiophen‐3‐yl)hexane‐1‐sulfonate)s (PTHS) with tailored chain length are prepared. Analysis of their aqueous solution structures by small‐angle neutron scattering (SANS) revealed a cylindrical conformation for all polymers tested, with a length close to the contour length of the polymer chains, while the estimated radii remain too small (<1.5 nm) for extensive π‐stacking of the chains. The latter is particularly interesting as the longest polymer exhibits a concentration‐independent structured absorption typical of crystalline polythiophenes. Increasing the ionic strength of the solution diminishes these features as the Coulomb repulsion between the charged repeat units is shielded, allowing the polymer to adopt a more coiled conformation. The extended π‐conjugation, therefore, appears to be a key parameter for these unique optical features, which are not present in the corresponding cationic polythiophenes. [ABSTRACT FROM AUTHOR]

Tailoring the crystal orientation of donor–acceptor (D–A) copolymers is vital for boosting the performance of optoelectronic devices. Despite recent advances in controlling the crystal orientation of D–A copolymers in films, the investigation into their aggregates in solution and the correlation between the solution aggregates and solid‐state crystal orientation has been limited. Herein, an effective solvent additive strategy is reported for tuning solution aggregates and the consequent solid‐state structures of poly{[N,N'‐bis(2‐octyldodecyl)‐naphthalene‐1,4,5,8‐bis(dicarboximide)‐2,6‐diyl]‐alt‐5,5′‐(2,2′‐bithiophene)} (P(NDI2OD‐T2)). Specifically, the addition of 1‐decanethiol (10‐thiol) to the P(NDI2OD‐T2) chloroform solution promoted the aggregation of P(NDI2OD‐T2) chains because of the improved planarization of the backbones, which changed their crystal orientation in the film from coexisting edge‐on and face‐on to dominant edge‐on when produced by drop‐casting. The mechanism of this crystal orientation transformation is elucidated based on the interaction between 10‐thiol and the side chains of P(NDI2OD‐T2). The optical properties of P(NDI2OD‐T2) films with different crystalline structures are closely correlated. Notably, the 10‐thiol‐enabled facile tailoring of the crystal orientation in P(NDI2OD‐T2) can be readily applied to other D–A copolymers of interest. The findings of this study highlight a robust solvent additive strategy for regulating solution aggregates and crystal orientation in D–A copolymer films, which have applications in many optoelectronic devices. [ABSTRACT FROM AUTHOR]

Singlet fission (SF) is a spin–allowed process in which a higher–energy singlet exciton is converted into two lower‐energy triplet excitons via a triplet pair intermediate state. Implementing SF in photovoltaic devices holds the potential to exceed the Shockley–Queisser limit of conventional single‐junction solar cells. Although great progress has been made in exploiting the underlying mechanism of SF over the past decades, the scope of materials capable of SF, particularly polymeric materials, remains poor. SF–capable polymer is one of the most potential candidates in the implementation of SF into devices due to their distinct superiorities in flexibility, solution processability and self‐assembly behavior. Notably, recent advancements have demonstrated high‐performance SF in isolated donor‐acceptor (D‐A) copolymer chains. This review provides an overview of recent progress in the development of SF‐capable polymeric materials, with a significant focus on elucidating the mechanisms of SF in polymers and optimizing the design strategies for SF‐capable polymers. Additionally, the paper discusses the challenges encountered in this field and presents future perspectives. It is expected that this comprehensive review will offer valuable insights into the design of novel SF‐capable polymeric materials, further advancing the potential for SF implementation in photovoltaic devices. [ABSTRACT FROM AUTHOR]

Circularly polarized luminescence (CPL) materials with clustering‐triggered emission (CTE) characteristic have gradually attracted attention for their unique photophysical properties. However, the majority of reported clusteroluminogens lack chirality and exhibit heterogeneity, making it challenging to achieve a well‐defined helical structure necessary for efficient CPL with high dissymmetry factor (glum). In this paper, chiral liquid crystals are constructed to obtain CTE‐based CPL materials with high glum values. Side chain liquid crystal polymer PM6Chol bearing cholesterol clusteroluminogens are designed and synthesized. PM6Chol‐coated film and PM6Chol thermal‐treated film are also successfully prepared by different film‐forming methods. Both the films inherit the CTE characteristic of cholesterol and show excitation wavelength‐dependent luminescent behavior. However, the two polymer films exhibit different liquid crystal phase structures, with PM6Chol‐coated film being a chiral bilayer smectic C phase and PM6Chol thermal‐treated film being an achiral bilayer smectic A phase. Attributed to helical arrangement of cholesterol, PM6Chol‐coated film emits efficient CPL with glum values up to 1.0 × 10−1. For PM6Chol thermal‐treated film, no CPL signal is detected due to the absence of helical structure. However, it shows obvious room‐temperature phosphorescence with 2.0 s afterglow and 23.9 ms lifetime. [ABSTRACT FROM AUTHOR]

The molecular order and vertical component distribution are critical to enhance the charge transport in layer‐by‐layer (LbL) processed active layer. However, the excessive inter‐diffusion between donor and acceptor layers during LbL processing irrepressibly reduces their ordered packing. Herein, a novel tactic to optimize the molecular order and vertical morphology of the active layer through suppressing the deep penetration of (5Z,5′Z)‐5,5′‐((7,7′‐(4,4,9,9‐tetraoctyl‐4,9‐dihydro‐s‐indaceno[1,2‐b:5,6 ‐b′]dithiophene‐2,7‐diyl)bis(benzo[c][1,2,5]thiadiazole‐7,4‐diyl))bis(methanylylidene)) bis(3‐ethyl‐2‐thioxothiazolidin‐4‐one) (O‐IDTBR) to poly(3‐hexylthiophene) (P3HT) film during LbL processing is proposed. This is enabled by inducing the formation of P3HT nanofibers through ultraviolet (UV) irradiation and solution aging. During the LbL processing, these nanofibers with high crystallinity reduce the damage of O‐IDTBR solution to P3HT film and restrict the penetration of O‐IDTBR into P3HT matrix. As a result, the P3HT nanofibers are preserved and the degree of vertical phase separation is enlarged in the LbL‐processed film. Meanwhile, the molecular order of both components is enhanced. The resulting morphology that featured as intertwined P3HT nanofibers/O‐IDTBR network efficiently promotes charge transport and extraction, boosting the power conversion efficiency (PCE) of the devices from 6.70 ± 0.12% to 7.71 ± 0.10%. [ABSTRACT FROM AUTHOR]

The development of n-type polymers for organic electrochemical transistors (OECTs) has lagged significantly behind their p-type counterparts. Moreover, these polymers are often synthesized via Stille polycondensation. Herein, three polymers with thiazole-flanked diketopyrrolopyrrole is synthesized as the monomer through C─H/C─H oxidative direct arylation polycondensation (Oxi-DArP). This protocol employs unfunctionalized (C─H terminated) monomers, and the generated byproducts are environmentally benign. The electron-deficient polymer backbone confers these polymers with LUMO energy levels below -4.20 eV, enabling all of them to exhibit n-type behavior in OECTs. Additionally, the resulting polymers are soluble in the green solvent anisole. With an optimized alkyl spacer between oligo(ethylene glycol) side chain and conjugated backbone, the polymer gTzDPP-C8 showed the best device performance with geometry normalized transconductance (g m,norm ) up to 6.31 S cm -1 and µC * up to 23.1 F V -1  cm -1 s -1 . This work has successfully proved that C─H/C─H Oxi-DArP is a promising method for synthesizing n-type OMIECs to fulfill high-performance OECTs., (© 2024 Wiley‐VCH GmbH.)

Responsive chiral optical materials have gained considerable interests from the fields of sensing, display, and optical devices. Materials that are capable of changing chiral optics under harsh conditions such as strong basic/acidic or ultrahigh temperature provides thoughts for the design of materials working at special environments, which however, are still underdeveloped. Here, a proof-of-concept design of organogel is reported that acts as matrices for thermal chiroptical switch with critical working temperature above 100 °C. The reversible solution-to-gel transition of the specific β-cyclodextrin/dimethyl formide/LiCl system is initialized at about 130 °C, when the luminophores with aggregation-induced-emission property shall be lighted up with transferred chirality from inherent chiral β-cyclodextrin. It allows for the controlled emergence of circularly polarized luminescence. This delicate design enables successful fabrication of ultrahigh temperature thermal chiroptical switch., (© 2024 Wiley‐VCH GmbH.)

Blends of semiconducting (SC) and ferroelectric (FE) polymers have been proposed for applications in resistive memories and organic photovoltaics (OPV). For OPV, the rationale is that the local electric field associated with the dipoles in a blend could aid exciton dissociation, thus improving power conversion efficiency. However, FE polymers either require solvents or processing steps that are incompatible with those required for SC polymers. To overcome this limitation, SC (poly(3-hexylthiophene)) and FE (poly(vinylidene fluoride-trifluoroethylene)) components are incorporated into a block copolymer and thus a path to a facile fabrication of smooth thin films from suitably chosen solvents is achieved. In this work, the photophysical properties and device performance of organic solar cells containing the aforementioned block copolymer consisting of poly(vinylidene fluoride-trifluoroethylene): P(VDF-TrFE), poly(3-hexylthiophene): P3HT and the electron acceptor phenyl-C 61 -butyric acid methyl ester: [60]PCBM are explored. A decrease in photovoltaic performance is observed in blends of the copolymer with P3HT:[60]PCBM, which is attributed to a less favorable nanomorphology upon addition of the copolymer. The role of lithium fluoride (the cathode modification layer) is also clarified in devices containing the copolymer, and it is demonstrated that ferroelectric compensation prevents the ferroelectricity of the copolymer from improving photovoltaic performance in SC-FE blends., (© 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.)

The intra and intermolecular interactions (J‐ and H‐type aggregation) in the conjugated polymer films are found to readily facilitate the electron and hole transport, respectively. However, how those different aggregation types influence the photocurrent generation at the heterojunction is still mysterious, especially for the newly developed semicrystalline conjugated polymers. Here, the prototypical copolymer PM6 is used to tune the relative content of aggregation types with various halogen‐free processing solvents. Various measurements reveal that the toluene‐processed PM6 film exhibits the increased H‐aggregates and crystallinity in the π–π stacking direction compared to its o‐xylene‐ and trimethylbenzene (TMB)‐processed counterparts. This is partly resulted from the weak steric effect and good solubility in the PM6 solution prepared with toluene, which strengthens the intermolecular interaction of adjacent polymer segments. After analyzing the photovoltaic properties of PM6/Y6 bilayer devices, the faster charge carrier transport, smaller charge recombination, lower energy losses, and interfacial energetic disorder can be observed in the toluene‐processed device, leading to the synergistically improved short‐circuit current density (JSC) and open‐circuit voltage (VOC). These findings indicate the control of the molecular packing structure in terms of aggregation types is a powerful strategy to promote the photocurrent generation process at the conjugated polymer‐based heterojunction. [ABSTRACT FROM AUTHOR]

The development of conjugated polymers with structures that are suitable for efficient molecular doping and charge transport is a key challenge in the construction of high‐performance conjugated polymer‐based thermoelectric devices. In this study, three novel conjugated polymers based on dithienopyrrole (DTP) are synthesized and their thermoelectric properties are compared. When doped with p‐dopant, a donor–acceptor type copolymer, DPP‐MeDTP, exhibits higher electrical conductivity and thermoelectric power factor compared to the other donor–donor type copolymers. The high electrical conductivity of DPP‐MeDTP compared to the other polymers originates from the high degree of backbone planarity and molecular order, which contributes to its high charge carrier mobility. In addition, the highly crystalline structure of DPP‐MeDTP is well maintained upon doping, while the crystalline order of the other polymers decreases significantly upon doping. The findings of this work not only provide insights into the design of DTP‐based conjugated polymers for thermoelectric use but also demonstrate the significance of a high degree of molecular order and structural robustness upon doping to achieve high thermoelectric performance. [ABSTRACT FROM AUTHOR]

Singlet fission (SF) is a spin‐allowed process in which a singlet state splits into two triplet states. Materials that enable SF have attracted great attention in the last decade, mainly stemming from the potential of overcoming the Shockley–Queisser (SQ) limit in photoenergy conversion. In the past decade, a large number of new molecules exhibiting SF are explored and many devices based on SF materials are studied, though the mechanistic understanding is still obscure. This review focuses on the recent developments of SF materials, including small molecules, oligomers, and polymers. The molecular design strategies and related mechanisms of SF are discussed. Then the dynamics of charge transfer and energy transfer between SF materials and other materials are introduced. Further, the progresses of implementing SF in photovoltaics are discussed. It is hoped that a comprehensive understanding to the SF materials, devices, and mechanism may pave a new way for the design of next generation photovoltaics. [ABSTRACT FROM AUTHOR]

Singlet fission (SF) is a spin-allowed process in which a higher-energy singlet exciton is converted into two lower-energy triplet excitons via a triplet pair intermediate state. Implementing SF in photovoltaic devices holds the potential to exceed the Shockley-Queisser limit of conventional single-junction solar cells. Although great progress has been made in exploiting the underlying mechanism of SF over the past decades, the scope of materials capable of SF, particularly polymeric materials, remains poor. SF-capable polymer is one of the most potential candidates in the implementation of SF into devices due to their distinct superiorities in flexibility, solution processability and self-assembly behavior. Notably, recent advancements have demonstrated high-performance SF in isolated donor-acceptor (D-A) copolymer chains. This review provides an overview of recent progress in the development of SF-capable polymeric materials, with a significant focus on elucidating the mechanisms of SF in polymers and optimizing the design strategies for SF-capable polymers. Additionally, the paper discusses the challenges encountered in this field and presents future perspectives. It is expected that this comprehensive review will offer valuable insights into the design of novel SF-capable polymeric materials, further advancing the potential for SF implementation in photovoltaic devices., (© 2023 Wiley-VCH GmbH.)

Two D‐A copolymers consisting of fused ring pyrrolo‐dithieno‐quinoxaline acceptors are synthesized with different donor units, i.e., benzodithiophene (BDT) with alkylthienyl (P134) and 2‐ethylhexyloxy (P117) side chains. These copolymers are used as donors and a narrow bandgap acceptor Y6 to fabricate bulk heterojunction polymer solar cell devices. Owing to the strong electron‐deficient fused ring pyrrolo‐bithieno‐quinoxaline and weak alkyl thienyl side chains in BDT, the polymer solar cells (PSCs) based on P134:Y6 attain the power conversion efficiency (PCE) of 15.42%, which is higher than the P117:Y6 counterpart (12.14%). The superior value of PCE for P134:Y6 can be associated with more well‐adjusted charge transport, weak charge recombination, proficient exciton generation, and dissociation into free charge carriers and their subsequent charge collection owing to the dense π–π stacking distance and more considerable crystal coherence length for the P134:Y6 thin films. This investigation confirms the great potential of a strong acceptor‐weak donor tactic for developing efficient D‐A copolymers consists of quinoxaline acceptor for PSCs. [ABSTRACT FROM AUTHOR]

Abstract: A new class of conjugated polymers with high charge mobilities exhibits the apparently conflicting morphological features of increased order at the molecular scale while lacking long‐range order and crystallinity. To exploit their unique properties, mechanistic insights for charge transport events taking place from the molecular to the device scale must be uncovered. Thus, a central contributor to the continued progress in conjugated optoelectronic materials will be the development of advanced characterization tools, particularly those targeted to measuring the charge‐transfer processes in heterogeneous, anisotropic, and hierarchically structured materials. This feature article describes the morphological properties that make partially ordered polymers an intriguing materials system to explore connections between chemical identity, solid‐phase microstructure, and hierarchical charge transport. To this end, recent directions in materials development and new opportunities for characterization are discussed. [ABSTRACT FROM AUTHOR]

Abstract: Three novel copolymers based on zigzag naphthodithiophene (zNDT) with different aromatic rings as π bridges and different core side substitutions are designed and synthesized (PzNDT‐T‐1,3‐bis(4‐(2‐ethylhexyl)‐thiophen‐2‐yl)‐5,7‐bis(2‐ethylhexyl)benzo[1,2‐c:4,5‐c′]‐dithiophene‐4,8‐dione (BDD), PzNDT‐TT‐BDD, and PzNDTP‐T‐BDD, respectively). The 2D conjugation structure and molecular planarity of the polymers can be effectively altered through the modification of conjugated side chains and π‐bridges. These alterations contribute to the variation in energy levels, light absorption capacity, and morphology compatibility of the polymers. When blended with the nonfullerene acceptor (2,2′‐[(4,4,9,9‐tetrahexyl‐4,9‐dihydro‐sindaceno[1,2‐b:5,6‐b′]dithiophene‐2,7‐diyl)bis[methylidyne(3‐oxo‐1H‐indene‐2,1(3H)‐diylidene)]]bis‐propanedinitrile) (IDIC), PzNDT‐T‐BDD exhibits the highest power conversion efficiency (PCE) of 9.72% among the three polymers. This result can be attributed to its superior crystallinity and more obvious face‐on orientation in blending film. PzNDT‐TT‐BDD and PzNDTP‐T‐BDD present PCE values of 8.20% and 4.62%, respectively. The alteration of polymer structure, particularly the modification of conjugated side chains and π‐bridges, is an effective strategy for designing NDT‐based polymers with high photovoltaic performance and potential applications in fullerene‐free solar cells. [ABSTRACT FROM AUTHOR]

Abstract: An intriguing morphological transition from poly(3‐hexylthiophene) (P3HT) 1D nanofibers to 2D nanoribbons enabled by the addition of a series of alkylthiols is reported. First, P3HT 1D nanofibers are formed due to strong anisotropic π–π stacking between planar rigid backbones. Upon the addition of alkylthiols, P3HT nanofibers are transformed into nanoribbons associated with the crystallographic transition from edge‐on orientation to flat‐on orientation. The content of alkylthiols has a great influence on the P3HT morphology in the solution. The mechanism of such a morphological transformation is discussed based on the interaction between alkylthiols and P3HT chains. This work offers an effective strategy to tailor the crystal morphology and dimension of P3HT, which not only improves the understanding of P3HT crystallization but also may enable such discovery into conjugated polymer‐based optoelectronic devices. [ABSTRACT FROM AUTHOR]

For a singlet-triplet coupled molecular system, the efficiency of forward and reverse intersystem crossing processes can be enhanced by reducing the energy gap between the singlet and triplet excited states (Δ EST), thus prolonging the exciton lifetimes. This has been proven beneficial for many emerging applications such as molecular luminescence, optoelectronics, and photonics. Here, a strategy is proposed to create small Δ EST by polymerizing fluorescent dye molecules, the efficacy of which is justified by density functional theory calculations and ultrafast spectroscopy. Thus, singlet-triplet exciton communication through polymerization-enhanced intersystem crossing is also proposed. [ABSTRACT FROM AUTHOR]

A zoo of chemical structures is accessible when the branched unit 2,2′:3',2″-terthiophene (3T) is included both in structurally well-defined small molecules and polymer-like architectures. The first part of this review article highlights literature on all-thiophene based branched oligomers including dendrimers as well as combinations of 3T-units with functional moieties for light-harvesting systems. Motivated by the perfectly branched macromolecular dendrimers both electropoly­merization as well as chemical approaches are presented as methods for the preparation of branched polythiophenes with different branching densities. Structure-function relationships between the molecular architecture and optical and electronic properties are discussed throughout the article. [ABSTRACT FROM AUTHOR]

Until recently π-conjugated organic materials are based mainly on linear systems. Recent years, however, have brought about increasing interest in molecules boasting a dendritic, branched, or star-shaped architecture. This tendency is a direct result of the ongoing search for materials with progressively better properties. Such compounds, featuring novel, 3D architectures, exhibit a multitude of interesting qualities, making them stand out from well-known materials. The direction of star-shaped compound application is determined by whether they are able to form aggregates, π-stacks. This feature is a source of some astounding properties, coveted in numerous applications. Among this class of compounds high charge mobility, high fluorescence efficiency, and good charge separation are all found. Depending on the structure of the core, the molecule may adopt various types of symmetry. Similarly, the conjugation of orbitals may extend over the whole structure or be interrupted at chosen segments. The number of papers pertaining to star-shaped oligomers and polymers is ascending with each year, evidencing a growing interest in them. Consequently, this Review focuses particularly on the most recent reports concerning modification of the structure and properties of the aforementioned type of compounds, as well as on the development of devices based on them. [ABSTRACT FROM AUTHOR]

Treatment of a Ni-terminated poly(3-hexylthiophene) (P3HT), generated in situ from 5-chloromagnesio-2-bromo-3-hexylthiophene and Ni(1,3-bis(diphenylphosphino)propane)Cl2, with a perylene diimide-functionalized arylisocyanide monomer effects a chain-extension polymerization to afford a donor-acceptor diblock copolymer using a single catalyst and in a single reaction vessel. The two mechanistically distinct polymerizations proceed in a controlled, chain growth fashion, allowing the molecular weight of both the P3HT and poly(isocyanide) blocks to be tuned by adjusting the initial monomer-to-catalyst ratios. The resulting materials are found to self-assemble into crystalline, lamellar stacks of donor and acceptor components in the solid state, and also exhibit fluorescence quenching in thin films, properties which poise these materials for use in organic photovoltaic applications. [ABSTRACT FROM AUTHOR]

Poly(3-heptylselenophene)- stat-poly(3-hexylthiophene) is synthesized and characterized in terms of its crystallinity and performance in an organic photovoltaic (OPV) cell. Despite the random distribution of units along the polymer main chain, the material is semi-crystalline, as demonstrated by differential scanning calorimetry and wide-angle X-ray diffraction. Thin-film absorption suggests an increased compatibility than seen with 3-hexylselenophene monomer. Optoelectronic properties are an average of the two homopolymers, and OPV performance is enhanced by a broadened absorption profile and a favorable morphology. [ABSTRACT FROM AUTHOR]

A series of conjugated polymers comprising polythiophene, polyselenophene, and polytellurophene with branched 3,7‐dimethyloctyl side chains, well‐matched molecular weight, dispersity, and regioregularity is synthesized. The ionization potential is found to vary from 5.14 to 5.32 eV, with polytellurophene having the lowest potential. Field‐effect transistors based on these materials exhibit distinct hole transport mobility that varies by nearly three orders of magnitude, with polytellurophene having the highest mobility (2.5 × 10−2 cm² V−1 s−1). The large difference in mobility demonstrates the significant impact of heteroatom substitution. Although the series of polymers are very similar in structure, their solid‐state properties are different. While the thin film microstructure of polythiophene and polyselenophene is identical, polytellurophene reveals globular features in the film topography. Polytellurophenes also appear to be the least crystalline, even though their charge transport properties are superior to other samples. The torsional barrier and degree of planarity between repeat units increase as one moves down group‐16 elements. These studies show how a single atom in a polymer chain can have a substantial influence on the bulk properties of a material, and that heavy group‐16 atoms have a positive influence on charge transport properties when all other variables are kept unchanged. Polythiophene, polyselenophene, and polytellurophene with an identical side chain are prepared with well‐matched molecular weight, dispersity, and regioregularity. One single atom change in a polymer chain is shown to have a substantial impact on the properties of these materials. Polytellurophene appears to be the least crystalline but exhibits the highest mobility in field‐effect transistors. [ABSTRACT FROM AUTHOR]