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The combination of computational methods and advanced characterization techniques is used to highlight the role of the intramolecular hydrogen bond in thienyldiketopyrrolopyrrole (ThDPPTh) copolyme...

Atom-economic protocols for the synthesis of poly(indacenodithiophene-alt-benzothiadiazole) (PIDTBT) are presented in which all C–C coupling steps are achieved by direct arylation. Using two different synthetic pathways, PIDTBT copolymers with different side chains (hexylphenyl, octylphenyl, dodecyl, methyl/2-octyldodecylphenyl, 2-octyldodecylphenyl/2-octyldodecylphenyl) and molecular weight (MW) are prepared. Route A makes use of direct arylation polycondensation (DAP) of indacenodithiophene (IDT) and 4,7-dibromo-2,1,3-benzothiadiazole (BTBr2) leading to PIDTBT in high yields, with adjustable MW and without indications for structural defects. Route B starts from a polyketone precursor also prepared by DAP following cyclization. While route B allows introduction of asymmetric side chains at the IDT unit, polymer analogous cyclization gives rise to defect formation. The absorption coefficient of PIDTBT with alkylphenyl side chains made by route A increases with MW. Field-effect hole mobilities around ∼10−2 cm2 V−1 s−1 are molecular weight-independent, which is ascribed to a largely amorphous thin film morphology. PIDTBT with linear dodecyl side (C12) chains exhibits a bathochromic shift (20 nm), in agreement with theory, and more pronounced vibronic contributions to absorption spectra. In comparison to alkylphenyl side chains, C12 side chains allow for increased order in thin films, a weak melting endotherm and lower energetic disorder, which altogether explain substantially higher field-effect hole mobilities of ∼ 10−1 cm2 V−1 s−1.

Molecular doping has recently been shown to improve the operating characteristics of organic photovoltaics (OPVs). Here, we prepare neutral Diquat (DQ) and use it as n-dopant to improve the perform...

Here we have investigated the influence of the molecular length and structure of a series of BTI-based semiconductors on the stabilization of charged states in solution by in situ UV/Vis/NIR spectroelectrochemistry and in the solid state, at the active interface of operational OFET devices, by charge modulation spectroscopy (CMS). Interestingly, we found that charge stabilization in the shortest system of the series (BTI2) is strongly favored via a π-dimer formation which, in addition to higher thin film microstructural ordering, results in a greater electron mobility in organic field effect transistors (OFETs). The experimental results were interpreted using TD-DFT and DFT quantum chemical calculations at different levels of theory.

Organic electronics has been steadily evolving, with improving performances, including unrivaled mechanical properties. One of the main technological trends aims at thinner and lighter form factors, toward the realization of ultraflexible and conformable large-area electronic devices, capable of withstanding harsh mechanical stresses and therefore finding applications where rigid or brittle technologies would fail. Pursuing this objective, a critical role is known to be played by the substrate, whose thickness needs to be reduced as much as possible while maintaining its processability. Ultrathin substrates and a neutral plane strategy have therefore been exploited to realize ultrathin organic devices; however, ultraflexible complementary circuits based on printed organic semiconductors, realized by means of high-throughput and large-area techniques, have not been realized so far. In this work, all-polymer organic field effect transistors and complementary inverters have been printed onto a micrometer-thin parylene substrate, subsequently also used as a top isolation layer in order to place the active components in the neutral plane of stresses. These devices show appropriate low voltage operation, with supply voltages as low as 2 V, and retain stable and uniform performances upon the application of harsh mechanical stresses, such as rolling and crumpling. These results represent the first demonstration of semi-transparent and fully organic crumpable printed electronics, and pave the way toward the realization of more complex complementary logic circuits, laying the foundation for their widespread and cost-effective integration into consumer products.

Organic solar cells incorporating non-fullerene acceptors (NFAs) have reached remarkable power conversion efficiencies of over 18%. Unlike fullerene derivatives, NFAs tend to crystallize from solutions, resulting in bulk heterojunctions that include a crystalline acceptor phase. This must be considered in any morphology-function models. Here, it is confirmed that high-performing solution-processed indacenodithienothiophene-based NFAs, i.e., ITIC and its derivatives ITIC-M, ITIC-2F, and ITIC-Th, exhibit at least two crystalline forms. In addition to highly ordered polymorphs that form at high temperatures, NFAs arrange into a low-temperature metastable phase that is readily promoted via solution processing and leads to the highest device efficiencies. Intriguingly, the low-temperature forms seem to feature a continuous network that favors charge transport despite of a poorly order along the π–π stacking direction. As the optical absorption of the structurally more disordered low-temperature phase can surpass that of the more ordered polymorphs while displaying comparable—or even higher—charge transport properties, it is argued that such a packing structure is an important feature for reaching highest device efficiencies, thus, providing guidelines for future materials design and crystal engineering activities., This work is supported by the Ministerio de Ciencia e Innovacion/FEDER (under Ref. PGC2018-094620-A-I00 and PGC2018-095411-B-I00, CEX2019-000917-S and PGC2018- 095411-B-100) and the Basque Country Government (Ref. PIBA19-0051). S.M. is grateful to POLYMAT for the doctoral scholarship. The authors thank A. Arbe, A. Alonso-Mateo, L. Hueso for their support and access to characterization tools. The authors also thank the technical and human support provided by SGIker of UPV/EHU and European funding (ERDF and ESF). GIWAXS experiments were performed at BL11 NCD-SWEET beamline at ALBA Synchrotron (Spain) with the collaboration of ALBA staff. J.M and E.F.-G. acknowledge support through the European Union's Horizon 2020 research and innovation program, H2020-FETOPEN 01- 2018-2020 (FET-Open Challenging Current Thinking), ‘LION-HEARTED', grant agreement n. 828984. J.M and N.S. would like to thank the financial support provided by the IONBIKE RISE project, which has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 823989. N.S. and A.K. and A.B. furthermore are grateful to the U.S. National Science Foundation (NSF) for support via project # 1905901 within NSF’s Division of Materials Research. A. S. and M. C. acknowledge financial support by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program “HEROIC,” grant agreement 638059. This work was partially carried out at Polifab, the micro- and nanotechnology center of the Politecnico di Milano. .C.M. thanks the Knut and Alice Wallenberg Foundation for funding through the project “Mastering Morphology for Solution-borne Electronics”.

Structural defects in semiconducting conjugated polymers are usually suspected to deteriorate their properties and device performance and therefore complicate batch-to-batch reproducibility. This s...

Substrate engineering for steering cell growth is a wide and well-established area of research in the field of modern biotechnology. Here we introduce a micromachining technique to pattern an inert, transparent polymer matrix blended with a photoactive polymer. We demonstrate that the obtained scaffold combines the capability to align with that to photostimulate living cells. This technology can open up new and promising applications, especially where cell alignment is required to trigger specific biological functions, e.g. generate powerful and efficient muscle contractions following an external stimulus., Comment: 30 pages, 7 images in main text, 5 images in supporting

It is well established that for organic photodetectors (OPDs) to compete with their inorganic counterparts, low dark currents at reverse bias must be achieved. Here, two rhodanine-terminated nonfullerene acceptors O-FBR and O-IDTBR are shown to deliver low dark currents at -2 V of 0.17 and 0.84 nA cm-2, respectively, when combined with the synthetically scalable polymer PTQ10 in OPD. These low dark currents contribute to the excellent sensitivity to low light of the detectors, reaching values of 0.57 μW cm-2 for PTQ10:O-FBR-based OPD and 2.12 μW cm-2 for PTQ10:O-IDTBR-based OPD. In both cases, this sensitivity exceeds that of a commercially available silicon photodiode. The responsivity of the PTQ10:O-FBR-based OPD of 0.34 AW-1 under a reverse bias of -2 V also exceeds that of a silicon photodiode. Meanwhile, the responsivity of the PTQ10:O-IDTBR of 0.03 AW-1 is limited by the energetic offset of the blend. The OPDs deliver high specific detectivities of 9.6 × 1012 Jones and 3.3 × 1011 Jones for O-FBR- and O-IDTBR-based blends, respectively. Both active layers are blade-coated in air, making them suitable for high-throughput methods. Finally, all three of the materials can be synthesized at low cost and on a large scale, making these blends good candidates for commercial OPD applications.

Organic mixed conductors find use in batteries, bioelectronics technologies, neuromorphic computing, and sensing. While great progress has been achieved, polymer-based mixed conductors frequently experience significant volumetric changes during ion uptake/rejection, i.e., during doping/de-doping and charging/discharging. Although ion dynamics may be enhanced in expanded networks, these volumetric changes can have undesirable consequences, e.g., negatively affecting hole/electron conduction and severely shortening device lifetime. Here, the authors present a new material poly[3-(6-hydroxy)hexylthiophene] (P3HHT) that is able to transport ions and electrons/holes, as tested in electrochemical absorption spectroscopy and organic electrochemical transistors, and that exhibits low swelling, attributed to the hydroxylated alkyl side-chain functionalization. P3HHT displays a thickness change upon passive swelling of only +2.5%, compared to +90% observed for the ubiquitous poly(3,4-ethylenedioxythiophene):polystyrene sulfonate, and +10 to +15% for polymers such as poly(2-(3,3'-bis(2-(2-(2-methoxyethoxy)ethoxy)ethoxy)-[2,2'-bithiophen]-5-yl)thieno[3,2-b]thiophene) (p[g2T-TT]). Applying a bias pulse during swelling, this discrepancy becomes even more pronounced, with the thickness of P3HHT films changing by10% while that of p(g2T-TT) structures increases by +75 to +80%. Importantly, the initial P3HHT film thickness is essentially restored after de-doping while p(g2T-TT) remains substantially swollen. The authors, thus, expand the materials-design toolbox for the creation of low-swelling soft mixed conductors with tailored properties and applications in bioelectronics and beyond.

Carbyne and linear carbon structures based on sp-hybridization are attractive targets as the ultimate one-dimensional system (i.e., one-atom in diameter) featuring wide tunability of optical and electronic properties. Two possible structures exist for sp-carbon atomic wires: (a) the polyynes with alternated single-triple bonds and (b) the cumulenes with contiguous double bonds. Theoretical studies predict semiconducting behavior for polyynes, while cumulenes are expected to be metallic. Very limited experimental work, however, has been directed toward investigating the electronic properties of these structures, mostly at the single-molecule or monolayer level. However, sp-carbon atomic wires hold great potential for solution-processed thin-film electronics, an avenue not exploited to date. Herein, we report the first field-effect transistor (FET) fabricated employing cumulenic sp-carbon atomic wires as a semiconductor material. Our proof-of-concept FET device is easily fabricated by solution drop casting and paves the way for exploiting sp-carbon atomic wires as active electronic materials.

Chemical design criteria for materials for bioelectronics applications using a series of copolymer derivatives based on poly(3-hexylthiophene) are established. Directed chemical design via side-chain functionalization with polar groups allows manipulation of ion transport and ion-to-electron transduction. Insights gained will permit increased use of the plethora of materials employed in the organic electronics area for application in the bioelectronics field.

Indacenodithiophene (IDT) based materials are emerging high performance conjugated polymers for use in efficient organic photovoltaics and transistors. However, their preparation generally suffers from long reaction sequences and is often accomplished using disadvantageous Stille couplings. Herein, we present detailed synthesis pathways to IDT homopolymers using C-H activation for all C-C coupling steps. Polyketones are first prepared by direct arylation polycondensation (DAP) in quantitative yield and further cyclized polymer analogously. This protocol is suitable for obtaining structurally well-defined IDT homopolymers, provided that the conditions for cyclization are chosen appropriately and that side reactions are suppressed. Moreover, this polymer analogous pathway gives rise to asymmetric side chain patterns, which allows to fine tune physical properties. Alternatively, IDT homopolymers can be obtained via oxidative direct arylation polycondensation of IDT monomers (oxDAP), leading to IDT homopolymers with similar properties but at reduced yield. Detailed characterization by NMR, IR, UV-vis and PL spectroscopy, and thermal properties, is used to guide synthesis and to explain varying field-effect transistor hole mobilities in the range of 10-6- 10-3 cm2/Vs.

The addition of a third component to a donor:acceptor blend is a powerful tool to enhance the power conversion efficiency of organic solar cells. Featuring a similar operating mechanism, organic photodetectors are also expected to benefit from this approach. Here, we fabricated ternary organic photodetectors, based on a polymer donor and two nonfullerene acceptors, resulting in a low dark current of 0.42 nA cm−2 at −2 V and a broadband specific detectivity of 1012 Jones. We found that exciton recombination in the binary blend is reduced in ternary devices due to the formation of a pseudo-binary microstructure with mixed donor–acceptor phases. With this approach a wide range of intermediate open-circuit voltages is accessible, without sacrificing light-to-current conversion. This results in ternary organic photodetector (TOPD) with improved Responsivity values in the near-infrared. Moreover, morphology analyses reveal that TOPD devices showed improved microstructure ordering and consequentially higher charge carrier mobilities compared to the reference devices.