Confinement Effects on the Crystalline Features of Poly(9,9-dioctylfluorene)

Typical device architectures in polymer-based optoelectronic devices, such as field effect transistors organic light emitting diodes and photovoltaic cells include sub-100 nm semiconducting polymer thin-film active layers, whose microstructure is likely to be subject to finite-size effects. The aim of this study was to investigate effect of the two-dimensional spatial confinement on the internal structure of the semiconducting polymer poly(9,9-dioctylfluorene) (PFO). PFO melts were confined inside the cylindrical nanopores of anodic aluminium oxide (AAO) templates and crystallized via two crystallization strategies, namely, in the presence or in the absence of a surface bulk reservoir located at the template surface. We show that highly textured semiconducting nanowires with tuneable crystal orientation can be thus produced. Moreover, our results indicate that employing the appropriate crystallization conditions extended-chain crystals can be formed in confinement. The results presented here demonstrate the simple fabrication and crystal engineering of ordered arrays of PFO nanowires; a system with potential applications in devices where anisotropic optical properties are required, such as polarized electroluminescence, waveguiding, optical switching, lasing, etc

Y6 Organic Thin-Film Transistors with Electron Mobilities of 2.4 cm2 V−1 s−1 via Microstructural Tuning

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] There is a growing demand to attain organic materials with high electron mobility, μe, as current reliable reported values are significantly lower than those exhibited by their hole mobility counterparts. Here, it is shown that a well-known nonfullerene-acceptor commonly used in organic solar cells, that is, BTP-4F (aka Y6), enables solution-processed organic thin-film transistors (OTFT) with a μe as high as 2.4 cm2 V−1 s−1. This value is comparable to those of state-of-the-art n-type OTFTs, opening up a plethora of new possibilities for this class of materials in the field of organic electronics. Such efficient charge transport is linked to a readily achievable highly ordered crystalline phase, whose peculiar structural properties are thoroughly discussed. This work proves that structurally ordered nonfullerene acceptors can exhibit intrinsically high mobility and introduces a new approach in the quest of high μe organic materials, as well as new guidelines for future materials design.Ministerio de Ciencia e Innovación; PGC2018-094620-A-I00Xunta de Galicia; ED431F 2021/00

Spectroscopic techniques as tools to analyze charge transport processes in organic field effect transistors

The organic electronics research field has advanced tremendously in the last decades, already rendering semiconductors able to compete with their inorganic counterparts. However, the final blossoming of this field would probably come with the complete understanding of the charge transport mechanism in organic materials. For this end, spectroscopies techniques have been proven to be of great interest in the elucidation of the different processes taking place in electronic devices. These techniques, and in particular Raman spectroscopy is a rapid, noninvasive technique able to gather information on molecular and supramolecular levels, thus being really useful for this purpose. In this talk, some examples from our research group will be presented in which several spectroscopic techniques, supported by DFT quantum chemical calculations have been used to shed light on the charge transport mechanisms in organic field effect transistors (OFETs).Universidad de Málaga. Campus de Excelencia Internacional Andalucía Tec

Ladder-type bithiophene imide-based organic semiconductors: understanding charge transport mechanisms in organic field effect transistors

Different charge transport mechanisms at the device interface are found for a series of ladder-type semiconductors with increasing chain length

Stable and Solution-Processable Cumulenic sp-Carbon Wires: A New Paradigm for Organic Electronics

[EN] Solution-processed, large-area, and flexible electronics largely relies on the excellent electronic properties of sp(2)-hybridized carbon molecules, either in the form of pi-conjugated small molecules and polymers or graphene and carbon nanotubes. Carbon with sp-hybridization, the foundation of the elusive allotrope carbyne, offers vast opportunities for functionalized molecules in the form of linear carbon atomic wires (CAWs), with intriguing and even superior predicted electronic properties. While CAWs represent a vibrant field of research, to date, they have only been applied sparingly to molecular devices. The recent observation of the field-effect in microcrystalline cumulenes suggests their potential applications in solution-processed thin-film transistors but concerns surrounding the stability and electronic performance have precluded developments in this direction. In the present study, ideal field-effect characteristics are demonstrated for solution-processed thin films of tetraphenyl[3]cumulene, the shortest semiconducting CAW. Films are deposited through a scalable, large-area, meniscus-coating technique, providing transistors with hole mobilities in excess of 0.1 cm(2 )V(-1 )s(-1), as well as promising operational stability under dark conditions. These results offer a solid foundation for the exploitation of a vast class of molecular semiconductors for organic electronics based on sp-hybridized carbon systems and create a previously unexplored paradigm.E.G.F. acknowledges the support through the EU Horizon 2020 research and innovation program, H2020-FETOPEN-01-2018-2020 (FET-Open Challenging Current Thinking), "LION-HEARTED", grant agreement no. 828984. C.S.C. acknowledges funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program ERC-Consolidator Grant (ERC CoG 2016 EspLORE grant agreement no. 724610, website: ). R.R.T. acknowledges funding from the Natural Sciences and Engineering Research Council of Canada (NSERC) and the Canada Foundation for Innovation (CFI). This work was partially supported by the European Union's H2020-EU.4.b. - Twinning of research institutions "GREENELIT", grant agreement number 951747. GIWAXS experiments were performed at BL11 NCD-SWEET beamline at ALBA Synchrotron (Spain) with the collaboration of ALBA staff. This work was in part carried out at Polifab, the micro- and nanotechnology centre of the Politecnico di Milano. Open access funding provided by Istituto Italiano di Tecnologia within the CRUI-CARE Agreement

Polymorphism in Non-Fullerene Acceptors Based on Indacenodithienothiophene

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] 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 was 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, and 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 No. 828984. J.M and N.S. would like to thank the financial support provided by the IONBIKE RISE project, which received funding from the European Union's Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie Grant Agreement No. 823989. N.S., A.K., and A.B. furthermore are grateful to the U.S. National Science Foundation (NSF) for support via Project No. 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 No. 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.” A.I. thanks MICINN for a Personal Técnico de Apoyo contract (PTA2017-14359-I) and gratefully acknowledge the financial support of the Basque Government (Research Groups IT-1175-19) and the MICINN (PGC2018-094548-B-I00, MCIU/AEI/FEDER, UE. Funding for open access charge: Universidade da Coruña/CISUG.Gobierno Vasco; PIBA19-0051Gobierno Vasco; IT-1175-19Estados Unidos. National Science Foundation; 190590

Materials science tools for organic electronics

Organic semiconductors and their electronic applications have attracted considerable interest over the last decades promising an alternative to conventional, inorganic electronics. The extensive research in the field has led to great advances and organic electronics is now entering the stage of commercial technology. To fully exploit the touted potential of this plastic electronics platform, however, other prerequisites need now to be fulfilled: for example, good mechanical stability, ease of processing, device efficiency and reliability. Material science provides unique tools to overcome these issues, e.g. a possible approach is the employment of multicomponent systems where a combination of materials having different nature is used to obtain complex structures with enhanced properties. This thesis investigates how structure-property relationships of polymer semiconductors can be modified upon addition of other components and how electronic devices, i.e. field-effect transistors and solar cells, are affected by the multicomponent approach. By doing so, we first consider a particular class of polymer blends, based on the combination of semiconducting and insulating polymers. An analysis of the solidification processes occurring during film formation is presented and the resulting microstructures are discussed. Having established the processing recipe that allows the production of electronic devices, we then show how the electronic properties of field-effect transistors can be tailored upon blending. In particular, this thesis investigates how the blending strategy affects the stability of transistors subjected to bias-stress, the control of low subthreshold parasitic currents and charge transport ambipolarity. The multicomponent approach is then extended to other systems, in which semiconducting polymers are functionalized to form complex hybrid systems with titanium derivatives. Standard organic semiconductors, i.e. polythiophenes, are synthetized with randomly hydroxylated side-chains, which can act as reacting sites for the inorganic material. We show how the presence of the hydroxyl groups affects the doping kinetics of the semiconductor when exposed to air and, therefore, we use these materials as a model system to investigate the doping process of polythiophenes. Page | iii Having shown that blend systems can be used in electronic applications, we then investigate the relationships between three critical aspects of solution processing: the solution concentration, the resulting number of entanglements per chain in the polymer and, hence, the intermixing of different components. Different strategies have been explored in this thesis, including the employment of semiconducting:insulating polymer blends, copolymers and hybrid systems. The results of this work highlight the interplay within structure, property and processing providing guidelines on how to further develop multicomponent systems in the area of organic electronics.Open Acces

Feasibility design of an interface damper for a space borne microbalance

Feasibility design of a damper based on superelastic shape memory alloys (SMAs) is presented. The design wants to develop a passive vibration insulator for the Contamination Assessment Microbalance instrument, a quartz crystal microbalance for monitoring and measuring contamination in space environment. The ability of SMAs to act as efficient vibration insulators comes from their pseudo-elastic capabilities as the hysteretic force versus displacement behavior allows for energy dissipation. A 3D model of the instrument was developed to perform modal and dynamic random analyses aimed to identify the insulator mechanical characteristics and verify the instrument mechanical resistance. Moreover, a setup was designed to measure superelastic damping capacity of a commercial pseudoelastic shape memory alloy wire in dynamic tensile mode. The wire' specific damping capacity was then tested in different conditions, i.e. changing the excitation frequency and the amplitude of the deformation within a range of interest. The experimental activity allowed validation of the selected SMA wire for the intended application

A preliminary study on self sensing composite structures with carbon nanotubes

Dynamic measurements on carbon nanotube (CNT) multiscale glass fiber reinforced polymers (GFRPs) were performed to assess the usage of self-sensing composite structures in vibration environment. To achieve that purpose, a composite cantilever beam was tested in static and dynamic conditions. Applied strain was measured by means of strain gauges mounted on the tested specimen. Static measurements were performed to investigate linearity and repeatability of the CNT sample response. The dynamic behavior was evaluated with step sine excitation at different forcing frequencies. Preliminary results finally proved the validity and the applicability of carbon nanotubes composites to measure dynamic forcing and vibration