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

Effects of Molecular Encapsulation on the Photophysical and Charge Transport Properties of a Naphthalene Diimide Bithiophene Copolymer.

Engineering the molecular structure of conjugated polymers is key to advancing the field of organic electronics. In this work, we synthesized a molecularly encapsulated version of the naphthalene diimide bithiophene copolymer PNDIT2, which is among the most popular high charge mobility organic semiconductors in n-type field-effect transistors and non-fullerene acceptors in organic photovoltaic blends. The encapsulating macrocycles shield the bithiophene units while leaving the naphthalene diimide units available for intermolecular interactions. With respect to PNDIT2, the encapsulated counterpart displays an increased backbone planarity. Molecular encapsulation prevents preaggregation of the polymer chains in common organic solvents, while it permits π-stacking in the solid state and promotes thin film crystallinity through an intermolecular-lock mechanism. Consequently, n-type semiconducting behavior is retained in field-effect transistors, although charge mobility is lower than in PNDIT2 due to the absence of the fibrillar microstructure that originates from preaggregation in solution. Hence, molecularly encapsulating conjugated polymers represent a promising chemical strategy to tune the molecular interaction in solution and the backbone conformation and to consequently control the nanomorphology of casted films without altering the electronic structure of the core polymer

Designing small molecules as ternary energy-cascade additives for polymer:fullerene solar cell blends

Ternary blends comprising an ‘energy-cascade former’ in addition to the donor and the acceptor materials increasingly attract attention in the organic solar cell area as they seem to provide a tool to positively manipulate the open-circuit voltage of bulk-heterojunction devices. By comparing two additives that have similar HOMO/LUMO levels and that can be expected to lead to an energy cascade in ternaries with the prototypical P3HT:PC60BM system, we demonstrate here that the compatibility of the additive with, in this specific case, the fullerene, that can be tailored by peripheral chemical functionalization, plays a critical role in energy cascade formation. A compromise needs to be found between good mixing (favoring energy cascade formation) and phase separation (supporting charge extraction) that affect the open-circuit voltage in an as important fashion as their electronic features, providing critical insights for future materials design activities

Designing Small Molecules as Ternary Energy-Cascade Additives for Polymer:Fullerene Solar Cell Blends

Designing Small Molecules as Ternary Energy-Cascade Additives for Polymer:Fullerene Solar Cell Blend

Influence of synthetic pathway, molecular weight and side chains on properties of indacenodithiophene-benzothiadiazole copolymers made by direct arylation polycondensation

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 similar to 10(-2) cm(2) 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 similar to 10(-1) cm(2) V-1 s(-1)