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    Ultrasoft and High-Mobility Block Copolymers for Skin-Compatible Electronics
    (Weinheim : Wiley-VCH, 2020) Ditte, Kristina; Perez, Jonathan; Chae, Soosang; Hambsch, Mike; Al-Hussein, Mahmoud; Komber, Hartmut; Formanek, Peter; Mannsfeld, Stefan C.B.; Fery, Andreas; Kiriy, Anton; Lissel, Franziska
    Polymer semiconductors (PSCs) are an essential component of organic field-effect transistors (OFETs), but their potential for stretchable electronics is limited by their brittleness and failure susceptibility upon strain. Herein, a covalent connection of two state-of-the-art polymers—semiconducting poly-diketo-pyrrolopyrrole-thienothiophene (PDPP-TT) and elastomeric poly(dimethylsiloxane) (PDMS)—in a single triblock copolymer (TBC) chain is reported, which enables high charge carrier mobility and low modulus in one system. Three TBCs containing up to 65 wt% PDMS were obtained, and the TBC with 65 wt% PDMS content exhibits mobilities up to 0.1 cm2 V−1 s−1, in the range of the fully conjugated reference polymer PDPP-TT (0.7 cm2 V−1 s−1). The TBC is ultrasoft with a low elastic modulus (5 MPa) in the range of mammalian tissue. The TBC exhibits an excellent stretchability and extraordinary durability, fully maintaining the initial electric conductivity in a doped state after 1500 cycles to 50% strain. © 2020 The Authors. Advanced Materials published by Wiley-VCH GmbH
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    Freestanding Nanolayers of a Wide-Gap Topological Insulator through Liquid-Phase Exfoliation
    (Weinheim : Wiley-VCH, 2021) Lê Anh, Mai; Potapov, Pavel; Wolf, Daniel; Lubk, Axel; Glatz, Bernhard; Fery, Andreas; Doert, Thomas; Ruck, Michael
    The layered salt Bi14Rh3I9 is a weak three-dimensional (3D) topological insulator (TI), that is, a stack of two-dimensional (2D) TIs. It has a wide non-trivial band gap of 210 meV, which is generated by strong spin-orbit coupling, and possesses protected electronic edge-states. In the structure, charged layers of (Formula presented.) (Bi4Rh)3I]2+ honeycombs and (Formula presented.) Bi2I8]2− chains alternate. The non-trivial topology of Bi14Rh3I9 is an inherent property of the 2D intermetallic fragment. Here, the exfoliation of Bi14Rh3I9 was performed using two different chemical approaches: (a) through a reaction with n-butyllithium and poly(vinylpyrrolidone), (b) through a reaction with betaine in dimethylformamide at 55 °C. The former yielded few-layer sheets of the new compound Bi12Rh3I, while the latter led to crystalline sheets of Bi14Rh3I9 with a thickness down to 5 nm and edge-lengths up to several ten microns. X-ray diffraction and electron microscopy proved that the structure of Bi14Rh3I9 remained intact. Thus, it was assumed that the particles are still TIs. Dispersions of these flakes now allow for next steps towards the envisioned applications in nanoelectronics, such as the study of quantum coherence in deposited films, the combination with superconducting particles or films for the generation of Majorana fermions, or studies on their behavior under the influence of magnetic or electric fields or in contact with various materials occurring in devices. The method presented generally allows to exfoliate layers with high specific charges and thus the use of layered starting materials beyond van der Waals crystals. © 2020 The Authors. Chemistry - A European Journal published by Wiley-VCH GmbH