Switching a polymer Electrically switchable metasurfaces and plasmonic materials will enable the development of active nanophotonic technology. Karst et al . show that a metallic polymer can be used for electrical switching of plasmonic nanoantenna resonances. The plasmonic resonance can be completely switched ON and OFF with switching speeds up to 30 hertz (video rate), low switching voltages of ±1 volt (complementary metal-oxide semiconductor compatible), and a switching contrast of 100%. The results could have applications in nanophotonic devices such as those used in augmented and virtual reality imaging applications. —ISO

In this work, we demonstrate that high solid-state conductivities of simply spin-coated poly­(3-hexylthiophene) (P3HT) films can be obtained by means of an ex situ electrochemical doping strategy using 4-line electrodes. With increasing electrochemical doping potential, we find an increase in conductivity over 6 orders of magnitude, giving a maximum conductivity up to 224 S cm–1 with maximum hole densities of 1021 holes per cm3. Most intriguingly, highly conducting states are achieved over a very broad potential range from 0.4 to 0.8 V versus Fc/Fc+ in the doped state. The experiments are complemented by UV–vis–NIR absorption and electron paramagnetic resonance spectroscopy in the solid state as well as with in situ electrochemical measurements which confirm that the electrochemically generated doped species can be successfully transferred into the solid state. Our results suggest that for reaching high conducting states, P3HT has to be present in different redox states and that the plateau conductivity region should arise from the coexistence of overlapping polaron and bipolaron states. Comparisons to films of regiorandom P3HT and pure redox polymer systems based on diphenyl-3,3′-bicarbazyl are further presented, which highlight the role of mixed valence states in conducting polymers. Last but not least, the highly conducting films are simply spin-coated and therefore rather disordered, adding new aspects to the discussion whether high crystallinity is a prerequisite for achieving high conductivities in conjugated polymers.

This review article gives an overview of past and current activities in the Linear Conjugated Systems Group of Angers and in the IPOC – Functional Polymers Group of the Institute of Polymer Chemistry of Stuttgart on the use of triphenylamine (TPA) as versatile building block for organic electronics. In the first part, the properties of TPA itself are introduced including geometrical and energy level considerations. Dimerization of TPA to tetraphenylbenzidine upon electrochemical oxidation is highlighted. The blocking of TPA para‐positions and its implications in terms of electroactivity is further discussed. The second part shows that dimerization of TPA as pendant redox‐active moieties in polymers is a versatile strategy to crosslink polymer films. Coming from redox homopolymers the crosslinking strategy is extended towards conjugated redox polymers based on polythiophenes and block copolymers. Conductivity mechanisms and the influence of doping level on conductivity are probed with cyclic voltammetry coupled with in situ conductance and four‐point probe measurements. The last part is dedicated to the use of TPA as an electron‐donating block in the design of donor‐π‐acceptor chromophores and their use as active material in organic photovoltaics. An overview of some relevant TPA‐based push–pull molecules from the literature and our contribution to this field is presented emphasizing the progress of the photovoltaic performance of organic solar cells made over the last decade. © 2018 Society of Chemical Industry

The opto-electronic as well as the mechanical properties of semiconducting polymers depend strongly on the charge-carrier density, which can be tuned chemically or electrochemically, a process which is referred to as doping. Hence, doping is a powerful tool to optimize the performance of organic electronic devices, such as transistors, solar cells and organic light-emitting diodes (OLEDs), [1,5] as well as of organic thermoelectric materials. [6][7][8] Further, in case of electrochemical transistors and light-emitting electrochemical cells, modulation of the charge-carrier density is essential to the operation of these devices. [9,10] One way to introduce charges is via redox doping, also referred to as molecular doping, which involves an electron transfer between the semiconducting polymer and a small molecule, the socalled redox dopant. In case of p-doping a positive energetic offset between the electron affinity (EA) of the small-molecular dopant and the ionization energy (IE) of the semiconducting polymer is advantageous, i.e., EA dopant > IE polymer . Depending on the relative position of the energy levels one or even two electrons can be transferred from the polymer backbone to a dopant molecule. [11] A broad variety of p-and n-type polymer-dopant couples have been studied. The most common p-type redox dopant is 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane (F4TCNQ), [12,13] which shows an electron affinity of EA ≈ 5.2 eV and readily oxidizes polymers such as poly(3-hexylthiophene) (P3HT; IE ≈ 5.1 eV) [14][15][16][17][18][19] and thiophene-thienothiophene copolymers (PBTTT; IE ≈ 5.2 eV). [20,21] Many other conjugated polymers such as, for example, high-mobility donor-acceptor polymers have an IE of more than 5.3 eV and can therefore not be doped with F4TCNQ. At the same time, doping of high mobility polymers is of special interest in the field of organic thermoelectrics, because the use of such polymers may allow to increase the thermoelectric power factor, which scales with the electrical conductivity and hence charge-carrier mobility. [22,23] There are only few examples of dopants with a high electron affinity including 1,3,4,5,7,8-hexafluoro-tetracyano-naphthoquinodimethane (F6TCNNQ) (EA ≈ 5.3 eV), [11,24] hexacyano-trimethylene-cyclopropane (EA ≈ 5.9 eV) [24] and its derivatives, [25] and molybdenum dithiolene complexes such as Mo(tfd-COCF 3 ) 3 Molecular doping of organic semiconductors is a powerful tool for the optimization of organic electronic devices and organic thermoelectric materials. However, there are few redox dopants that have a sufficiently high electron affinity to allow the doping of conjugated polymers with an ionization energy of more than 5.3 eV. Here, p-doping of a broad palette of conjugated polymers with high ionization energies is achieved by using the strong oxidant tris(4bromophenyl)ammoniumyl hexachloroantimonate (Magic Blue). In particular diketopyrrolopyrrole (DPP)-based copolymers reach a conductivity of up to 100 S cm −1 and a thermoelectric power factor of 10 µW m −...