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 −...

To realize thermoelectric textiles that can convert body heat to electricity, fibers with excellent mechanical and thermoelectric properties are needed. Although poly(3,4‐ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is among the most promising organic thermoelectric materials, reports that explore its use for thermoelectric fibers are all but absent. Herein, the mechanical and thermoelectric properties of wet‐spun PEDOT:PSS fibers are reported, and their use in energy‐harvesting textiles is discussed. Wet‐spinning into sulfuric acid results in water‐stable semicrystalline fibers with a Young's modulus of up to 1.9 GPa, an electrical conductivity of 830 S cm−1, and a thermoelectric power factor of 30 μV m−1 K−2. Stretching beyond the yield point as well as repeated tensile deformation and bending leave the electrical properties of these fibers almost unaffected. The mechanical robustness/durability and excellent underwater stability of semicrystalline PEDOT:PSS fibers, combined with a promising thermoelectric performance, opens up their use in practical energy‐harvesting textiles, as illustrated by an embroidered thermoelectric fabric module.

Molecular doping of a polythiophene with oligoethylene glycol side chains is found to strongly modulate not only the electrical but also the mechanical properties of the polymer.

Polar polythiophenes with oligoethylene glycol side chains are exceedingly soft materials. A low glass transition temperature and low degree of crystallinity prevents their use as a bulk material. The synthesis of a copolymer comprising 1) soft polythiophene blocks with tetraethylene glycol side chains, and 2) hard urethane segments is reported. The molecular design is contrary to that of other semiconductor‐insulator copolymers, which typically combine a soft nonconjugated spacer with hard conjugated segments. Copolymerization of polar polythiophenes and urethane segments results in a ductile material that can be used as a free‐standing solid. The copolymer displays a storage modulus of 25 MPa at room temperature, elongation at break of 95%, and a reduced degree of swelling due to hydrogen bonding. Both chemical doping and electrochemical oxidation reveal that the introduction of urethane segments does not unduly reduce the hole charge‐carrier mobility and ability to take up charge. Further, stable operation is observed when the copolymer is used as the active layer of organic electrochemical transistors.

The interplay between the nanostructure of a doped polythiophene with oligoether side chains and its electrical as well as mechanical properties is investigated.