Chemical Doping of Conjugated Polymers with the Strong Oxidant Magic Blue

Abstract 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(4‐bromophenyl)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−1 K−2. Further, both electron paramagnetic resonance (EPR) as well as a combination of spectroelectrochemistry and chronoamperometry is used to estimate the charge‐carrier density of the polymer PDPP‐3T doped with Magic Blue. A molar attenuation coefficient of 6.0 ± 0.2 × 103 m2 mol−1 is obtained for the first polaronic sub‐bandgap absorption of electrochemically oxidized PDPP‐3T. Comparison with chemically doped PDPP‐3T suggests a charge‐carrier density on the order of 1026 m−3, which yields a charge‐carrier mobility of up to 0.5 cm2 V−1 s−1 for the most heavily doped material.