Chemical Doping of Conjugated Polymers with the Strong Oxidant Magic Blue
Anna Hofmann, Renee Kroon, Sepideh Zokaei, Emmy Järsvall, Claudia Malacrida, Sabine Ludwigs, Till Biskup, Christian Müller
Abstract
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 × 10 3 m 2 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 10 26 m −3 , which yields a charge‐carrier mobility of up to 0.5 cm 2 V −1 s −1 for the most heavily doped material.