|Schmode, P.; Hochgesang, A.; Goel, M.; Meichsner, F.; Mohanraj, J.; Fried, M.; Thelakkat, M.: A Solution-Processable Pristine PEDOT Exhibiting Excellent Conductivity, Charge Carrier Mobility, and Thermal Stability in the Doped State, Macromolecular Chemistry and Physics, 2100123 (2021) -- DOI: doi.org/10.1002/macp.202100123|
PEDOT:PSS [poly(3,4-ethylenedioxythiophene) polystyrene sulfonate] is a widely used insoluble conducting polymer, which is therefore processed from dispersions. In this work, PEDOT homopolymers (PEDOT-C6C8 1 and 2) highly soluble in common solvents like toluene, tetrahydrofuran, and chloroform are synthesized with a high control of molecular weight and low dispersity using Kumada catalyst transfer polymerization of a newly synthesized EDOT monomer carrying a branched alkyl substituent. Pristine PEDOT-C6C8 allows the use in accumulation mode transistors with a high charge carrier mobility of 5 × 10−4 cm2 V−1 s−1. Moreover, these polymers can be doped in a controlled fashion, reaching conductivities of 10−3 S cm−1 at 10 mol% of a dopant, Spiro-MeOTAD(TFSI)2. The doped state is remarkably stable, retaining 80% of the initial value after annealing under nitrogen at 100 °C and being exposed to ambient atmosphere for up to 12 h. During doping, the hole injection barrier decreases and reaches an impressively low value of 130 meV at only 2.5 mol% dopant loading without loss in carrier mobility; as monitored using ultraviolet photoelectron- and impedance spectroscopy. This new design concept leading to highly soluble polymers with well-controlled molecular weights provides solution-processable PEDOT dopable in a well-controlled fashion.