the doping of organic semiconductors to improve device performance is an important topic in organic electronics. Recently, we reported a new powerful p-dopant hexacyano-trimethylene-cyclopropane, CN6-CP [1]. Interestingly, its single electron reduction product CN6-CP•- has a high enough doping strength (the second reduction peak of CN6-CP peaks is at -5.1 eV) which is comparable with the strength of the state-of-the-art F4TCNQ [2]. Herein we demonstrate that highly efficient 2D (interfacial) doping of organic semiconductors, poly(3-hexylthiophene) (P3HT) and TIPS-pentacene, can be achieved by a polyelectrolyte-supported layer-by-layer assembly of the dual-mode functional dopant CN6-CP^•-K⁺, having an anionic group for its fixation onto oppositely charged surfaces/molecules as well as electron-deficient groups providing its p-doping ability [Kiriy et al., under review]. Polyelectrolyte-supported dopant layers were used to generate conductive channels at the bottom or at the top of semiconducting films. Unlike to the case of sequentially processed P3HT films doped by F4TCNQ, the use of more polar CN6-CP^•-K⁺ dopant and ultra-thin polycation separation interlayer enables predominantly interfacial kind of doping placement with no detectable intercalation of the dopant into the semiconductor bulk. The layered structure of the doped film was proved by transmission electron microscopy of the cross-section and it agrees well with other data obtained in this work. The interfacial doping enabled an impressive conductivity of 13 S/cm even for ultra-thin P3HT films. We propose to explain the superior efficiency of the interfacial doping compared to the bulk doping in terms of unperturbed morphology of the semiconductor and high mobility of charge carriers, which are spatially-separated from the dopant phase.

[1] Karpov, Y.; Erdmann, T.; Raguzin, I., Al-Hussein, M.; Binner, M.; Lappan, U.; Stamm, M.; Gerasimov, K. L.; Beryozkina, T.; Bakulev, V.; Anokhin, D. V.; Ivanov, D. A.; Günther, F.; Gemming, S.; Seifert, G.; Voit, B.; Di Pietro, R.; Kiriy, A. High Conductivity in Molecularly p‐Doped Diketopyrrolopyrrole‐Based Polymer: The Impact of a High Dopant Strength and Good Structural Order. Adv. Mater. 2016, 28, 6003-6010.

[2] Karpov, Y.; Kiriy, N.; Al-Hussein, M.; Hambsch, M.; Beryozkina, T.; Bakulev, V.; Mannsfeld, S. C. B.; Voit, B.; Kiriy, A. Hexacyano-[3]-radialene Anion-radical Salts: A Promising Family of Highly Soluble p-Dopants. Chem. Commun. 2018, 54, 307-310.