Elementary steps in electrical doping of organic semiconductors

Max Tietze, Johannes Beduhn, Paul Pahner, Bernhard Nell, Martin Schwarze, Hans Kleemann, Markus Krammer, Karin Zojer, Koen Vandewal, Karl Leo

Research output: Contribution to journalArticle

Abstract


Fermi level control by doping is established since decades in inorganic semiconductors and has been successfully introduced in organic semiconductors. Despite its commercial success in the multi-billion OLED display business, molecular doping is little understood, with its elementary steps controversially discussed and mostly-empirical-materials design. Particularly puzzling is the efficient carrier release, despite a presumably large Coulomb barrier. Here we quantitatively investigate doping as a two-step process, involving single-electron transfer from donor to acceptor molecules and subsequent dissociation of the ground-state integer-charge transfer complex (ICTC). We show that carrier release by ICTC dissociation has an activation energy of only a few tens of meV, despite a Coulomb binding of several 100 meV. We resolve this discrepancy by taking energetic disorder into account. The overall doping process is explained by an extended semiconductor model in which occupation of ICTCs causes the classically known reserve regime at device-relevant doping concentrations
Original languageEnglish
Article number1182
JournalNature Communications
Volume9
DOIs
Publication statusPublished - 2018

Fields of Expertise

  • Advanced Materials Science

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