Double doping of conjugated polymers with monomer molecular dopants

David Kiefer, Renee Kroon, Anna I. Hofmann, Hengda Sun, Xianjie Liu, Alexander Giovannitti, Dominik Stegerer, Alexander Cano, Jonna Hynynen, Liyang Yu, Yadong Zhang, Dingqi Nai, Thomas F. Harrelson, Michael Sommer, Adam J. Moulé, Martijn Kemerink, Seth R. Marder, Iain McCulloch, Mats Fahlman, Simone FabianoChristian Müller

Research output: Contribution to journalArticlepeer-review

104 Scopus citations

Abstract

Molecular doping is a crucial tool for controlling the charge-carrier concentration in organic semiconductors. Each dopant molecule is commonly thought to give rise to only one polaron, leading to a maximum of one donor:acceptor charge-transfer complex and hence an ionization efficiency of 100%. However, this theoretical limit is rarely achieved because of incomplete charge transfer and the presence of unreacted dopant. Here, we establish that common p-dopants can in fact accept two electrons per molecule from conjugated polymers with a low ionization energy. Each dopant molecule participates in two charge-transfer events, leading to the formation of dopant dianions and an ionization efficiency of up to 200%. Furthermore, we show that the resulting integer charge-transfer complex can dissociate with an efficiency of up to 170%. The concept of double doping introduced here may allow the dopant fraction required to optimize charge conduction to be halved.
Original languageEnglish (US)
Pages (from-to)149-155
Number of pages7
JournalNature Materials
Volume18
Issue number2
DOIs
StatePublished - Jan 3 2019

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