Controlled n-Doping of Naphthalene Diimide-Based Two-Dimensional Polymers

Austin Evans, Kelsey Collins, Sangni Xun, Taylor Allen, Samik Jhulki, Ioannina Castano, Hannah Smith, Michael Strauss, Alexander Oanta, Lujia Liu, Lei Sun, Obadiah Reid, Gjergji Sini, Danilo Puggioni, James Rondinelli, Tijana Rajh, Nathan Gianneschi, Antoine Kahn, Danna Freedman, Hong LiStephen Barlow, Garry Rumbles, Jean-Luc Bredas, Seth Marder, William Dichtel

Research output: Contribution to journalArticlepeer-review

16 Scopus Citations

Abstract

2D polymers (2DPs) are promising as structurally well-defined, permanently porous, organic semiconductors. However, 2DPs are nearly always isolated as closed shell organic species with limited charge carriers, which leads to low bulk conductivities. Here, the bulk conductivity of two naphthalene diimide (NDI)-containing 2DP semiconductors is enhanced by controllably n-doping the NDI units using cobaltocene (CoCp2). Optical and transient microwave spectroscopy reveal that both as-prepared NDI-containing 2DPs are semiconducting with sub-2 eV optical bandgaps and photoexcited charge-carrier lifetimes of tens of nanoseconds. Following reduction with CoCp2, both 2DPs largely retain their periodic structures and exhibit optical and electron-spin resonance spectroscopic features consistent with the presence of NDI-radical anions. While the native NDI-based 2DPs are electronically insulating, maximum bulk conductivities of >10−4S cm−1 are achieved by substoichiometric levels of n-doping. Density functional theory calculations show that the strongest electronic couplings in these 2DPs exist in the out-of-plane (π-stacking) crystallographic directions, which indicates that cross-plane electronic transport through NDI stacks is primarily responsible for the observed electronic conductivity. Taken together, the controlled molecular doping is a useful approach to access structurally well-defined, paramagnetic, 2DP n-type semiconductors with measurable bulk electronic conductivities of interest for electronic or spintronic devices.

Original languageAmerican English
Article number2101932
Number of pages9
JournalAdvanced Materials
Volume34
Issue number22
DOIs
StatePublished - 2022

Bibliographical note

Publisher Copyright:
© 2022 Wiley-VCH GmbH.

NREL Publication Number

  • NREL/JA-5900-79759

Keywords

  • 2D polymers
  • conductive polymers
  • n-type molecular doping
  • organic semiconductors

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