Impact of Cation Insertion on Semiconducting Polymer Thin Films toward Electrochemical Energy Conversion

Li, Shuya [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000153208452); Thurston, Jonathan R. [Univ. of Colorado, Boulder, CO (United States)] (ORCID:0000000312758823); Kopcha, William P. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000188111669); Brown, Megan R. [Univ. of Kentucky, Lexington, KY (United States)]; Bombile, Joel H. [Univ. of Kentucky, Lexington, KY (United States)] (ORCID:0000000191601343); Suo, Sa [Emory Univ., Atlanta, GA (United States)] (ORCID:0000000300168463); Dong, Bo [Emory Univ., Atlanta, GA (United States)]; Wright, Demelza [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000288542714); Gish, Melissa K. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000298863626); McCulloch, Iain [Princeton Univ., NJ (United States)]; Risko, Chad [Univ. of Kentucky, Lexington, KY (United States)] (ORCID:0000000198385233); Lian, Tianquan [Emory Univ., Atlanta, GA (United States)] (ORCID:0000000283513690); Toney, Michael F. [Univ. of Colorado, Boulder, CO (United States)] (ORCID:0000000275131166); Reid, Obadiah G. [National Laboratory of the Rockies (NLR), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States). Renewable and Sustainable Energy Institute (RSEI)] (ORCID:0000000306463981); Ferguson, Andrew J. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000325441753); Miller, Elisa M. [National Laboratory of the Rockies (NLR), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States). Renewable and Sustainable Energy Institute (RSEI)] (ORCID:0000000276485433); Greenaway, Ann L. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000166819965)

doi:10.1021/acs.chemmater.5c01779

DOE OSTI · 3015393

Impact of Cation Insertion on Semiconducting Polymer Thin Films toward Electrochemical Energy Conversion

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Abstract

Semiconducting polymers are being explored for electrochemical and photoelectrochemical energy transformation and storage applications. For these applications, it is critical to understand how ion insertion from the electrolyte into polymer electrodes modulates the polymer electronic structure and electron doping levels. Here, this study explores electrochemical cation insertion in the n-type conjugated redox polymer P90, composed of alternating naphthalene diimide (NDI) acceptor and bithiophene (T2) donor units, where the NDI units are functionalized with heptaethylene glycol (HEG, 90%) and 2-octyl dodecyl (OD, 10%) side chains. By combining in situ techniques (UV-vis absorption and Raman spectroscopies with electrochemistry), structural analysis using ex situ grazing-incidence wide-angle X-ray scattering (GIWAXS), and density functional theory (DFT) calculations, we reveal that dications enable negative polaron and bipolaron formation in the P90 at less reducing potentials while supporting more bipolaron formation than the monocations; moreover, larger dications with smaller hydrated radii increase the maximum P90 electron doping level. We also determine that the monocations lead to more thermodynamically stabilized polarons compared with the dications. These findings highlight the critical role of cation identity in tuning electrochemical charging, charge stabilization, and electronic structure of n-type conjugated redox polymers, providing guidance on the rational design of polymer-based (photo)electrochemical applications.

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37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY electron localization ion insertion operando characterization photoelectrochemical energy conversion size effect

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Li, Shuya [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000153208452), Thurston, Jonathan R. [Univ. of Colorado, Boulder, CO (United States)] (ORCID:0000000312758823), Kopcha, William P. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000188111669), Brown, Megan R. [Univ. of Kentucky, Lexington, KY (United States)], Bombile, Joel H. [Univ. of Kentucky, Lexington, KY (United States)] (ORCID:0000000191601343), Suo, Sa [Emory Univ., Atlanta, GA (United States)] (ORCID:0000000300168463), Dong, Bo [Emory Univ., Atlanta, GA (United States)], Wright, Demelza [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000288542714), Gish, Melissa K. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000298863626), McCulloch, Iain [Princeton Univ., NJ (United States)], Risko, Chad [Univ. of Kentucky, Lexington, KY (United States)] (ORCID:0000000198385233), Lian, Tianquan [Emory Univ., Atlanta, GA (United States)] (ORCID:0000000283513690), Toney, Michael F. [Univ. of Colorado, Boulder, CO (United States)] (ORCID:0000000275131166), Reid, Obadiah G. [National Laboratory of the Rockies (NLR), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States). Renewable and Sustainable Energy Institute (RSEI)] (ORCID:0000000306463981), Ferguson, Andrew J. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000325441753), Miller, Elisa M. [National Laboratory of the Rockies (NLR), Golden, CO (United States); Univ. of Colorado, Boulder, CO (United States). Renewable and Sustainable Energy Institute (RSEI)] (ORCID:0000000276485433), Greenaway, Ann L. [National Laboratory of the Rockies (NLR), Golden, CO (United States)] (ORCID:0000000166819965). 2026-01-08. Impact of Cation Insertion on Semiconducting Polymer Thin Films toward Electrochemical Energy Conversion. https://doi.org/10.1021/acs.chemmater.5c01779

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