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Atomic-Level Insight into the Postsynthesis Band Gap Engineering of a Lewis Base Polymer Using Lewis Acid Tris(pentafluorophenyl)borane

Journal Article · · Chemistry of Materials

Here, we investigate the binding properties of the Lewis acid tris(pentafluorophenyl)borane with a Lewis base semiconducting polymer, PFPT, and the subsequent mechanism of band gap reduction. Experiments and quantum chemical calculations confirm that the formation of a Lewis acid adduct is energetically favorable (ΔG° < -0.2 eV), with preferential binding at the pyridyl nitrogen in the polymer backbone over other Lewis base sites. Upon adduct formation, ultraviolet photoelectron spectroscopy indicates only a slight decrease in the HOMO energy, implying that a larger reduction in the LUMO energy is primarily responsible for the observed optical band gap narrowing (ΔEopt = 0.3 eV). Herein, we also provide the first spatially resolved picture of how Lewis acid adducts form in heterogeneous, disordered polymer/tris(pentafluorophenyl)borane thin films via one- (1D) and two-dimensional (2D) solid-state nuclear magnetic resonance. Notably, solid-state 1D 11B, 13C{1H}, and 13C{19F} cross-polarization magic-angle spinning (CP-MAS) NMR and 2D 1H{19F} and 1H{1H} correlation NMR analyses establish that BCF molecules are intercalated between branched C16H33 side chains with the boron atom facing toward the pyridyl nitrogen atoms of PFPT.

Research Organization:
Univ. of California, Santa Barbara, CA (United States); Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA (United States). Advanced Light Source (ALS)
Sponsoring Organization:
USDOE Office of Science (SC), Basic Energy Sciences (BES); Alexander von Humboldt Foundation; Bavaria California Technology Centre (BaCaTec); National Science Foundation (NSF); Mitsubishi Chemical-Centre for Advanced Materials
Grant/Contract Number:
SC0017659; AC02-05CH11231
OSTI ID:
1593943
Alternate ID(s):
OSTI ID: 1661629
Journal Information:
Chemistry of Materials, Journal Name: Chemistry of Materials Journal Issue: 17 Vol. 31; ISSN 0897-4756
Publisher:
American Chemical Society (ACS)Copyright Statement
Country of Publication:
United States
Language:
English

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