TY - JOUR
T1 - Thermally Induced Formation of HF4TCNQ-in F4TCNQ-Doped Regioregular P3HT
AU - Watts, Kristen E.
AU - Neelamraju, Bharati
AU - Moser, Maximilian
AU - McCulloch, Iain
AU - Ratcliff, Erin L.
AU - Pemberton, Jeanne E.
N1 - Publisher Copyright:
Copyright © 2020 American Chemical Society.
PY - 2020/8/20
Y1 - 2020/8/20
N2 - The prototypical system for understanding doping in solution-processed organic electronics has been poly(3-hexylthiophene) (P3HT) p-doped with 2,3,5,6-Tetrafluoro-7,7,8,8-Tetracyanoquinodimethane (F4TCNQ). Multiple charge-Transfer states, defined by the fraction of electron transfer to F4TCNQ, are known to coexist and are dependent on polymer molecular weight, crystallinity, and processing. Less well-understood is the loss of conductivity after thermal annealing of these materials. Specifically, in thermoelectrics, F4TCNQ-doped regioregular (rr) P3HT exhibits significant conductivity losses at temperatures lower than other thiophene-based polymers. Through detailed spectroscopic investigation of progressively heated P3HT films coprocessed with F4TCNQ, we demonstrate that this diminished conductivity is due to formation of the nonchromophoric, weak dopant HF4TCNQ-. This species is likely formed through hydrogen abstraction from the α aliphatic carbon of the hexyl chain at the 3-position of thiophene rings of rr-P3HT. This reaction is eliminated for polymers with ethylene glycol-containing side chains, which retain conductivity at higher operating temperatures. In total, these results provide a critical materials design guideline for organic electronics.
AB - The prototypical system for understanding doping in solution-processed organic electronics has been poly(3-hexylthiophene) (P3HT) p-doped with 2,3,5,6-Tetrafluoro-7,7,8,8-Tetracyanoquinodimethane (F4TCNQ). Multiple charge-Transfer states, defined by the fraction of electron transfer to F4TCNQ, are known to coexist and are dependent on polymer molecular weight, crystallinity, and processing. Less well-understood is the loss of conductivity after thermal annealing of these materials. Specifically, in thermoelectrics, F4TCNQ-doped regioregular (rr) P3HT exhibits significant conductivity losses at temperatures lower than other thiophene-based polymers. Through detailed spectroscopic investigation of progressively heated P3HT films coprocessed with F4TCNQ, we demonstrate that this diminished conductivity is due to formation of the nonchromophoric, weak dopant HF4TCNQ-. This species is likely formed through hydrogen abstraction from the α aliphatic carbon of the hexyl chain at the 3-position of thiophene rings of rr-P3HT. This reaction is eliminated for polymers with ethylene glycol-containing side chains, which retain conductivity at higher operating temperatures. In total, these results provide a critical materials design guideline for organic electronics.
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U2 - 10.1021/acs.jpclett.0c01673
DO - 10.1021/acs.jpclett.0c01673
M3 - Article
C2 - 32701299
AN - SCOPUS:85089768710
SN - 1948-7185
VL - 11
SP - 6586
EP - 6592
JO - Journal of Physical Chemistry Letters
JF - Journal of Physical Chemistry Letters
IS - 16
ER -