Diffusion of Brønsted acidic dopants in conjugated polymers

Abstract

An examination of the mechanism of electrical doping of films of poly(3-hexylthiophene) by a strong Brønsted acids reveals a heavily doped surface layer that limits diffusion of the acid into the bulk.

Tuning Transport via Interaction Strength in Cationic Conjugated Polyelectrolytes

“…For example, fuel cells require H + conduction, while batteries rely on metal cation conduction. Anion transport can also be of interest, where semiconducting applications typically focus on mixed conduction in the context of dopant counterion diffusion . For the next generation of mixed conducting polymers, structure–property relationships must be developed to enable predictable tunability of a range of transport properties for these highly tailored applications .…”

Interfacial doping of semiconducting polymers with phenothiazine-based polymeric ionic liquids

“…Previously, study showed that TFSI − counterion has very restricted diffusion above the observed doping depth even with prolonged thermal annealing at elevated temperature. 18 This could be ascribed to the increased modulus and shift in T g observed for doped conjugated polymers, and thus limiting the mobility of the counterions from the doped surfaces. 48,49…”

“…Recently, our group has reported the kinetics of doping and diffusion of Brønsted acid doping from solution of P3HT using HTFSI. 18 The coupled P3HT + :TFSI À pairs showed a relatively slow diffusion coefficient of B1.0 nm 2 min À1 based on reaction-diffusion modeling. Although methanol was used as the solvent for the acid doping process, which swells P3HT differently than DCM, we can use the diffusion coefficient as a rough estimate here.…”

“…5,11 This method allows for control over the degree of doping by controlling the concentration of the dopant solutions. 6,17,18…”

“…5,11 This method allows for control over the degree of doping by controlling the concentration of the dopant solutions. 6,17,18 The sequential doping process is effective, but restricted by (i) limited dopant choices, (ii) uncertainties on the dopant penetration depth, (iii) difficulty in precise control over doping levels, and (iv) requirement for orthogonal solvents. In particular, the choice of the dopants is limited to strong dopants such as F 4 TCNQ (electron affinity, EA = 5.2 eV), tris(4-bromophenyl)ammoniumyl hexachloroantimonate (Magic Blue, EA of radical cation form = 5.8 eV), or NOPF 6 (EA of NO + = 6.5 eV) (Table S1, ESI †); note that for the radical cations we define the EA based on their reduction potential to their neutral form referenced to the vacuum level.…”