High Conductivity and Electron‐Transfer Validation in an n‐Type Fluoride‐Anion‐Doped Polymer for Thermoelectrics in Air

Abstract

Air-stable and soluble tetrabutylammonium fluoride (TBAF) is demonstrated as an efficient n-type dopant for the conjugated polymer ClBDPPV. Electron transfer from F anions to the π-electron-deficient ClBDPPV through anion-π electronic interactions is strongly corroborated by the combined results of electron spin resonance, UV-vis-NIR, and ultraviolet photoelectron spectroscopy. Doping of ClBDPPV with 25 mol% TBAF boosts electrical conductivity to up to 0.62 S cm , among the highest conductivities that have been reported for solution-processed n-type conjugated polymers, with a thermoelectric power factor of 0.63 µW m K in air. Importantly, the Seebeck coefficient agrees with recently published correlations to conductivity. Moreover, the F -doped ClBDPPV shows significant air stability, maintaining the conductivity of over 0.1 S cm in a thick film after exposure to air for one week, to the best of our knowledge the first report of an air-stable solution-processable n-doped conductive polymer with this level of conductivity. The result shows that using solution-processable small-anion salts such as TBAF as an n-dopant of organic conjugated polymers possessing lower LUMO (lowest unoccupied molecular orbital), less than -4.2 eV) can open new opportunities toward high-performance air-stable solution-processable n-type thermoelectric (TE) conjugated polymers.

Anion-induced N-doping of naphthalenediimide polymer semiconductor in organic thin-film transistors

“…18,42 During the course of this work the use of TBAF to dope fullerene derivatives and some polymer systems has emerged. 29,43,44 In some cases it appears that nucleophilic addition of the fluoride anion to the fullerene/polymer initially occurs, followed by an electron transfer from the resulting adduct to a neutral polymer chain. 43,44 To probe the possibility of the above hypothesis, we investigated the n-doping of the benchmark NDI-derivatised polymer P(NDI2OD-T2) with the Lewis basic anion fluoride (in the format of tetrabutylammonium fluoride (TBAF)).…”

“…29,43,44 In some cases it appears that nucleophilic addition of the fluoride anion to the fullerene/polymer initially occurs, followed by an electron transfer from the resulting adduct to a neutral polymer chain. 43,44 To probe the possibility of the above hypothesis, we investigated the n-doping of the benchmark NDI-derivatised polymer P(NDI2OD-T2) with the Lewis basic anion fluoride (in the format of tetrabutylammonium fluoride (TBAF)). We demonstrated that with only a small amount of TBAF dopant, the doping effect was already significant, as determined by OTFT characterisation.…”

Rigid Coplanar Polymers for Stable n‐Type Polymer Thermoelectrics

“…[5] In addition, most n-type polymer thermo-electric materials showed inferior stability under ambient conditions,f urther limiting their applications. [6] Hence,t here is an emerging requirement to develop n-type polymer thermoelectrics with high conductivities and good air stability.…”

“…These performance values are among the highest in n-type conjugated polymers,a nd the stability is superior compared with previous works. [6] Tw om onomers,b is(isatin) and benzodifurandione,w ere synthesized according to the literature (Scheme 1). [15] Acidcatalyzed aldol polymerization was used to link the two monomers,a nd two polymers, LPPV-1 and LPPV-2,w ith different alkyl chain lengths were synthesized.…”

Flexible n-Type Tungsten Carbide/Polylactic Acid Thermoelectric Composites Fabricated by Additive Manufacturing

“…The electrical conductivity of all the composites decreases with increasing temperature from 150 to 375 K. For increasing WC content (WP5, WP10, and WP15), the electrical conductivity increased from 16.7 to 51.1 S/cm at~150 K, mainly because WC has a relatively high electrical conductivity. This conductivity is much higher than that of most reported n-type conducting polymers and corresponding composites, such as the conjugated polymer ClBDPPV combined with 25 mol % tetrabutylammonium fluoride (0.62 S/cm) [30], the a1-ethyl-3-methylimidazolium ethyl-sulfate-doped polyaniline (0.23 S/cm) [31], the poly[K X (Ni-ett)] blended with poly(vinylidene fluoride) (PVDF)/DMSO on paper (0.5 S/cm) [32]. However, this value is smaller than that of Ni nanowire/PVDF nanocomposites (4701 S/cm), due to the much higher electrical conductivity of Ni nanowires (2.98 × 10 4 S/cm) [33].…”