Modification of the Poly(bisdodecylquaterthiophene) Structure for High and Predominantly Nonionic Conductivity with Matched Dopants

Abstract

Four p-type polymers were synthesized by modifying poly(bisdodecylquaterthiophene) (PQT12) to increase oxidizability by p-dopants. A sulfur atom is inserted between the thiophene rings and dodecyl chains, and/or 3,4-ethylenedioxy groups are appended to thiophene rings of PQT12. Doped with NOBF4, PQTS12 (with sulfur in side chains) shows a conductivity of 350 S cm, the highest reported nonionic conductivity among films made from dopant-polymer solutions. Doped with tetrafluorotetracyanoquinodimethane (F4TCNQ), PDTDE12 (with 3,4-ethylenedioxy groups on thiophene rings) shows a conductivity of 140 S cm. The converse combinations of polymer and dopant and formulations using a polymer with both the sulfur and ethylenedioxy modifications showed lower conductivities. The conductivities are stable in air without extrinsic ion contributions associated with PEDOT:PSS that cannot support sustained current or thermoelectric voltage. Efficient charge transfer, tighter π-π stacking, and strong intermolecular coupling are responsible for the conductivity. Values of nontransient Seebeck coefficient and conductivity agree with empirical modeling for materials with these levels of pure hole conductivity; the power factor compares favorably with prior p-type polymers made by the alternative process of immersion of polymer films into dopant solutions. Models and conductivities point to significant mobility increases induced by dopants on the order of 1-5 cm V s, supported by field-effect transistor studies of slightly doped samples. The thermal conductivities were in the range of 0.2-0.5 W m K, typical for conductive polymers. The results point to further enhancements that could be obtained by increasing doped polymer mobilities.

Bringing Conducting Polymers to High Order: Toward Conductivities beyond 105 S cm−1 and Thermoelectric Power Factors of 2 mW m−1 K−2

“…[4] However, it is worth noting that it is necessary to realize a progressive doping with increasing dopant concentration to reach such large conductivities. [42] This value is larger than the (0.3-0.95) × 10 20 cm −3 reported for FTS-doped PBTTT. As a matter of fact, PBTTTs with shorter or longer alkyl side chains showed also very high conductivities (see Table S1 in the Supporting Information) albeit below those of C 12 -PBTTT.…”

Conductive, Solution‐Processed Dioxythiophene Copolymers for Thermoelectric and Transparent Electrode Applications

“…As listed in Table 1, the electrical conductivity of the P x E y series show that, like the previously mentioned electrochemical capacitance, there is a trend based on the EDOT content in the repeat unit. This is expected as soluble dioxythiophene based polymers are typically disordered [10,24,25] and other properties of these materials (e.g., λ max or electrochromic contrast) do not show molecular weight dependencies above a certain point, which is unique for each polymer (≈9 kDa as measured by GPC versus polystyrene for PProDOT). There is no apparent trend between the GPC estimated molecular weights (listed in Table S2 of the Supporting Information) and electrical conductivity of the polymers, suggesting that the difference in conductivity is primarily controlled by the repeat unit structure (e.g., relative number of side chains or electron richness of the repeat unit), local polymer structure, anion structure, and redox doping level, as opposed to the ultimate chain length.…”

“…[39] Using blade coating as the optimized casting method for PE 2 , various dopants were then tested (via solution doping for the same time period) and the thermoelectric properties were compared, as shown in Figure 2. [9,10,13,15] Once AgPF 6 was chosen as the best of this set of dopants for generating high conductivity PE 2 films, the final optimization was to vary the doping level by changing the dopant concentration and doping time. Iron(III) and Ag(I) based dopants were then investigated due to their relatively low cost, commercial availability, and previous use in doping conjugated polymer films to achieve high σ values.…”

“…[5,6] Recently, conductivity values of ≈10-350 S cm −1 have been reported [7][8][9][10][11][12] for charge neutral conjugated polymers (soluble in organic solvents) with film microstructures that favor high charge carrier mobilities that were subsequently oxidatively doped in solution to yield films with long range order. [5,6] Recently, conductivity values of ≈10-350 S cm −1 have been reported [7][8][9][10][11][12] for charge neutral conjugated polymers (soluble in organic solvents) with film microstructures that favor high charge carrier mobilities that were subsequently oxidatively doped in solution to yield films with long range order.…”

“…[5,6] Recently, conductivity values of ≈10-350 S cm −1 have been reported [7][8][9][10][11][12] for charge neutral conjugated polymers (soluble in organic solvents) with film microstructures that favor high charge carrier mobilities that were subsequently oxidatively doped in solution to yield films with long range order. [16,17] More readily doped materials including a glycolated polythiophene [15] and an alkylated bithiophene-alt-biEDOT polymer [10] (both doped with F 4 TCNQ) were reported with σ values of 100 and 140 S cm −1 , respectively. [9,11,[13][14][15] Beyond this, the crystalline domains in the many of these materials complicate doping.…”