A Solution‐Doped Polymer Semiconductor:Insulator Blend for Thermoelectrics

Abstract

Poly(ethylene oxide) is demonstrated to be a suitable matrix polymer for the solution‐doped conjugated polymer poly(3‐hexylthiophene). The polarity of the insulator combined with carefully chosen processing conditions permits the fabrication of tens of micrometer‐thick films that feature a fine distribution of the F4TCNQ dopant:semiconductor complex. Changes in electrical conductivity from 0.1 to 0.3 S cm−1 and Seebeck coefficient from 100 to 60 μV K−1 upon addition of the insulator correlate with an increase in doping efficiency from 20% to 40% for heavily doped ternary blends. An invariant bulk thermal conductivity of about 0.3 W m−1 K−1 gives rise to a thermoelectric Figure of merit ZT ∼ 10−4 that remains unaltered for an insulator content of more than 60 wt%. Free‐standing, mechanically robust tapes illustrate the versatility of the developed dopant:semiconductor:insulator ternary blends.

Self‐Healable and Stretchable Organic Thermoelectric Materials: Electrically Percolated Polymer Nanowires Embedded in Thermoplastic Elastomer Matrix

“…The ε value was calculated from the equation ε = ( L e − L 0 )/ L 0 × 100%, where L e is the elongated length and L 0 is the initial length. Although both the R s / R 0 value and the S / S 0 value increased with increasing ε, their variations were found to be much smaller than those for previously reported stretchable TE materials; R s / R 0 and S / S 0 reached 4.6 and 1.7, respectively, at ε of 100% . The increases in R s and S upon stretching might have been caused by the occurrence of small cracks that could affect the charge transport and phonon drag .…”

“…As a result, the samples with ϕ BCF of 27 mol% showed improved PF values, with a maximum PF value of 1.16 µW m −1 K −2 (Figure a). This value was found to be about one order of magnitude higher than those of recently reported stretchable organic TE materials . As shown in Figure a, the PF value of the sample with ϕ BCF of 27 mol% also showed an increasing trend with increasing ω P3BT .…”

“…Therefore, the low thermal conductivity can be a comparative advantage for using P3BT nanowires instead of 1D inorganic nanomaterials such as silver nanowires or carbon nanotubes that typically show much higher thermal conductivities . In addition, the ZT value of our samples was about one order of magnitude higher than that of recently reported stretchable organic TE materials …”

“…Recently, a few studies have reported the enhanced flexibility and stretchability of organic TE materials . For example, Kiefer et al introduced a stretchable polymer semiconductor/insulator blend, which nevertheless showed two‐order‐of‐magnitude increased resistances at 100% strain . Jo et al introduced a fluorosurfactant into conducting polymers to control the stretchability and achieved stable TE performance until 60% strain .…”

Influence of crystallinity on the thermoelectric power factor of P3HT vapour-doped with F4TCNQ

“…4). 6,11,17,[28][29][30][31][32][33][34][35][36][37] The variation in Seebeck coefficient with electrical conductivity follows the empirical trend described by eqn (2) (Fig. 4, top).…”