Metallic transport in polyaniline

Abstract

Despite nearly three decades of materials development, the transport properties in the 'metallic state' of the so-called conducting polymers are still not typical of conventional metals. The hallmark of metallic resistivity--a monotonic decrease in resistivity with temperature--has not been obtained at temperatures over the full range below room temperature; and a frequency dependent conductivity, sigma(omega), typical of metals has also not been observed. In contrast, the low-temperature behaviour of 'metallic' polymers has, in all previous cases, exhibited an increase in resistivity as temperature is further decreased, as a result of disorder-induced localization of the charge carriers. This disorder-induced localization also changes the infrared response such that sigma(omega) deviates from the prediction of Drude theory. Here we report classic metallic transport data obtained from truly metallic polymers. With polyaniline samples prepared using self-stabilized dispersion polymerization, we find that for samples having room-temperature conductivities in excess of 1,000 S cm(-1), the resistivity decreases monotonically as the temperature is lowered down to 5 K, and that the infrared spectra are characteristic of the conventional Drude model even at the lowest frequencies measured.

Hopping transport and the Hall effect near the insulator–metal transition in electrochemically gated poly(3-hexylthiophene) transistors

“…We thus searched for a Hall effect in the high p, high T region. Although the Hall effect has been reported sporadically in bulk semiconducting polymer samples on the metallic side of the insulator-metal transition 11,34 , its detection in thin film transistors and on the insulating side of the transition has traditionally been thwarted by low mobilities and high contact resistances. In our case, the mobility values are comparable to the best reported in P3HT thin film transistors (approaching 1 cm 2 V À 1 s À 1 ), and contact resistances are minimized by electrochemical doping 35 .…”

“…Elusive issues include the non-trivial influence of the multiple sources of disorder (for example, semi-crystallinity, paracrystallinity and nanoscale inhomogeneity [1][2][3][4][5][6][7], the elucidation of the important hopping mechanisms [1][2][3][4][7][8][9][10] , the effects of charge carrier-lattice interactions 3,4 and the identification of the ultimate limits on conductivity and mobility [1][2][3][4][5][6]11 . The latter is particularly important as, in addition to being of considerable fundamental interest the upper limits on conductivity and mobility also limit device performance (for example, transistor output current and operating frequency).…”

Transparent Conducting Polymer/Nitride Semiconductor Heterojunction Solar Cells

“…Among the various kinds of conducting polymers, we have focused primarily on polyaniline (PANI) and poly(ethylenedioxythiophene)-polystyrene sulfonate (PEDOT:PSS) because of their high conductivity (~1000  -1 cm -1 ) and high optical transparency (>80%) (Lee et al, 2006;Ha, 2004). Conducting polymers with high optical transparency are known as transparent conducting polymers (TCPs).…”

Use of x-ray scattering functions in Kramers-Kronig analysis of reflectance

“…Many reports of Kramers-Kronig analysis of reflectance have appeared, spanning more than 50 years, 7 with studies of metals, [8][9][10][11][12][13][14][15] pure and doped elemental solids, [16][17][18] organic conductors, [19][20][21] charge-density-wave materials, [22][23][24] conducting polymers, [25][26][27] cuprate superconductors, [28][29][30][31][32][33][34][35][36][37][38] manganites, [39][40][41] pnictides, [42][43][44][45][46][47][48] heavy-Fermions, 49 multiferroics, [50][51][52][53] topological insulators, [54][55][56] and many others. In addition, a number o...…”