Room-temperature bandlike transport and Hall effect in a high-mobility ambipolar polymer

Abstract

The advent of a new class of high-mobility semiconducting polymers opens up a window to address fundamental issues in electrical transport mechanism such as transport between localized states versus extended state conduction. Here, we investigate the origin of the ultralow degree of disorder $({E}_{a}\ensuremath{\sim}16\phantom{\rule{0.16em}{0ex}}\mathrm{meV})$ and the ``bandlike'' negative temperature ($T$) coefficient of the field effect electron mobility: ${\ensuremath{\mu}}_{\mathrm{FET}}^{e}(T)$ in a high performance $({\ensuremath{\mu}}_{\mathrm{FET}}^{e}>2.5\phantom{\rule{0.16em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}\phantom{\rule{0.28em}{0ex}}{\mathrm{V}}^{\ensuremath{-}1}\phantom{\rule{0.16em}{0ex}}{\mathrm{s}}^{\ensuremath{-}1})$ diketopyrrolopyrrole based semiconducting polymer. Models based on the framework of mobility edge with exponential density of states are invoked to explain the trends in transport. The temperature window over which the system demonstrates delocalized transport was tuned by a systematic introduction of disorder at the transport interface. Additionally, the Hall mobility $({\ensuremath{\mu}}_{\mathrm{Hall}}^{e})$ extracted from Hall voltage measurements in these devices was found to be comparable to field effect mobility $({\ensuremath{\mu}}_{\mathrm{FET}}^{e})$ in the high $T$ bandlike regime. Comprehensive studies with different combinations of dielectrics and semiconductors demonstrate the effectiveness of rationale molecular design, which emphasizes uniform-energetic landscape and low reorganization energy.