Bandlike Transport in Ferroelectric-Based Organic Field-Effect Transistors

Abstract

Despite much study of the general mechanism of transport in organic transistors, their $p\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}l\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}r\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}z\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}n-d\phantom{\rule{0}{0ex}}o\phantom{\rule{0}{0ex}}m\phantom{\rule{0}{0ex}}i\phantom{\rule{0}{0ex}}n\phantom{\rule{0}{0ex}}a\phantom{\rule{0}{0ex}}t\phantom{\rule{0}{0ex}}e\phantom{\rule{0}{0ex}}d$ transport is still not well understood. Using a ferroelectric polymer for the dielectric layer in an organic field-effect transistor (OFET) allows tuning of polarization strength with temperature. Remarkably, at 200 K TIPS-pentacene OFETs with a ferroelectric dielectric exhibit a negative coefficient of mobility (bandlike transport, reminiscent of a metal, instead of the usual activated transport). The key to this behavior is the discrete nature of the trapping levels in TIPS-pentacene, and presumably other solution-processable $\ensuremath{\pi}$-conjugated conductors.