Temperature dependent charge transport in electrostatically doped poly [benzimidazobenzophenanthroline] thin films

Charge transport in electrostatically doped poly[benzimidazobenzophenanthroline]-BBL thin films in a field-effect transistor geometry were investigated in the temperature range 150 K < T < 370 K. At low temperatures activation and hopping transport mechanisms dominated, while phonon scattering dominated at high temperatures. The activation energies (E-A) were found to lie in the range 140 meV < E-A < 400 meV implying the existence of deep traps within the polymer bandgap of 1.8 eV. Two quasi-linear dependencies of E-A on the gate voltage (V-g) were observed with E-A decreasing as V-g increased. An unexpected metallic-like transport characteristic appeared for T > 335 K which depended on V-g. Enhanced electron delocalization combined with increased carrier density could be responsible for this metallic-like behavior. Our results show that the existence of deep traps with multiple energy distributions, combined with increased carrier density led to the unusual temperature dependence of charge transport observed in BBL.

Automated summary

This study investigated charge transport in a field-effect transistor structure in a temperature range. At low temperatures, activation and hopping were dominant transport mechanisms, while phonon scattering dominated at high temperatures. The presence of deep traps within the polymer bandgap was observed, and the energy of the deep traps was dependent on the gate voltage. Furthermore, a metallic-like transport characteristic was observed at high temperatures, which could be attributed to enhanced electron delocalization and increased carrier density.