Electronic and ionic conduction in ligand-free lead selenide colloidal quantum dots

Abstract

We fabricated a ligand-free lead selenide (PbSe) colloidal quantum dot (CQD) film and probed its electrical properties using a field-effect transistor (FET) at low temperature. The contribution of the ionic conduction to the electrical properties in the PbSe CQD film became significant after ligand removal using ammonium sulfide [(NH4)(2)S], evidenced by temperature-dependent FET mobility, threshold voltage, and current hysteresis depending on gate scan direction. The enhanced FET mobility and increased carrier concentration at a lower temperature are attributed to reduced ionic conduction, suppressing the gate electric field screening at the PbSe/SiO2 interface.