Coulomb blockade and hopping conduction in PbSe quantum dots.

We report for the first time on rich and tunable transport phenomena in closed-packed arrays of PbSe colloidal nanocrystals (NCs) in the form of thin films. As the interdot coupling is increased, the system evolves from an insulating regime dominated by Coulomb blockade to a semiconducting regime, where hopping conduction is the dominant transport mechanism. The observed phenomena can be interpreted using the framework established mainly in the context of transport measurements in metallic quantum dots and disordered semiconductors.