Persistent Coulomb Blockade Across the Metal-Insulator Transition in Nanoparticle Solids
Davis G Unruh1, Chase Hansen1, Alberto Camjayi2, Marcelo Rozenberg3, Gergely Zimanyi1
1UC Davis, Davis, CA, United States
/2Universidad de Buenos Aires, Buenos Aires, Argentina
/3CNRS, Paris, France

Nanoparticle systems are a particularly promising class of solar cells. Their performance is limited by low carrier mobility. One driver for the low mobility is that these systems are in their insulating phase. A second is the Coulomb blockade suppressing transport. The insulating behavior can be overcome by driving the nanoparticle layers across a Metal-Insulator Transition (MIT). Up to now, however, it has not been studied whether crossing the MIT also dissolves the Coulomb blockade, or does that persist even as the system enters the metallic phase.
We analyze carrier transport in the insulating phase by our Hierarchical Nanoparticle Transport Simulator (HiNTS), based on a Kinetic Monte Carlo technique. The system is driven into the metallic phase by increasing the inter-nanoparticle coupling. Here we characterize the mobility by the powerful Dynamical Mean-Field Theory (DMFT). Our main and unexpected result is that the Coulomb blockade strongly persists across the MIT phase transition. A key message of our work for the design of nanoparticle PV is that even after the nanoparticle layers are pushed into the metallic regime, the mobility of the layers will critically depend on the carrier density, with the highest mobilities near half integer electron filling.