Hole Mobility in Nanocrystal Solids as a Function of Constituent Nanocrystal Size.

Solids of semiconductor nanocrystals (NCs) are semiconductors in which the band gap can be controlled by changing the size of the constituent NCs. To date, nontrivial dependencies of the carrier mobility on the NC size have been reported. We use the time-of-flight (TOF) technique to measure the carrier mobility as a function of the NC size and find that the hole mobility of the NC solid increases dramatically with decreasing NC radius. We show that this result is in agreement with an analytic model for carrier mobility in NC solids. We further implement Monte Carlo simulations to aid in understanding the transient measurements in the context of models of dispersive transport. This work highlights that changing NC size in a device has important implications for charge transport.