Electrical injection and transport in films of semiconductor nanocrystals

We study injection and transport in thin disordered films of CdSe nanocrystals between metal electrodes. We investigate the current-voltage characteristics of these devices as a function of electrode material, nanocrystal size, and temperature. We also measure the photocurrent response of these devices, and find that the photocurrent action spectra follow the quantum-confined absorption spectra of the nanocrystals. For dissimilar top and bottom electrodes, we find that the devices are highly rectifying. By studying space charge limited currents in these devices, we are able to place a lower bound on the effective carrier mobility in such films, and we find that the effective mobility is strongly field dependent. We find that the conductivity is strongly temperature dependent, and is qualitatively consistent with an activated hopping process at temperatures above 180 K.