Temperature-, gate-, and photoinduced conductance of close-packed CdTe nanocrystal films

We measure the conductance of close-packed films of CdTe nanocrystals in field-effect structures in the dark and in the presence of light. We find that the majority carriers are holes, that they are injected from gold electrodes into the CdTe nanocrystal films, and that the hole density can be modulated with gate voltage. Secondary photocurrents have a photoconductive gain of similar to 10 at 10(6) V/cm showing that the hole mobility is higher than the electron mobility. A single phenomenological description of the field dependence of the hole mobility can explain the dependence of current on source-drain voltage for both dark and light currents.