Temperature-, gate-, and photoinduced conductance of close-packedCdTenanocrystal films

We measure the conductance of close-packed films of $\mathrm{CdTe}$ 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 $\mathrm{CdTe}$ nanocrystal films, and that the hole density can be modulated with gate voltage. Secondary photocurrents have a photoconductive gain of $\sim 10$ at ${10}^6\mathrm{V}∕\mathrm{cm}$ 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.