n-Type Conducting CdSe Nanocrystal Solids

A bottleneck limiting the widespread application of semiconductor nanocrystal solids is their poor conductivity. We report that the conductivity of thin films of n-type CdSe nanocrystals increases by many orders of magnitude as the occupation of the first two electronic shells, 1S_e and 1P_e, increases, either by potassium or electrochemical doping. Around half-filling of the 1S_e shell, a peak in the conductivity is observed, indicating shell-to-shell transport. Introducing conjugated ligands between nanocrystals increases the conductivities of these states to ~10^-2 siemens per centimeter.