Photoconduction in Annealed and Chemically Treated CdSe/ZnS Inorganic Nanocrystal Films

We present a study of photoconductivity in close-packed films of CdSe/ZnS core/shell nanocrystals, from which the majority of the organic ligands are removed. The ZnS inorganic shells separate the CdSe cores, and passivate the surface of the CdSe nanocrystals, slowing the nonradiative exciton decay rate. These films retain the size-dependent quantum-confined electronic properties of the nanocrystals, including the tunability of their band gap. We demonstrate that replacing the organic ligands, which form the tunnel barrier between nanocrystals in films of CdSe nanocrystals, with the inorganic ZnS shell results in photoconduction with near unity internal quantum efficiency at room temperature.