title: Photoconductivity enhancement in multilayers of CdSe and CdTe quantum dots.
abstract: Charge separation at the interface between CdSe and CdTe quantum dots was investigated by comparing the photoconductivity of films consisting of only CdSe or CdTe quantum dots to that of films with alternating layers of CdSe and CdTe quantum dots. The photoconductivity for alternating layers is three times higher than for the single component layers. Different possible mechanisms are discussed, and it is concluded that the dissociation of photoexcited excitons into spatially separated mobile charge carriers at the CdSe/CdTe QD interfaces is the most likely explanation. Given that the yield of charge carrier photogeneration in the multilayer sample is at most one, and under the assumption that the mobility of QD layers in unchanged, we conclude that the yield of charge carrier photogeneration in the single component samples is at most one-third. The thickness of the individual CdSe and CdTe layers was varied, resulting in different distances between the CdSe/CdTe interfaces. The photoconductivity increased with respect to films of only CdSe or CdTe when these interfaces were separated by only one or two quantum dot layers, which implies that exciton diffusion is inefficient.
authors.affiliation: Department of Chemical Engineering, Delft University of Technology, Julianalaan 136, 2628 BL Delft, The Netherlands.
authors.forename: Elise
authors.initials: E
authors.lastname: Talgorn
authors.forename: Marnix A
authors.initials: MA
authors.lastname: de Vries
authors.forename: Laurens D A
authors.initials: LD
authors.lastname: Siebbeles
authors.forename: Arjan J
authors.initials: AJ
authors.lastname: Houtepen
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry* / Q000528:radiation effects*; D004553:Electric Conductivity; D008027:Light; D008422:Materials Testing; D045663:Quantum Dots; D018036:Selenium Compounds / Q000737:chemistry* / Q000528:radiation effects*; D013691:Tellurium / Q000737:chemistry* / Q000528:radiation effects*
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide; D013691:Tellurium; C028337:cadmium telluride