Charge separation in type II tunneling structures of close-packed CdTe and CdSe nanocrystals.
We report on charge separation between type II aligned CdTe and CdSe nanocrystals. Two types of electrostatically bound nanocrystal structures have been studied: first, clusters of nanocrystals hold together by Ca(II) ions in aqueous solution and, second, thin film structures of nanocrystals created with layer-by-layer deposition in combination with polyelectrolytes. In both types of structures, short interparticle distances of less than 1 nm have been achieved, whereby the isolating organic ligands on the nanocrystal surfaces and/or the polymer monolayers act as tunneling barriers between nanocrystals. We have observed an efficient quenching of photoluminescence and a reduced emission lifetime for CdTe nanocrystals in both types of type II heterostructures. This result is explained by a spatial charge separation of the photoexcited electron-hole pairs due to tunneling of charge carriers through the thin organic layer between CdTe and CdSe nanocrystals. Type II heterostructures demonstrated here may find future applications in photovoltaics.
Gross
Dieter
D
Photonics and Optoelectronics Group, Physics Department and Center for NanoScience (CeNS), Ludwig-Maximilians-Universität München, 80799 Munich, Germany.
Susha
Andrei S
AS
Klar
Thomas A
TA
Da Como
Enrico
E
Rogach
Andrey L
AL
Feldmann
Jochen
J
D019187:Cadmium Compounds / Q000737:chemistry*; D003198:Computer Simulation; D004579:Electron Transport; D008956:Models, Chemical; D049329:Nanostructures / Q000737:chemistry* / Q000648:ultrastructure; D036103:Nanotechnology / Q000379:methods*; D010316:Particle Size; D018036:Selenium Compounds / Q000737:chemistry*; D012666:Semiconductors; D055672:Static Electricity; D013691:Tellurium / Q000737:chemistry*
D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide; D013691:Tellurium; C028337:cadmium telluride