title: Mapping the exciton diffusion in semiconductor nanocrystal solids.
abstract: Colloidal nanocrystal solids represent an emerging class of functional materials that hold strong promise for device applications. The macroscopic properties of these disordered assemblies are determined by complex trajectories of exciton diffusion processes, which are still poorly understood. Owing to the lack of theoretical insight, experimental strategies for probing the exciton dynamics in quantum dot solids are in great demand. Here, we develop an experimental technique for mapping the motion of excitons in semiconductor nanocrystal films with a subdiffraction spatial sensitivity and a picosecond temporal resolution. This was accomplished by doping PbS nanocrystal solids with metal nanoparticles that force the exciton dissociation at known distances from their birth. The optical signature of the exciton motion was then inferred from the changes in the emission lifetime, which was mapped to the location of exciton quenching sites. By correlating the metal-metal interparticle distance in the film with corresponding changes in the emission lifetime, we could obtain important transport characteristics, including the exciton diffusion length, the number of predissociation hops, the rate of interparticle energy transfer, and the exciton diffusivity. The benefits of this approach to device applications were demonstrated through the use of two representative film morphologies featuring weak and strong interparticle coupling.
authors: Natalia
authors: N
authors: Kholmicheva
authors: Pavel
authors: P
authors: Moroz
authors: §Department of Physics, University of Toledo, Toledo, Ohio 43606, United States.
authors: Ebin
authors: E
authors: Bastola
authors: Natalia
authors: N
authors: Razgoniaeva
authors: ∥Department of Chemistry and Biochemistry, St. Mary's University, San Antonio, Texas 78228, United States.
authors: Jesus
authors: J
authors: Bocanegra
authors: ∥Department of Chemistry and Biochemistry, St. Mary's University, San Antonio, Texas 78228, United States.
authors: Martin
authors: M
authors: Shaughnessy
authors: Zack
authors: Z
authors: Porach
authors: ∥Department of Chemistry and Biochemistry, St. Mary's University, San Antonio, Texas 78228, United States.
authors: Dmitriy
authors: D
authors: Khon
authors: Mikhail
authors: M
authors: Zamkov
mesh_terms: D004058:Diffusion; D004583:Electrons; D004735:Energy Transfer; D007854:Lead / Q000737:chemistry; D045663:Quantum Dots / Q000737:chemistry*; D012666:Semiconductors; D013050:Spectrometry, Fluorescence; D013440:Sulfides / Q000737:chemistry
chemical_list: D013440:Sulfides; C018391:lead sulfide; D007854:Lead
keywords: charge transport; colloidal quantum dots; plasmonics; thin films