title: Size-Independent Exciton Localization Efficiency in Colloidal CdSe/CdS Core/Crown Nanosheet Type-I Heterostructures.
abstract: CdSe/CdS core/crown nanoplatelet type I heterostructures are a class of two-dimensional materials with atomically precise thickness and many potential optoelectronic applications. It remains unclear how the precise thickness and lack of energy disorder affect the properties of exciton transport in these materials. By steady-state photoluminescence excitation spectroscopy and ultrafast transient absorption spectroscopy, we show that in five CdSe/CdS core/crown structures with the same core and increasing crown size (with thickness of ∼1.8 nm, width of ∼11 nm, and length from 20 to 40 nm), the crown-to-core exciton localization efficiency is independent of crown size and increases with photon energy above the band edge (from 70% at 400 nm to ∼100% at 370 nm), while the localization time increases with the crown size. These observations can be understood by a model that accounts for the competition of in-plane exciton diffusion and selective hole trapping at the core/crown interface. Our findings suggest that the exciton localization efficiency can be further improved by reducing interfacial defects.
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States.
authors.forename: Qiuyang
authors.initials: Q
authors.lastname: Li
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States.
authors.forename: Kaifeng
authors.initials: K
authors.lastname: Wu
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States.
authors.forename: Jinquan
authors.initials: J
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States.
authors.forename: Zheyuan
authors.initials: Z
authors.lastname: Chen
authors.affiliation: Department of Chemistry, The Vanderbilt Institute of Nanoscale Science and Engineering, Vanderbilt University , Nashville, Tennessee 37235, United States.
authors.forename: James R
authors.initials: JR
authors.lastname: McBride
authors.affiliation: Department of Chemistry, Emory University , 1515 Dickey Drive, NE, Atlanta, Georgia 30322, United States.
authors.forename: Tianquan
authors.initials: T
authors.lastname: Lian
keywords: 2D materials; colloidal nanosheets; diffusive transport; exciton localization; hot exciton transport; type-I heterostructure