title: Evolution of the Single-Nanocrystal Photoluminescence Linewidth with Size and Shell: Implications for Exciton-Phonon Coupling and the Optimization of Spectral Linewidths.
abstract: The optimization of photoluminescence spectral linewidths in semiconductor nanocrystal preparations involves minimizing both the homogeneous and inhomogeneous contributions to the ensemble spectrum. Although the inhomogeneous contribution can be controlled by eliminating interparticle inhomogeneities, far less is known about how to synthetically control the homogeneous, or single-nanocrystal, spectral linewidth. Here, we use solution photon-correlation Fourier spectroscopy (S-PCFS) to measure how the sample-averaged single-nanocrystal emission linewidth of CdSe core and core/shell nanocrystals change with systematic changes in the size of the cores and the thickness and composition of the shells. We find that the single-nanocrystal linewidth at room temperature is heavily influenced by the nature of the CdSe surface and the epitaxial shell, which have a profound impact on the internal electric fields that affect exciton-phonon coupling. Our results explain the wide variations, both experimental and theoretical, in the magnitude and size dependence in previous reports on exciton-phonon coupling in CdSe nanocrystals. Moreover, our findings offer a general pathway for achieving the narrow spectral linewidths required for many applications of nanocrystals.
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Jian
authors.initials: J
authors.lastname: Cui
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Andrew P
authors.initials: AP
authors.lastname: Beyler
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Igor
authors.initials: I
authors.lastname: Coropceanu
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Liam
authors.initials: L
authors.lastname: Cleary
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Avila
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Yue
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: José M
authors.initials: JM
authors.lastname: Cordero
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: S Leigh
authors.initials: SL
authors.lastname: Heathcote
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Daniel K
authors.initials: DK
authors.lastname: Harris
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Ou
authors.initials: O
authors.lastname: Chen
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Jianshu
authors.initials: J
authors.lastname: Cao
authors.affiliation: Department of Chemistry, Massachusetts Institute of Technology , Cambridge, Massachusetts 02139, United States.
authors.forename: Moungi G
authors.initials: MG
authors.lastname: Bawendi
mesh_terms: D002104:Cadmium / Q000737:chemistry; D003102:Colloids / Q000737:chemistry*; D060739:Phonons; D045663:Quantum Dots / Q000737:chemistry*; D012643:Selenium / Q000737:chemistry; D017550:Spectroscopy, Fourier Transform Infrared; D013440:Sulfides / Q000737:chemistry
chemical_list: D003102:Colloids; D013440:Sulfides; D002104:Cadmium; D012643:Selenium
keywords: colloidal quantum dots; exciton−phonon coupling; nanoparticle synthesis; photon-correlation Fourier spectroscopy; semiconductor nanocrystals; single-molecule spectroscopy; spectral linewidth