title: Observation of size-dependent thermalization in CdSe nanocrystals using time-resolved photoluminescence spectroscopy.
abstract: We report heat dissipation times in semiconductor nanocrystals of CdSe. Specifically, a previously unresolved, subnanosecond decay component in the low-temperature photoluminescence decay dynamics exhibits longer decay lifetimes (tens to hundreds of picoseconds) for larger nanocrystals as well as a size-independent, ~25-meV spectral shift. We attribute the fast relaxation to transient phonon-mediated relaxation arising from nonequilibrium acoustic phonons. Following acoustic phonon dissipation, the dark exciton state recombines more slowly via LO-phonon assistance resulting in the observed spectral shift. The measured relaxation time scales agree with classical calculations of thermal diffusion, indicating that interfacial thermal conductivity does not limit thermal transport in these semiconductor nanocrystal dispersions.
authors: Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA.
authors: Daniel C
authors: DC
authors: Hannah
authors: Nicholas J
authors: NJ
authors: Dunn
authors: Sandrine
authors: S
authors: Ithurria
authors: Dmitri V
authors: DV
authors: Talapin
authors: Lin X
authors: LX
authors: Chen
authors: Matthew
authors: M
authors: Pelton
authors: George C
authors: GC
authors: Schatz
authors: Richard D
authors: RD
authors: Schaller
mesh_terms: D019187:Cadmium Compounds / Q000737:chemistry*; D008163:Luminescent Measurements; D053758:Nanoparticles / Q000737:chemistry*; D010316:Particle Size; D018036:Selenium Compounds / Q000737:chemistry*; D013696:Temperature; D013997:Time Factors
chemical_list: D019187:Cadmium Compounds; D018036:Selenium Compounds; C058667:cadmium selenide