title: Temperature dependence of excitonic radiative decay in CdSe quantum dots: the role of surface hole traps.
abstract: Using atomistic, semiempirical pseudopotential calculations, we show that if one assumes the simplest form of a surface state in a CdSe nanocrystal--an unpassivated surface anion site--one can explain theoretically several puzzling aspects regarding the observed temperature dependence of the radiative decay of excitons. In particular, our calculations show that the presence of surface states leads to a mixing of the dark and bright exciton states, resulting in a decrease of 3 orders of magnitude of the dark-exciton radiative lifetime. This result explains the persistence of the zero-phonon emission line at low temperature, for which thermal population of higher-energy bright-exciton states is negligible. Thus, we suggest that surface states are the controlling factor of dark-exciton radiative recombination in currently synthesized colloidal CdSe nanocrystals.
authors.affiliation: National Renewable Energy Laboratory, Golden, CO 80401, USA.
authors.forename: Marco
authors.initials: M
authors.lastname: Califano
authors.forename: Alberto
authors.initials: A
authors.lastname: Franceschetti
authors.forename: Alex
authors.initials: A
authors.lastname: Zunger
mesh_terms: D019187:Cadmium Compounds / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D003102:Colloids / Q000032:analysis / Q000737:chemistry / Q000528:radiation effects; D003460:Crystallization / Q000379:methods*; D006207:Half-Life; D007700:Kinetics; D008027:Light; D008422:Materials Testing; D036103:Nanotechnology / Q000379:methods*; D045663:Quantum Dots; D011829:Radiation Dosage; D011874:Radiometry; D018036:Selenium Compounds / Q000032:analysis / Q000737:chemistry* / Q000528:radiation effects*; D013499:Surface Properties; D013696:Temperature
chemical_list: D019187:Cadmium Compounds; D003102:Colloids; D018036:Selenium Compounds; C058667:cadmium selenide