title: Efficient biexciton emission in elongated CdSe/ZnS nanocrystals.
abstract: We use a combination of low-temperature magneto-optical and lifetime spectroscopies to study the band-edge exciton fine structure of highly photostable single CdSe/ZnS nanocrystals (NCs). Neutral NCs displaying multiline emission spectra and multiexponential photoluminescence (PL) decays are studied as a function of temperature and external magnetic fields. Three different fine structure regimes are identified as a function of the NC aspect ratio. In particular, we identify an optically inactive ground exciton state, whose oscillator strength is tuned up under magnetic field coupling to bright exciton states, and attribute it to the zero angular momentum ground exciton state of elongated NCs. We also show evidence for highly efficient biexciton emission in these NCs, with radiative yields approaching unity in some cases.
authors.affiliation: Laboratoire Photonique Numérique et Nanosciences, Université de Bordeaux , Institut d'Optique Graduate School & CNRS, 351 cours de la libération, 33405 Talence, France.
authors.forename: Y
authors.initials: Y
authors.lastname: Louyer
authors.forename: L
authors.initials: L
authors.lastname: Biadala
authors.forename: J-B
authors.initials: JB
authors.lastname: Trebbia
authors.forename: M J
authors.initials: MJ
authors.lastname: Fernée
authors.forename: Ph
authors.initials: P
authors.lastname: Tamarat
authors.forename: B
authors.initials: B
authors.lastname: Lounis