Temperature and size dependence of the optical properties of tetrapod-shaped colloidal nanocrystals exhibiting type-II transitions

Giovanni Morello*, Angela Fiore, Rosanna Mastria, Andrea Falqui, Alessandro Genovese, Arianna Cretì, Mauro Lomascolo, Isabella R. Franchini, Liberato Manna, Fabio Della Sala, Roberto Cingolani, Milena De Giorgi

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

17 Scopus citations

Abstract

We have investigated the optical properties of colloidal seed-grown CdSe (seed)/CdTe (arms) nanotetrapods both experimentally and computationally. The tetrapods exhibit a type-II transition arising from electrons localized in the CdSe seed region and holes delocalized in the CdTe arms, along with a residual type-I recombination in long-arm tetrapods. Experiments and theory helped to identify the origin of both types of transitions and their size dependence. In particular, time-resolved experiments performed at 10 K evidenced a size-dependent, long living type-II radiative emission arising from the peculiar electron-hole wave function localization. Temperature-dependent photoluminescence (PL) studies indicate that, at high temperature (>150 K), the main process limiting the PL quantum efficiency of the type-I PL is thermal escape of the charge carriers through efficient exciton-optical phonon coupling. The type-II PL instead is limited both by thermal escape and by the promotion of electrons from the conduction band of the seed region to that of the arms, occurring at T > 200 K.

Original languageEnglish (US)
Pages (from-to)18094-18104
Number of pages11
JournalJournal of Physical Chemistry C
Volume115
Issue number37
DOIs
StatePublished - Sep 22 2011

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Energy(all)
  • Physical and Theoretical Chemistry
  • Surfaces, Coatings and Films

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