Temperature and Size Dependence of the Optical Properties of Tetrapod-Shaped Colloidal Nanocrystals Exhibiting Type-II Transitions

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• 作者：Giovanni Morello ; Angela Fiore ; Rosanna Mastria ; Andrea Falqui ; Alessandro Genovese ; Arianna Creti虁 ; Mauro Lomascolo ; Isabella R. Franchini ; Liberato Manna ; Fabio Della Sala ; Roberto Cingolani ; Milena De Giorgi
• 刊名：Journal of Physical Chemistry C
• 出版年：2011
• 出版时间：September 22, 2011
• 年：2011
• 卷：115
• 期：37
• 页码：18094-18104
• 全文大小：1192K
• 年卷期：v.115,no.37(September 22, 2011)
• ISSN：1932-7455

文摘

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鈥揾ole 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.