Abstract
Ultrafast time-resolved absorption spectroscopy is used to investigate exciton dynamics in CdSe nanocrystal films. The effects of morphology, quantum-dot versus quantum-rod, and preparation of nanocrystals in a thin film form are investigated. The measurements revealed longer intraband exciton relaxation in quantum-rods than in quantum-dots. The slowed relaxation in quantum-rods is due to mitigation of the Auger-relaxation mechanism from elongating the nanocrystal. In addition, the nanocrystal thin film showed long-lived confined acoustic phonons corresponding to the ellipsoidal breathing mode, contrary to others work on colloidal systems of CdSe nanocrystals.
Highlights
It is well known that semiconductor nanocrystals (NCs) exhibit pseudo-molecular electronic band structures
The slowed relaxation in quantum-rods is due to mitigation of the Auger-relaxation mechanism from elongating the nanocrystal
The nanocrystal thin film showed long-lived confined acoustic phonons corresponding to the ellipsoidal breathing mode, contrary to others work on colloidal systems of CdSe nanocrystals
Summary
It is well known that semiconductor nanocrystals (NCs) exhibit pseudo-molecular electronic band structures. The discrete nature of these electronic states in NCs can effectively be modified by controlling chemical synthesis conditions to dictate the final NC shape. It has been shown in various studies, e.g., by Klimov [1,2], Kambhampti [3,4], and Mohamed et al [5] that controlling NC size lends itself to controlling electronic relaxation. Various studies have been performed on colloidal systems of CdSe quantum-dots (QDs) [1,3,4] and quantum-rods (QRs) [5] to investigate the hot-exciton relaxation. We investigate the morphology effect, QD vs. QR, i.e., the effect of the confinement condition on the relaxation pathways in NCs
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