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Authors: B. De Geyter, Houtepen, Arjan J., Carrillo, Sergio, P. Geiregat, Gao, Yunan, Ten Cate, Sybren, Schins, Juleon M., D. Van Thourhout, Delerue, Cristophe, Siebbeles, Laurens D.A., Hens, Zeger
Title: Broadband and Picosecond Intraband Relaxation in Lead-Based Colloidal Quantum Dots
Format: International Journal
Publication date: 6/2012
Journal/Conference/Book: ACS Nano
Volume(Issue): 6(7) p.6067–6074
Internal Reference: [N-1320]
DOI:
Download: Download this Publication (1022KB) (1022KB)

Abstract

Using femtosecond transient absorption spectroscopy, we demonstrate that lead chalcogenide nanocrystals show considerable photoinduced absorption (PA) in a broad wavelength range just below the band gap. The time-dependent decay of the PA signal correlates with the recovery of the band gap absorption, indicating that the same carriers are involved. On this basis, we assign this PA signal to intraband absorption, that is, the excitation of photogenerated carriers from the bottom of the conduction band or the top of the valence band to higher energy levels in the conduction and valence band continuum. We confirm our experiments with tight-binding calculations. This broadband response in the commercially interesting near- to mid-infrared range is very relevant for ultra-high-speed all-optical signal processing. We benchmark the performance with bulk Si and Si nanocrystals.

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