Suppressed blinking and auger recombination in near-infrared type-II InP/CdS nanocrystal quantum dots

Nano Lett. 2012 Nov 14;12(11):5545-51. doi: 10.1021/nl302453x. Epub 2012 Oct 2.

Abstract

Nonblinking excitonic emission from near-infrared and type-II nanocrystal quantum dots (NQDs) is reported for the first time. To realize this unusual degree of stability at the single-dot level, novel InP/CdS core/shell NQDs were synthesized for a range of shell thicknesses (~1-11 monolayers of CdS). Ensemble spectroscopy measurements (photoluminescence peak position and radiative lifetimes) and electronic structure calculations established the transition from type-I to type-II band alignment in these heterostructured NQDs. More significantly, single-NQD studies revealed clear evidence for blinking suppression that was not strongly shell-thickness dependent, while photobleaching and biexciton lifetimes trended explicitly with extent of shelling. Specifically, very long biexciton lifetimes-up to >7 ns-were obtained for the thickest-shell structures, indicating dramatic suppression of nonradiative Auger recombination. This new system demonstrates that electronic structure and shell thickness can be employed together to effect control over key single-dot and ensemble NQD photophysical properties.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cadmium Compounds / chemistry
  • Electronics
  • Electrons
  • Indium / chemistry
  • Microscopy, Electron, Transmission / methods
  • Nanoparticles
  • Nanotechnology / methods
  • Palladium / chemistry
  • Particle Size
  • Phosphates / chemistry
  • Photochemistry / methods
  • Quantum Dots*
  • Spectrometry, Fluorescence / methods
  • Spectroscopy, Near-Infrared / methods*
  • Sulfides / chemistry
  • Temperature
  • Time Factors

Substances

  • Cadmium Compounds
  • Phosphates
  • Sulfides
  • Indium
  • cadmium sulfide
  • Palladium