Ultrahigh Hot Carrier Transient Photocurrent in Nanocrystal Arrays by Auger Recombination

Jianbo Gao, Lyran Kidon, Eran Rabani, A. Paul Alivisatos

Research output: Contribution to journalArticlepeer-review

Abstract

In this report, we show that a new mechanism for carrier transport in solution-processed colloidal semiconductor nanocrystal arrays exists at high excitation intensity on ultrafast time scales and allows for facile intrinsic transport between as-prepared nanocrystals over long distances. By combining a high speed photoconductive switch with an ultrafast laser excitation in a sub-40 ps photoconductor, we observed transient photocurrents with peak densities of 3 × 104 - 106 mA/cm2 in self-assembled PbSe nanocrystals capped with long native oleic acid ligands. The ratio between the transient photocurrent peak and the steady-state dark current is 10 orders of magnitude. The transient mobility at the peak current is estimated to range between 0.5-17.5 cm2/(V s) for the various nanocrystal sizes studied, which is 6 to 9 orders of magnitude higher than the dark current steady-state mobility in PbSe, CdSe, and CdTe nanocrystals capped with native ligands. The results are analyzed using a kinetic model which attributes the ultrahigh transient photocurrent to multiple photogenerated excitons undergoing on-particle Auger recombination, followed by rapid tunneling at high energies. This mechanism is demonstrated for a wide range of PbSe nanocrystals sizes (diameters from 2.7 to 7.1 nm) and experimental parameters. Our observations indicate that native ligand-capped nanocrystal arrays are promising for optoelectronics applications wherein multiple carriers are photoinjected to interband states.

Original languageEnglish
Pages (from-to)4804-4810
Number of pages7
JournalNano Letters
Volume19
Issue number7
DOIs
StatePublished - 10 Jul 2019

Keywords

  • Auger recombination
  • Nanocrystals
  • hot carrier
  • native ligands
  • tunneling transport
  • ultrafast

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