Synthetic Ligand Selection Affects Stoichiometry, Carrier Dynamics, and Trapping in CuInSe2Nanocrystals

Samantha M. Harvey, Daniel W. Houck, Wen Liu, Yuzi Liu, David J. Gosztola, Brian A. Korgel, Michael R. Wasielewski, Richard D. Schaller*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

CuInSe2 nanocrystals exhibit tunable near-infrared bandgaps that bolster utility in photovoltaic applications as well as offer potential as substitutes for more toxic Cd- and Pb-based semiconductor compositions. However, they can present a variety of defect states and unusual photophysics. Here, we examine the effects of ligand composition (oleylamine, diphenylphosphine, and tributylphosphine) on carrier dynamics in these materials. Via spectroscopic measurements such as photoluminescence and transient absorption, we find that ligands present during the synthesis of CuInSe2 nanocrystals impart nonradiative electronic states which compete with radiative recombination and give rise to low photoluminescence quantum yields. We characterize the nature of these defect states (hole vs electron traps) and investigate whether they exist at the surface or interior of the nanocrystals. Carrier lifetimes are highly dependent on ligand identity where oleylamine-capped nanocrystals exhibit rapid trapping (<20 ps) followed by diphenylphosphine (<500 ps) and finally tributylphosphine (>2 ns). A majority of carrier population localizes at indium copper antisites (electrons), copper vacancies (holes), or surface traps (electrons and/or holes), all of which are nonemissive.

Original languageEnglish (US)
Pages (from-to)19588-19599
Number of pages12
JournalACS nano
Volume15
Issue number12
DOIs
StatePublished - Dec 28 2021

Keywords

  • carrier dynamics
  • copper indium selenide
  • defects
  • ligands
  • semiconductor nanocrystals

ASJC Scopus subject areas

  • Materials Science(all)
  • Engineering(all)
  • Physics and Astronomy(all)

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