Imaging Heterogeneously Distributed Photo-Active Traps in Perovskite Single Crystals

Haifeng Yuan, Elke Debroye, Eva Bladt, Gang Lu, Masoumeh Keshavarz, Kris P.F. Janssen, Maarten B.J. Roeffaers, Sara Bals, Edward H. Sargent*, Johan Hofkens

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

28 Scopus citations

Abstract

Organic–inorganic halide perovskites (OIHPs) have demonstrated outstanding energy conversion efficiency in solar cells and light-emitting devices. In spite of intensive developments in both materials and devices, electronic traps and defects that significantly affect their device properties remain under-investigated. Particularly, it remains challenging to identify and to resolve traps individually at the nanoscopic scale. Here, photo-active traps (PATs) are mapped over OIHP nanocrystal morphology of different crystallinity by means of correlative optical differential super-resolution localization microscopy (Δ-SRLM) and electron microscopy. Stochastic and monolithic photoluminescence intermittency due to individual PATs is observed on monocrystalline and polycrystalline OIHP nanocrystals. Δ-SRLM reveals a heterogeneous PAT distribution across nanocrystals and determines the PAT density to be 1.3 × 1014 and 8 × 1013 cm−3 for polycrystalline and for monocrystalline nanocrystals, respectively. The higher PAT density in polycrystalline nanocrystals is likely related to an increased defect density. Moreover, monocrystalline nanocrystals that are prepared in an oxygen- and moisture-free environment show a similar PAT density as that prepared at ambient conditions, excluding oxygen or moisture as chief causes of PATs. Hence, it is concluded that the PATs come from inherent structural defects in the material, which suggests that the PAT density can be reduced by improving crystalline quality of the material.

Original languageEnglish (US)
Article number1705494
JournalAdvanced Materials
Volume30
Issue number13
DOIs
StatePublished - Mar 27 2018

Keywords

  • defects
  • lead iodide perovskite nanocrystals
  • photo-active traps
  • photoluminescence
  • super-resolution optical microscopy

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • General Materials Science

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