Ultrafast Imaging of Carrier Transport across Grain Boundaries in Hybrid Perovskite Thin Films

Kai Zhu, Mengjin Yang, Jordan Snaider, Zhi Guo, Ti Wang, Long Yuan, Libai Huang

Research output: Contribution to journalArticlepeer-review

56 Scopus Citations

Abstract

For optoelectronic devices based on polycrystalline semiconducting thin films, carrier transport across grain boundaries is an important process in defining efficiency. Here we employ transient absorption microscopy (TAM) to directly measure carrier transport within and across the boundaries in hybrid organic-inorganic perovskite thin films for solar cell applications with 50 nm spatial precision and 300 fs temporal resolution. By selectively imaging sub-bandgap states, our results show that lateral carrier transport is slowed down by these states at the grain boundaries. However, the long carrier lifetimes allow for efficient transport across the grain boundaries. The carrier diffusion constant is reduced by about a factor of 2 for micron-sized grain samples by the grain boundaries. For grain sizes on the order of ∼200 nm, carrier transport over multiple grains has been observed within a time window of 5 ns. These observations explain both the shortened photoluminescence lifetimes at the boundaries as well as the seemingly benign nature of the grain boundaries in carrier generation.

Original languageAmerican English
Pages (from-to)1402-1408
Number of pages7
JournalACS Energy Letters
Volume3
Issue number6
DOIs
StatePublished - 8 Jun 2018

Bibliographical note

Publisher Copyright:
© 2018 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-71299

Keywords

  • carrier transport
  • optoelectronic devices
  • polycrystalline
  • semiconducting thin films

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