Understanding Detrimental and Beneficial Grain Boundary Effects in Halide Perovskites

Gede W. P. Adhyaksa, Sarah Brittman, Haralds Abolins, Andries Lof, Xueying Li, Joel D. Keelor, Yanqi Luo, Teodor Duevski, Ron M. A. Heeren, Shane R. Ellis, David P. Fenning, Erik C. Garnett*

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

75 Citations (Web of Science)

Abstract

Grain boundaries play a key role in the performance of thin-film optoelectronic devices and yet their effect in halide perovskite materials is still not understood. The biggest factor limiting progress is the inability to identify grain boundaries. Noncrystallographic techniques can misidentify grain boundaries, leading to conflicting literature reports about their influence; however, the gold standard - electron backscatter diffraction (EBSD) - destroys halide perovskite thin films. Here, this problem is solved by using a solid-state EBSD detector with 6000 times higher sensitivity than the traditional phosphor screen and camera. Correlating true grain size with photoluminescence lifetime, carrier diffusion length, and mobility shows that grain boundaries are not benign but have a recombination velocity of 1670 cm s(-1), comparable to that of crystalline silicon. Amorphous grain boundaries are also observed that give rise to locally brighter photoluminescence intensity and longer lifetimes. This anomalous grain boundary character offers a possible explanation for the mysteriously long lifetime and record efficiency achieved in small grain halide perovskite thin films. It also suggests a new approach for passivating grain boundaries, independent of surface passivation, to lead to even better performance in optoelectronic devices.

Original languageEnglish
Article number1804792
Number of pages9
JournalAdvanced Materials
Volume30
Issue number52
DOIs
Publication statusPublished - 27 Dec 2018

Keywords

  • amorphous grain boundaries
  • carrier lifetime
  • diffusion length
  • electron backscatter diffraction (EBSD)
  • grain size effect
  • halide perovskites
  • mobility
  • METHYLAMMONIUM LEAD IODIDE
  • SOLAR-CELLS
  • POLYCRYSTALLINE SILICON
  • MULTICRYSTALLINE SILICON
  • DIFFUSION LENGTHS
  • RECOMBINATION
  • FILMS
  • PHOTOLUMINESCENCE
  • PERFORMANCE
  • ENERGY

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