Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films

Mengjin Yang, Joseph Berry, Kai Zhu, Samuel Berweger, Gordon MacDonald, Kevin Coakley, Frank DelRio, Thomas Wallis, Pavel Kabos

Research output: Contribution to journalArticlepeer-review

24 Scopus Citations

Abstract

We perform scanning microwave microscopy (SMM) to study the spatially varying electronic properties and related morphology of pristine and degraded methylammonium lead-halide (MAPI) perovskite films fabricated under different ambient humidity. We find that higher processing humidity leads to the emergence of increased conductivity at the grain boundaries but also correlates with the appearance of resistive grains that contain PbI2. Deteriorated films show larger and increasingly insulating grain boundaries as well as spatially localized regions of reduced conductivity within grains. These results suggest that while humidity during film fabrication primarily benefits device properties due to the passivation of traps at the grain boundaries and self-doping, it also results in the emergence of PbI2-containing grains. We further establish that MAPI film deterioration under ambient conditions proceeds via the spatially localized breakdown of film conductivity, both at grain boundaries and within grains, due to local variations in susceptibility to deterioration. These results confirm that PbI2 has both beneficial and adverse effects on device performance and provide new means for device optimization by revealing spatial variations in sample conductivity as well as morphological differences in resistance to sample deterioration.

Original languageAmerican English
Pages (from-to)1796-1801
Number of pages6
JournalNano Letters
Volume17
Issue number3
DOIs
StatePublished - 2017

Bibliographical note

Publisher Copyright:
© 2017 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-67998

Keywords

  • atomic force microscope
  • microwave
  • near-field
  • perovskite
  • photovoltaic

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