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Title: Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films

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. Here, 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 PbI 2. 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 PbI 2-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 PbI 2 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.
Authors:
ORCiD logo [1] ;  [1] ;  [2] ;  [1] ;  [2] ;  [2] ;  [1] ;  [1] ;  [1]
  1. National Inst. of Standards and Technology (NIST), Boulder, CO (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Report Number(s):
NREL/JA-5900-67998
Journal ID: ISSN 1530-6984
Grant/Contract Number:
AC36-08GO28308
Type:
Accepted Manuscript
Journal Name:
Nano Letters
Additional Journal Information:
Journal Volume: 17; Journal Issue: 3; Journal ID: ISSN 1530-6984
Publisher:
American Chemical Society
Research Org:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org:
USDOE Office of Energy Efficiency and Renewable Energy (EERE)
Country of Publication:
United States
Language:
English
Subject:
14 SOLAR ENERGY; 77 NANOSCIENCE AND NANOTECHNOLOGY; atomic force microscope; microwave; near-field; perovskite; photovoltaic
OSTI Identifier:
1349016

Berweger, Samuel, MacDonald, Gordon A., Yang, Mengjin, Coakley, Kevin J., Berry, Joseph J., Zhu, Kai, DelRio, Frank W., Wallis, Thomas M., and Kabos, Pavel. Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films. United States: N. p., Web. doi:10.1021/acs.nanolett.6b05119.
Berweger, Samuel, MacDonald, Gordon A., Yang, Mengjin, Coakley, Kevin J., Berry, Joseph J., Zhu, Kai, DelRio, Frank W., Wallis, Thomas M., & Kabos, Pavel. Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films. United States. doi:10.1021/acs.nanolett.6b05119.
Berweger, Samuel, MacDonald, Gordon A., Yang, Mengjin, Coakley, Kevin J., Berry, Joseph J., Zhu, Kai, DelRio, Frank W., Wallis, Thomas M., and Kabos, Pavel. 2017. "Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films". United States. doi:10.1021/acs.nanolett.6b05119. https://www.osti.gov/servlets/purl/1349016.
@article{osti_1349016,
title = {Electronic and Morphological Inhomogeneities in Pristine and Deteriorated Perovskite Photovoltaic Films},
author = {Berweger, Samuel and MacDonald, Gordon A. and Yang, Mengjin and Coakley, Kevin J. and Berry, Joseph J. and Zhu, Kai and DelRio, Frank W. and Wallis, Thomas M. and Kabos, Pavel},
abstractNote = {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. Here, 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.},
doi = {10.1021/acs.nanolett.6b05119},
journal = {Nano Letters},
number = 3,
volume = 17,
place = {United States},
year = {2017},
month = {2}
}