Microstructural Evaluation of Phase Instability in Large Bandgap Metal Halide Perovskites

Dohyung Kim, Jihoo Lim, Seungmin Lee, Arman Mahboubi Soufiani, Eunyoung Choi, Anton V. Ievlev, Nikolay Borodinov, Yongtao Liu, Olga S. Ovchinnikova, Mahshid Ahmadi, Sean Lim, Pankaj Sharma, Jan Seidel, Jun Hong Noh, Jae Sung Yun

Research output: Contribution to journalArticlepeer-review

8 Citations (Scopus)


The optoelectronic performance of organic-inorganic halide perovskite (OIHP)-based devices has been improved in recent years. Particularly, solar cells fabricated using mixed-cations and mixed-halides have outperformed their single-cation and single-halide counterparts. Yet, a systematic evaluation of the microstructural behavior of mixed perovskites is missing despite their known composition-dependent photoinstability. Here, we explore microstructural inhomogeneity in (FAPbI3)x(MAPbBr3)1-x using advanced scanning probe microscopy techniques. Contact potential difference (CPD) maps measured by Kelvin probe force microscopy show an increased fraction of grains exhibiting a low CPD with flat topography as MAPbBr3 concentration is increased. The higher portion of low CPD contributes to asymmetric CPD distribution curves. Chemical analysis reveals these grains being rich in MA, Pb, and I. The composition-dependent phase segregation upon illumination, reflected on the emergence of a low-energy peak emission in the original photoluminescence spectra, arises from the formation of such grains with flat topology. Bias-dependent piezo-response force microscopy measurements, in these grains, further confirm vigorous ion migration and cause a hysteretic piezo-response. Our results, therefore, provide insights into the microstructural evaluation of phase segregation and ion migration in OIHPs pointing toward process optimization as a mean to further enhance their optoelectronic performance.

Original languageEnglish
Pages (from-to)20391-20402
Number of pages12
JournalACS nano
Issue number12
Publication statusPublished - 2021 Dec 28

Bibliographical note

Publisher Copyright:
© 2021 American Chemical Society.


  • contact potential difference
  • defects
  • flat grains
  • inhomogeneity
  • ion migration
  • large bandgap perovskites
  • phase instability

ASJC Scopus subject areas

  • General Materials Science
  • General Engineering
  • General Physics and Astronomy


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