Suppressing Cation Migration in Triple-Cation Lead Halide Perovskites

Ilia Pavlovetc, Michael Brennan, Sergiu Draguta, Anthony Ruth, Taylor Moot, Jeffrey Christians, Kyle Aleshire, Steve Harvey, Stefano Toso, Sanjini Nanayakkara, Jonah Messinger, Joseph Luther, Masaru Juno

Research output: Contribution to journalArticlepeer-review

57 Scopus Citations

Abstract

Ion migration represents an intrinsic instability of metal halide perovskite solar cells. Here we show that triple-cation FAxMAyCs1-x-yPbI3 [FA+ = (NH2)2CH+, MA+ = CH3NH3+] active layers with mixed orthorhombic, post-perovskite (δortho-CsPbI3), and cubic perovskite (α) phases (i.e., α/δ-phase FAxMAyCs1-x-yPbI3) exhibit improved cation stability against applied bias relative to pure α-phase perovskites (i.e., FA0.85Cs0.15PbI3 and FA0.76MA0.15Cs0.09PbI3). Infrared photothermal heterodyne imaging and time-of-flight secondary ion mass spectrometry are used to visualize exclusive α-phase perovskite lateral device A+ cation accumulation (depletion) at perovskite negative (positive) electrode interfaces. The resulting compositional heterogeneities lead to degradation. Operational stability testing of solar cells reveals similar degradation behavior; α/δ-phase FAxMAyCs1-x-yPbI3 lateral devices/solar cells, by contrast, show improved stabilities. Enhanced α/δ-FAxMAyCs1-x-yPbI3 stability is rationalized by δortho-phase inclusions, acting as barriers through which A+ cations do not easily migrate. This study thus provides new insights into cation migration in FAxMAyCs1-x-yPbI3 perovskites and suggests a materials design strategy toward suppressing cation instabilities in hybrid perovskites.

Original languageAmerican English
Pages (from-to)2802-2810
Number of pages9
JournalACS Energy Letters
Volume5
Issue number9
DOIs
StatePublished - 2020

Bibliographical note

Publisher Copyright:
Copyright © 2020 American Chemical Society.

NREL Publication Number

  • NREL/JA-5900-76887

Keywords

  • cation migration
  • perovskites

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