Influence of Annealing and Composition on the Crystal Structure of Mixed-Halide, Ruddlesden-Popper Perovskites

Niara Wright, Xixi Qin, Junwei Xu, Leah Kelly, Steven Harvey, Michael Toney, Volker Blum, Adrienne Stiff-Roberts

Research output: Contribution to journalArticlepeer-review

27 Scopus Citations

Abstract

Mixed-halide two-dimensional (2D) hybrid organic-inorganic perovskites offer an important opportunity to control the band gap for applications in optoelectronic devices. This study focuses on phenethylammonium lead halide [(PEA)2Pb(I1-xBrx)4] films, the pure iodide form of which is one of the most widely studied optically active 2D perovskite systems. Resonant infrared, matrix-assisted pulsed laser evaporation is used to grow films to explore the effects of post-growth annealing and mixed-halide composition. The composition, crystal structure, and optical properties are studied for as-grown and annealed films of (PEA)2Pb(I1-xBrx)4 for x = 0, 0.25, 0.5, 0.75, and 1. First-principles calculations are used in conjunction with the experimental data to explain the mixed-halide behavior that does not trend monotonically with the bromide content. Important results of this work are as follows: (i) X-ray diffraction reveals evidence for halide phase separation around x = 0.25, consistent with first-principles calculations, whereas no phase separation is observed for x = 0.5 and above and (ii) a unique photoluminescence (PL) peak splitting is observed for x = 0.75, a composition for which no compositional phase separation is observed. The PL splitting is tentatively explained by the coexistence of two distinct types of halide short-range ordering at x = 0.75. Overall, this study demonstrates that mixed-halide n = 1 Ruddlesden-Popper perovskites are not simple random alloys but that instead, they display distinct sites and ordering preferences of the different halide anions. These preferences are critical to understand and rationally tune the properties of the materials.

Original languageAmerican English
Pages (from-to)3109-3122
Number of pages14
JournalChemistry of Materials
Volume34
Issue number7
DOIs
StatePublished - 12 Apr 2022

Bibliographical note

Publisher Copyright:
© 2022 The Authors. Published by American Chemical Society and Division of Chemical Education, Inc.

NREL Publication Number

  • NREL/JA-5K00-81937

Keywords

  • annealing
  • calculations
  • crystal structure
  • energy gap
  • lead compounds
  • optical properties
  • optoelectronic devices
  • organic-inorganic materials
  • perovskite
  • phase separation

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