Topotactic, Vapor-Phase, In Situ Monitored Formation of Ultrathin, Phase-Pure 2D-on-3D Halide Perovskite Surfaces

Sujit Kumar, Vinayaka H. Damle, Tatyana Bendikov, Anat Itzhak, Michael Elbaum, Katya Rechav, Lothar Houben, Yaakov Tischler, David Cahen

Research output: Contribution to journalArticlepeer-review

1 Scopus citations

Abstract

Two-dimensional (2D) halide perovskites, HaPs, can provide chemical stability to three-dimensional (3D) HaP surfaces, protecting them from exposure to ambient species and from reacting with contacting layers. Both actions occur with 2D HaPs, with the general stoichiometry R2PbI4 (R: long or bulky organic amine) covering the 3D ones. Adding such covering films can also boost power conversion efficiencies of photovoltaic cells by passivating surface/interface trap states. For maximum benefit, we need conformal ultrathin and phase-pure (n = 1) 2D layers to enable efficient tunneling of photogenerated charge carriers through the 2D film barrier. Conformal coverage of ultrathin (<10 nm) R2PbI4 layers on 3D perovskites is challenging with spin coating; even more so is its upscaling for larger-area devices. We report on vapor-phase cation exchange of the 3D surface with the R2PbI4 molecules and real-time in situ growth monitoring by photoluminescence (PL) to determine limits for forming ultrathin 2D layers. We characterize the 2D growth stages, following the changing PL intensity-time profiles, by combining structural, optical, morphological, and compositional characterizations. Moreover, from quantitative X-ray photoelectron spectroscopy (XPS) analysis on 2D/3D bilayer films, we estimate the smallest width of a 2D cover that we can grow to be <5 nm, roughly the limit for efficient tunneling through a (semi)conjugated organic barrier. We also find that, besides protecting the 3D against ambient humidity-induced degradation, the ultrathin 2D-on-3D film also aids self-repair following photodamage.

Original languageEnglish
Pages (from-to)23908-23921
Number of pages14
JournalACS applied materials & interfaces
Volume15
Issue number19
DOIs
StatePublished - 17 May 2023

Bibliographical note

Publisher Copyright:
© 2023 The Authors. Published by American Chemical Society.

Keywords

  • 2D/3D
  • halide perovskite
  • in situ monitoring
  • ultrathin
  • vapor-phase growth

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