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 language | English |
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Pages (from-to) | 23908-23921 |
Number of pages | 14 |
Journal | ACS Applied Materials and Interfaces |
Volume | 15 |
Issue number | 19 |
DOIs | |
State | Published - 17 May 2023 |
Bibliographical note
Publisher Copyright:© 2023 The Authors. Published by American Chemical Society.
Funding
S.K. thanks Drs. Shay Tirosh for valuable discussions and Pallavi Singh for experimental help. S.K. acknowledges funding from the Israel Council of Higher Learning for a Planning and Budgeting Committee Postdoctoral Fellowship at Bar Ilan University, BIU. A.I. thanks the Israel Ministry of Science & Technology Ph.D. fellowship support at BIU. At the Weizmann Institute of Science, the work was supported by the Minerva Centre for Self-Repairing Systems for Energy & Sustainability and the Sustainability and Energy Research Initiative (SAERI). L.H. and K.R. acknowledge the support of the Irving and Cherna Moskowitz Center for Nano and Bio-Imaging at the Weizmann Institute of Science.
Funders | Funder number |
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Irving and Cherna Moskowitz Center for Nano | |
Israel Council of Higher Learning | |
Minerva Centre for Self-Repairing Systems for Energy & Sustainability | |
Sustainability and Energy Research Initiative | |
Weizmann Institute of Science | |
Bar-Ilan University | |
Ministry of science and technology, Israel |
Keywords
- 2D/3D
- halide perovskite
- in situ monitoring
- ultrathin
- vapor-phase growth