Switchable Color Semiconductors: Methylamine Intercalation, Deintercalation, and Retention in Two-Dimensional Halide Perovskites

Abstract

The low formation energy of metal halide perovskites (MHPs) and their high performance in optoelectronic applications make them rather interesting semiconductor materials. In this work, we take advantage of the tunability of two-dimensional (2D) halide perovskites of the type A2PbI4 to explore a chromogenic mechanism in these materials where methylamine is allowed to intercalate into and deintercalate from the halide perovskite films. Methylamine intercalation results in a change in color from the initial yellow/orange color of the A2PbI4 films to visibly transparent films, while deintercalation leads to a return of a colored film. The reversibility of this solvatochromic mechanism was found to be highly dependent on the nature of the A-site cation used. We observe the formation of iodoplumbate phases, mixed 2D/three-dimensional (3D) perovskites, and/or 3D perovskites as secondary phases formed in some systems and, by exploring a wide array of A2PbI4 materials, we identify key design rules for the A-site cation to limit secondary phase formation and structural changes associated with methylamine intercalation/deintercalation. Specifically, the effects of changing cation–cation, cation “head”-inorganic, and cation “tail”-inorganic interactions in this system are demonstrated. By carefully controlling these interactions, more robust solvatochromic systems are realized. These initial explorations of metal halide solvatochromism improve the understanding of A-site cation design in A2PbI4 MHPs and show that these are a promising class of solvatochromic semiconductors.

Perovskite Smart Windows: The Light Manipulator in Energy‐Efficient Buildings

“…In 2022, Surel et al reported the initial discovery that the yellow PEA 2 PbI 4 (PEA = C 6 H 5 C 2 H 4 NH 3 + ) film underwent a transition to the colorless state upon exposure to CH 3 NH 3 vapor, and reverted back to its original state upon removal of the CH 3 NH 3 vapor (Figure 8a). [94] This color switch phenomenon was also observed in a series of RP-type 2D perovskites by substituting the A site with a series of phenalkylammonium cations. They provided an explanation film upon exposure and removal to CH 3 NH 3 .…”

“…Reproduced with permission. [ 94 ] Copyright 2022, American Chemical Society. b) FAX stripping induced thermochromism of 2D RP‐type perovskite.…”

“…iii,iv Absorbance spectrum traces in 2.3 s showing the fast bleaching and recovery of the PEA 2 PbI 4film upon exposure and removal to CH 3 NH 3 . Reproduced with permission [94]. Copyright 2022, American Chemical Society.…”

Can we make color switchable photovoltaic windows?

“…Somewhat unique to MHPs is the range of mechanisms which provide large changes in transmission, with some material compositions exhibiting several different chromogenic mechanisms. To date, the mechanisms investigated include thermally driven crystal phase transformations, 41,42 hydration [43][44][45] or complexation with other intercalant molecules, [46][47][48][49][50][51][52] changes in structural dimensionality, 53 and other mechanisms besides. 54 This wide range of mechanisms and stimuli has led researchers to imagine many other applications beyond color changing photovoltaic windows, 46,54,55 but those most relevant to windows are discussed here.…”

“…This expansion/contraction can lead to signicant morphological changes aer very few color change cycles. 50,52 Both of these instabilities remain challenging, but work is being done to template both materials 52 and device structures 62 to help relieve these stresses and offer improved device lifetime. Because of these two issues, while it addresses many aspects necessary for switchable photovoltaic windows, this switching mechanism's particular stability issues are likely to be a major hurdle to its development into a product.…”