Reversible Pressure‐Dependent Mechanochromism of Dion–Jacobson and Ruddlesden–Popper Layered Hybrid Perovskites

Abstract

Layered Dion-Jacobson (DJ) and Ruddlesden-Popper (RP) hybrid perovskites are promising materials for optoelectronic applications due to their modular structure. To fully exploit their functionality, mechanical stimuli can be used to control their properties without changing the composition. However, the responsiveness of these systems to pressure compatible with practical applications (<1 GPa) remains unexploited. Hydrostatic pressure is used to investigate the structure-property relationships in representative iodide and bromide DJ and RP 2D perovskites based on 1,4-phenylenedimethylammonium (PDMA) and benzylammonium (BzA) spacers in the 0-0.35 GPa pressure range. Pressure-dependent X-ray scattering measurements reveal that lattices of these compositions monotonically shrink and density functional theory calculations provide insights into the structural changes within the organic spacer layer. These structural changes affect the optical properties; the most significant shift in the optical absorption is observed in (BzA) 2 PbBr 4 under 0.35 GPa pressure, which is attributed to an isostructural phase transition. Surprisingly, the RP and DJ perovskites behave similarly under pressure, despite the different binding modes of the spacer molecules. This study provides important insights into how the manipulation of the crystal structure affects the optoelectronic properties of such materials, whereas the reversibility of their response expands the perspectives for future applications.The ORCID identification number(s) for the author(s) of this article can be found under https://doi.org/10.1002/adma.202108720.

Spacer-Dependent and Pressure-Tuned Structures and Optoelectronic Properties of 2D Hybrid Halide Perovskites

“…The mechanical compression of perovskites can result in modification of the Pb–X bond lengths and angles in the inorganic lattice. The subsequent change in orbital overlap results in modification of the observed optoelectronic properties. − The effects of high pressure on 3D HOIPs, such as MAPbI 3 and FAPbI 3 , have been studied extensively. − More recently, high-pressure studies have been conducted on 2D lead-halide-based HOIPs, mostly focused on those with BA (butylammonium), PMA (phenyl methylammonium), or PEA (phenyl ethylammonium) spacer cations. − However, the effects of different spacer cations on the pressure-tuned optoelectronic properties are still not well understood. For example, the PMA and PEA spacer cations differ only by a CH 2 group, yet the high-pressure behaviors of (PMA) 2 PbI 4 and (PEA) 2 PbI 4 are drastically different.…”

“…In particular, the interplay between organic and inorganic layers in other 2D HOIPs with rigid spacers suggests that the distortion and tilting of the PbI 6 significantly influence the evolution of bandgap energies under high pressure, including the nonmonotonic fluctuation and/or direct-to-indirect transition in bandgaps. ,, The computationally optimized crystal structures of CMA 2 PbI 4 at different pressures, however, suggest that no significant changes occur in bond angles in either the PbI 6 octahedra or the Pb–I–Pb angle between adjacent octahedra, which maintains at approximately 152° upon compression and decompression in the entire pressure region and indicates no significant tilting of the PbI 6 octahedra. The major changes were found to be in the Pb–I bond lengths (Figure S8b) with anisotropic pressure-induced contraction ratios, which leads to some degree of individual PbI 6 octahedral distortion.…”

Crystal growth of two-dimensional organic–inorganic hybrid perovskites and their application in photovoltaics

“…Compared with the R–P and ACI type perovskite, the common thought is that the crystal structure of the D–J type perovskite can be more stable. 205 Li et al 206 used amylammonium (AA) to fabricate the R–P phase AA 2 MA 4 Pb 5 I 16 ( n = 5) as a light absorber layer, and butylammonium iodide (BAI) and 1,4-butanediamine dihydroiodide (BDAI 2 ) were used as the R–P or D–J heterojunction layer to passivate the defect and reduce the non-radiative recombination. The structural stability was examined via monitoring the variation of the XRD spectra in the air with 60% humidity at 20 °C (Fig.…”

Regulation of Quantum Wells Width Distribution in 2D Perovskite Films for Photovoltaic Application

“…In addition, changes in external conditions (temperature, illumination, hydrostatic pressure, magnetic field, etc.) can also affect the arrangement of atoms in the 2D perovskite structure, [100] which is closely related to the formation of QWs with different widths. 2) Clarifying the relationship between pure phase and the properties of 2D perovskite films.…”