Isothermal pressure-derived metastable states in 2D hybrid perovskites showing enduring bandgap narrowing

Abstract

Materials in metastable states, such as amorphous ice and supercooled condensed matter, often exhibit exotic phenomena. To date, achieving metastability is usually accomplished by rapid quenching through a thermodynamic path function, namely, heating-cooling cycles. However, heat can be detrimental to organic-containing materials because it can induce degradation. Alternatively, the application of pressure can be used to achieve metastable states that are inaccessible via heating-cooling cycles. Here we report metastable states of 2D organic-inorganic hybrid perovskites reached through structural amorphization under compression followed by recrystallization via decompression. Remarkably, such pressure-derived metastable states in 2D hybrid perovskites exhibit enduring bandgap narrowing by as much as 8.2% with stability under ambient conditions. The achieved metastable states in 2D hybrid perovskites via compression-decompression cycles offer an alternative pathway toward manipulating the properties of these "soft" materials.

Organic‐Inorganic Hybrid Perovskite Single Crystals: Crystallization, Molecular Structures, and Bandgap Engineering

“…When the organics in the perovskite structures are changed, the metal-halogen bond lengths and the XÀ PbÀ X angles are altered, allowing the tuning of band structures and bandgaps. [114][115][116][117] For example, the bandgap of FASnI 3 is~1.46 eV, which is larger than MASnI 3 (~1.15 eV). It is probably because FA is larger than MA, which results in a cubic structure with a larger lattice.…”

“…Furthermore, organic cations can be replaced and the bandgap can be changed. When the organics in the perovskite structures are changed, the metal‐halogen bond lengths and the X−Pb−X angles are altered, allowing the tuning of band structures and bandgaps . For example, the bandgap of FASnI 3 is ∼1.46 eV, which is larger than MASnI 3 (∼1.15 eV).…”

Pressure‐Induced Broadband Emission of 2D Organic–Inorganic Hybrid Perovskite (C6H5C2H4NH3)2PbBr4

“…On the contrary, the vibrational spectra over the 200-1700 cm −1 range are attributable to the PEA + organic cations. [21] With the notable layer-to-layer compression, the enhancement orbital overlap of Pb s and Br p states pushes the valence band maximum as the electronic band dispersion increases. Upon compression to 7.6 GPa, broad weak vibrational bands appeared in the low-frequency range.…”

Large Band Gap Narrowing and Prolonged Carrier Lifetime of (C4H9NH3)2PbI4 under High Pressure

“…[24] Therefore, by combining the structural stability of 2D perovskites and pressure effects, better optoelectronic performance is expected at high pressure. [30][31][32] Matsuishi et al [31] and Liu et al [30] studied the band gap transition of BA 2 PbI 4 and observed several transitions during compression. [30][31][32] Matsuishi et al [31] and Liu et al [30] studied the band gap transition of BA 2 PbI 4 and observed several transitions during compression.…”