Successive Phase Transitions and Dual Dielectric Switching in an Organic–Inorganic Hybrid Perovskite

Abstract

Molecular phase transition compounds have become a hot research area in recent years because of their potential as functional materials, such as ferroelectrics, ferroelastics, dielectric switches, etc. However, materials combining switchable dielectric properties and ferroelasticity are still rare. Here, we reported an organic–inorganic hybrid perovskite, [CPtmp]­[Cd­(SCN)3] (1) ([CPtmp]+ is a cyclopentyltrimethylphosphonium cation), with a potential ferroelastic property. This material undergoes three structural phase transitions at 247/226, 335/312, and 349/341 K (upon heating/cooling). The successive phase transitions are mainly caused by the stepwise ordering of [CPtmp]+ cations and the concomitant deformation of [Cd­(SCN)3]− anionic chains revealed by structural analyses, which triggers the double-step dielectric switching in 1 as well. These results would inspire further exploration on molecular dielectric switches with ferroelastic properties.

A Photoluminescent Lead Bromide Hybrid Perovskite Molecular Ferroelastic Semiconductor with Sequential High-Tc Phase Transitions

“…The spontaneous strain of the monoclinic phase at room temperature can be calculated to be X s = √2 e 13 = 0.067, which is comparable to the reported value of spontaneous strain related to the monoclinic phase. ,, …”

“…Spontaneous strain tensor X s of orientation states S 1 and S 2 in the monoclinic phase is given as 48 The spontaneous strain of the monoclinic phase at room temperature can be calculated to be X s = √2e 13 = 0.067, which is comparable to the reported value of spontaneous strain related to the monoclinic phase. 30,49,50 For the lead bromide perovskite architecture, [DMEA]PbBr 3 is expected to have semiconducting and optical properties. As shown in Figure 5a, the UV−vis absorption spectrum displays a sharp absorption edge around 375 nm, which is consistent with the colorless crystal appearance.…”

(C7H18N2)PbI4: A 2D Hybrid Perovskite Solid-State Phase Transition Material with Semiconducting Properties

“…In terms of the structure, the general formulas for the most popular 2D OIHPs are (RNH 3 ) 2 [PbI 4 ] and (NH 3 RNH 3 )­PbI 4 , in which R stands for an organic functional group . The flexibility and adjustability of the structures are shown through organic cation replacement. − Organic cations with different radii, configurations, and interactions with hydrogen bonds will lead to the deformation of the inorganic layers of 2D OIHPs and thus determine the semiconductor properties of the 2D material. − For instance, the results show that weakly Pb–I–Pb distorted (methylhydrazinium) 2 PbI 4 (170.3 and 180°) has a smaller band gap in comaprison to the strongly distorted CsGAPbI 4 (149.74 and 165.19°). , In addition, for iodine-based perovskites, the I···I distance also has an effect on the band gap. Due to the shorter distance of (3AMP)­PbI 4 (4.18 Å), the band gap of (3AMP)­PbI 4 (2.23 eV) is smaller than that of (4AMP)­PbI 4 (2.38 eV) …”

Band gap modulation of organic–inorganic Sb(iii) halide by molecular design

“…30,31 Sb has also been used in the preparation of calcium halophosphate phosphor, so the fluorescence properties of these four substances were also investigated. [32][33][34][35][36][37] As shown in Fig. 3, the photoluminescence excitation (PLE) and emission (PL) spectra of crystals 1-4 at an excitation wavelength of 382 nm each displayed three emission peaks, at 468 nm, 553 nm, 592 nm.…”