One‐Dimensional Molecular Metal Halide Materials: Structures, Properties, and Applications

Abstract

Metal halides with low‐dimensional molecular structures are the rising stars in the horizon of functional materials research. Among them, 1D metal halide hybrids are very promising for future optoelectronic applications because of their unusual photophysical properties resulting from strong quantum confinement. In the past few years, besides lead‐based 1D metal halide hybrids, research has been extended to lead‐free organic and all‐inorganic metal halides. Due to near‐unity photoluminescence quantum yield and excellent structural stability, all‐inorganic 1D metal halides are suitable for environmentally friendly optoelectronic devices. Moreover, the distortion and connectivity mode of metal halide octahedra arouse the formation of self‐trapped excitons within 1D metal halides, thus endowing the materials with distinct optical properties. Recent investigations have revealed many exciting characteristics of this new class of materials, such as ferroelectricity, ferromagnetism, optical cooling, and so on. This perspective presents not only structure–property correlations and recent applications of 1D metal halides but also the existing challenges and future research directions.

Metal Halide Semiconductors beyond Lead-Based Perovskites for Promising Optoelectronic Applications

“…Strictly speaking, this type of low-dimensional metal halides does not have an ABX 3 or equivalent stoichiometry and are not considered as “perovskites”; we therefore classify them as perovskite-like materials . At present, the research on this kind of emerging low-dimensional materials is still in the initial phase; more attention is focused on the fundamental investigations such as electronic, optical, and photophysical properties . For example, the corner-sharing zigzag chainlike hybrid material (C 6 H 13 N) 2 BiI 5 shows a direct band gap of 2.02 eV, long-lived photoluminescence, and visible light detection capabilities.…”

“…108 At present, the research on this kind of emerging low-dimensional materials is still in the initial phase; more attention is focused on the fundamental investigations such as electronic, optical, and photophysical properties. 109 For example, the corner-sharing zigzag chainlike hybrid material (C 6 H 13 N) 2 BiI 5 shows a direct band gap of 2.02 eV, long-lived photoluminescence, and visible light detection capabilities. It is expected to be a possible candidate for light absorption in optoelectronic applications.…”

A One-Dimensional Broadband Emissive Hybrid Lead Iodide with Face-Sharing PbI6 Octahedral Chains

“…Broadband STE emissions of low-dimensional metal halides were first reported in 2D layered Pb–Cl and Pb–Br perovskites by Dohner et al in 2014, , largely triggering the boom of this sort of materials, while at that time the luminescence of analogous Pb–I slabs was commonly dominated by a narrowband free exciton (FE) emission. , Subsequently, it was found that STE and FE emissions can coexist in 1D or 2D lead iodides, − in which the former is usually weaker than the latter. ,, In contrast to 2D counterparts, 1D lead-based hybrid systems with unique core–shell quantum wire structures hold greater structural adjustability and tunable photoluminescence (PL) properties. − For instance, the corrugated 1D structure based on double-edge-shared octahedral PbBr 6 2– units , shows an initial PL quantum yield (PLQY) of 10%, which is significantly elevated to 100% at a pressure of 3 GPa . In addition, the 1D postperovskite type chains constructed by the corner-sharing dimers with edge-sharing PbX 6 (X = Cl, Br, and I) octahedra show tunable, broadband luminescence properties , and high PLQY (60%); in such a nice system, the nature of halogen significantly governs the intensity of the resulting broadband emission through tuning the excitonic self-trapping depth (Cl > Br > I) .…”

New Low-Dimensional Hybrid Perovskitoids Based on Lead Bromide with Organic Cations from Charge-Transfer Complexes

“…The 1D-infinite chains along the crystallographic axis a (Figure 2 top) are made from the lead bromide octahedra (Pb-Br 2.8569(9)-3.3482(10) Å), which are more distorted than in the above 1D-perovskitoid [AntrNH 3 ][PbBr 3 ](DMF) as gauged by a continuous symmetry measure (Table 2). Each of them is connected to two other octahedra through a popular face-sharing mode often found in 1D-perovskitoids [12,35] and associated with a significant increase in the band gap [48,49].…”

“…As a solution [4,5], low-dimensional hybrid perovskites [3] were proposed in which MX 6 octahedra or MX 5 pyramids [6] are corner-shared in less than three dimensions. A wider choice of organic cations [7], which no longer have to meet strict size requirements [8,9], allows obtaining 2D- [10], 1D- [11,12] or 0D- [13] hybrid perovskites with promising optoelectronic properties. To further improve their performance in solar cells [14], inert organic cations are sometimes replaced [15] by electroactive molecules [16][17][18][19][20], including those encountered in organic charge-transfer complexes [18,[21][22][23][24].…”