Emerging Characterizing Techniques in the Fine Structure Observation of Metal Halide Perovskite Crystal

Abstract

Driven by its appealing application in the energy harvesting industry, metal halide perovskite solar cells are attracting increasing attention from various fields, such as chemistry, materials, physics, and energy-related industries. While the energy conversion efficiency of the perovskite solar cell is being investigated often by various research groups, the relationship between the surface structure and the property is still ambiguous and, therefore, becomes an urgent topic due to its wide application in the real environment. Recently, the fine structure characterization of perovskite crystals has been analysed by varying techniques, such as XRD, synchrotron-based grazing incidence XRD, XAFS, and STM, in addition to others. In this review article, we will summarize recent progresses in the monitoring of fine nanostructures of the surface and crystal structures of perovskite films, mainly by XAFS, XRD, and STM, focusing on the discussion of the relationship between the properties and the stability of perovskite solar cells. Furthermore, a prospective is given for the development of experimental approaches towards fine structure characterization. perovskite crystals. Furthermore, high-performance single-crystal and planar-type photodetector has also been fabricated using single-crystal metal halide perovskite [21], as well as the narrow-band perovskite single-crystal photodetectors [22].It has been acknowledged that perovskite crystals play an important role in the further promotion of perovskite solar cells' performance and industrial usage, as perovskite crystals have the distinct advantage of high controllability. Therefore, using perovskite crystals to solve one of the main issues of instability in perovskite solar cells might be reasonable. The subsequent question, then, is how to determine the crystal quality and characterize the fine structure, accordingly. Presently, there are several state-of-the-art techniques to achieve the structure determination of perovskite crystals, which will, therefore, be discussed and summarized in this review paper. First, we briefly summarize the growth methods of perovskite crystals with considerable discussion on the quality of perovskite crystals, which are investigated mainly by XRD, GIXRD, and XAFS. This covers reports from the literature, in addition to our own work. Secondly, the surface structures of perovskite crystals are investigated by scanning tunneling microscopy (STM) and are analyzed and compared with reports from the literature. The advantage of STM is that it gives a direct morphology of the perovskite surface with angstrom resolution in real space. Basic Structure of Perovskite CrystalsBefore discussing the approaches of growth of single crystal perovskite, it is worth noting the unit cell of perovskite crystal structure (molecular formula: ABX 3 , as depicted in Figure 1a). There are eight octahedral in one unit cell, where the cation, B, fits into an enclosed octahedral and the cation, A, is situated between the eight octahedral. The stability of the ABX...

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

“…It can be used to grow single crystals for some perovskite materials in particular solvents, in which different solubility can be observed in different temperatures. [52] For example, the solubility of some perovskite materials in an HX-based solvent will decrease with a lower solution temperature. (Figure 1a) [42] In 1987, Weber et al used STL method to grow single crystals of CH 3 NH 3 PbX 3 (X = Cl, Br, I) by cooling a concentrated aqueous solution of HX acid, Pb 2 + and CH 3 NH 3 + from about 100°C to room temperature.…”

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