Synthetic Approaches for Halide Perovskite Thin Films

Abstract

Halide perovskites are an intriguing class of materials that have recently attracted considerable attention for use as the active layer in thin film optoelectronic devices, including thin-film transistors, light-emitting devices, and solar cells. The "soft" nature of these materials, as characterized by their low formation energy and Young's modulus, and high thermal expansion coefficients, not only enables thin films to be fabricated via low-temperature deposition methods but also presents rich opportunities for manipulating film formation. This comprehensive review explores how the unique chemistry of these materials can be exploited to tailor film growth processes and highlights the connections between processing methods and the resulting film characteristics. The discussion focuses principally on methylammonium lead iodide (CH 3 NH 3 PbI 3 or MAPbI 3 ), which serves as a useful and well-studied model system for examining the unique attributes of halide perovskites, but various other important members of this family are also considered. The resulting film properties are discussed in the context of the characteristics necessary for achieving high-performance optoelectronic devices and accurate measurement of physical properties.

Bismuth‐Based Perovskite‐Inspired Solar Cells: In Situ Diagnostics Reveal Similarities and Differences in the Film Formation of Bismuth‐ and Lead‐Based Films

“…To conclude, the CB dripping triggers the nucleation of the Bi‐compound phase. Antisolvent dripping, which extracts the solvent from the film during spinning within seconds, can induce rapid and uniform nucleation of the grains, thus preventing large grains from forming . In the GBL solvent, the textured film has started to form before dripping at 40 s. Thus, dripping at this specific time does not alter the crystalline texture.…”

Two‐Dimensional Halide Perovskites in Solar Cells: 2D or not 2D?

“…The perovskite structure can be adopted by an enormous number of A n + , B m + , and X n − combinations, giving rise to a vast diversity of properties . However, with regard to halide perovskites (where X=Cl, Br, or I), A is restricted to only a few small cations namely: Cs, Rb, K, Na, NH 4 , methylammonium (MA), and formamidinium (FA), as these are the only ones that form reasonably stable 3D phases; therefore, the number of possible compositions and structures is significantly reduced . In contrast, 2D perovskites are a vast family of materials that allow a greater diversity of compositions and properties.…”

“…Given their higher crystallinity and the fact that perovskite film formation is driven by the 2D nature of the materials, highly oriented 2D perovskite films are readily formed through one‐step spin‐coating processes contrary to their 3D counterparts, which usually render poor‐quality films if a single‐step method is used . In some cases, like the ones reported by Smith et al .…”

“…[8] However, with regard to halide perovskites (where X = Cl, Br,o rI ), Ai sr estricted to only af ew small cations namely:C s, Rb, K, Na, NH 4 ,m ethylammonium (MA), and formamidinium (FA), as these are the only ones that form reasonablys table 3D phases;t herefore, the number of possible compositions and structures is significantly reduced. [11] In contrast, 2D perovskites are av ast family of materials that allow ag reater diversity of compositions and properties. They can be seen as the dimensional reduction of the 3D perovskite lattice,w ith the general formula (A') m A nÀ1 B n X 3n + 1 ,w here A' can be am onovalent( m = 2) or divalent (m = 1) cation that intercalates betweent he inorganic A nÀ1 B n X 3n + 1 2D sheets (Scheme 1) and n can be understood as the thickness of the inorganic layers.…”

Two‐Terminal Perovskites Tandem Solar Cells: Recent Advances and Perspectives

“…Due to the strong optical absorption, long diffusion length distinguished compatibility, and tunability of broad bandgap, metal halide perovskites (ABX 3 ) have achieved rapidly increasing efficiencies and opened up a great potential to develop perovskite‐based tandem cells . Moreover, by taking advantages of cost‐effectiveness and facile solution processability, scalable processing methods for fabricating defect‐free and large‐scale perovskite films, such as antisolvent spraying, meniscus‐assisted solution printing (MASP), etc., further promote the development of perovskite‐based tandem cells. To date, most reported perovskite‐based tandem cells are based on perovskite–silicon (1.1 eV), perovskite–perovskite and perovskite–CIGS (1.02–1.68 eV) integrations …”