Synthetic approaches for thin-film halide double perovskites

Abstract

Inspired by the fascinating class of hybrid organic-inorganic halide perovskite materials, halide double perovskites have emerged as non-toxic Pb-free contender for the application as active layers in optoelectronic devices. Heterovalent substitution of Pb 2+ by non-toxic metal cations yield the double perovskite structure which allows for compositional flexibility. In fact, the compositional space is large given that multiple cations and halides can be combined resulting in >10 6 perovskite combinations. A starkly increasing number of stable halide double perovskite compositions are theoretically predicted. The synthesis however, lacks behind and many double perovskites are primarily synthesized as powder samples instead of thin films. The latter however, are needed for thin film devices such as solar cells, light-emitting devices, and thin film transistors. When comparing the synthetic approaches successfully applied to hybrid perovskites to methods used for the fabrication of double perovskites, the latter is clearly in its very infancy. The question is whether solution engineering and compositional modification strategies can be exploited to match the exceptional optoelectronic properties of hybrid perovskites. This review is motivated by a text mining effort that not only illustrates the prevalence of powder over thin film synthesis but also the discrepancy between the number of compositions experimentally realized and studied as compared to the many predicted compositions. Here we summarize the synthesis aspects of halide double perovskites, and in particular of thin films, including deposition techniques and synthetic modifications to alter film properties.

Impact of processing conditions on the film formation of lead-free halide double perovskite Cs2AgBiBr6

“…Halide double perovskite synthesis methods were delineated into four categories: crystal synthesis using (1) a solution or (2) a solid-state route, and thin film synthesis using (3) solution or (4) vapor deposition, similar to the text-mined synthesis breakdown in Zhao et al 8 In addition to all of the Cs 2 AgBiBr 6 synthesis articles extracted through the methods above, all remaining relevant publications were found by querying Clarivate Web of Science for articles containing the topic “Cs 2 AgBiBr 6 ”. The synthesis method used in each article was determined manually.…”

“…Statistics on the body of synthesized halide double perovskites were extracted through a combination of automated and manual text processing techniques, similar to the methods for text mining discussed in Zhao et al 8 To facilitate automated text extraction, we leveraged article data from a collection of full-text papers mined by the Ceder Group (with years ranging from 2000-2020) and abstracts from MatScholar (with years ranging from 1900-2018). 30,31 Articles from these databases were ltered through a keyword search for "perovskite(s)".…”

“…[36][37][38][39][40][41][42][43][44] The large share of Cs 2 AgBiBr 6 in experimental publications is probably due to the ease of processability of Cs 2 AgBiBr 6 from solutions due to the relatively good solubility of Cs 2 AgBiBr 6 precursors as compared to other halide double perovskite compounds. 7,8 Fig. 1b shows the distribution of the most used processing techniques to synthesize Cs 2 AgBiBr 6 out of 155 experimental publications.…”

“…[5][6][7] These halide double perovskites adapt a crystal lattice with general formula A 2 B + B 03+ X 6 or A 2 B 4+ X 6 (A is a monovalent cation, B + , B 03+ , and B 4+ are monovalent, trivalent, and tetravalent metal cations, respectively, and X is a halide anion), corresponding to mixed mono-plus trivalent-metal double perovskites or tetravalent-metal vacancy ordered double perovskites, respectively. 7,8 Amongst different halide double perovskites, Cs 2 AgBiBr 6 has shown attractive optoelectronic properties and stability, making it a promising candidate for stable high-efficiency optoelectronic devices. [9][10][11][12][13][14] Although the synthesis of Cs 2 AgBiBr 6 has been successfully demonstrated via solution processing methods, [9][10][11][12][13][14] mechanistic insights on the thin lm formation process are lacking.…”

Lead-free all-inorganic halide double perovskite materials for optoelectronic applications: progress, performance and design

“…19,[32][33][34] The three-dimensional cubic structure of these LFAIHDPs is similar to that of Pb-based compounds. 35,36 Also, different monovalent cations have been tested to tune their optoelectronic properties. In addition, LFAIHDPs with the chemical formula of Cs 4 M(II)M(III) 2 X 12 [M(II) = Ca 2+ , Cu 2+ , etc.…”