Colloidal Synthesis of Single-Layer Quasi-Ruddlesden–Popper Phase Bismuth-Based Two-Dimensional Perovskite Nanosheets with Controllable Optoelectronic Properties

Abstract

Single- and few-layered two-dimensional (2D) nanomaterials have attracted intense research interest in the last two decades due to their unique electronic and optoelectronic properties leading to various potential applications. Herein, we report the colloidal synthesis of Bi-based 2D perovskite nanosheets (PEG6-NH3 +) n Cs3–n Bi2X9, where X = Cl, Br, and I, through careful design of reaction conditions and selection of poly­(ethylene glycol) (PEG6) surface passivating ligands. The 2D nanosheets are ∼5 nm in thickness with micron-sized lateral dimensions and display composition-dependent band gap and work function modulation. Small-angle X-ray scattering analysis substantiates that the individual inorganic crystal layer, Cs3–n Bi2X9, is separated by the spacer, PEG6 ligand. Additionally, we determined that PEG6-NH2 is an essential passivating ligand and spacer for the formation of Bi-based 2D nanosheets. Most importantly, controlled crystallization of the colloidal dispersion of nanosheets results in the formation of superlattice microstructures of the quasi-Ruddlesden–Popper phase. These microstructures can be exfoliated to ultrathin nanosheets by overcoming the van der Waals interaction between the organic passivating layers. The controlled synthesis of lead-free 2D perovskite nanosheets presented here can expand their utility to photocatalytic and optoelectronic applications with reduced toxicity.

Metal–Halide Perovskite Nanocrystal Superlattice: Self‐Assembly and Optical Fingerprints

“…Fine structure analysis showed that as the number of acid ligands increased, layered structures gradually emerged, which were quite similar to those in 2D layered hybrid perovskite materials (Figure 4f ). [72][73][74][75][76] The distance between layers was then identified as 2 times the ligand length, indicating a Ruddlesden-Popper configuration. [77] In addition, the TOPO-mediated one-step approach proved effective for the formation of 2D nanoplatelets and superlattices using FAPbBr 3 (FA = formamidine).…”

Silver Ions Assisted Inversion Temperature Crystallization of 2D Cs3Bi2Br9 Nanoflakes for Highly Sensitive X‐Ray Detection

“…We have also investigated related work about synthesis of 2D Cs 3 Bi 2 Br 9 nanoflakes, including the hot injection method, [20] the antisolvent recrystallization method [21] and the wet-chemical method. [39] However, the hot injection method is effective for synthesizing Cs 3 Bi 2 Br 9 quantum dots with sizes smaller than 10 nm; the in-plane size of Cs 3 Bi 2 Br 9 prepared by antisolvent recrystallization method is about 200 nm, which is still too small for device application; the wet-chemical method could synthesize Cs 3 Bi 2 Br 9 with about 10 μm in-plane size, but the thickness is about 500 nm and unevenly distributed.…”

“…[15][16][17][18] As a typical A 3 B 2 X 9 structure, 2D Cs 3 Bi 2 Br 9 possesses ideal electronic structure, direct bandgap, long carrier diffusion length and high light absorption, rendering it an excellent candidate for applications in photodetectors, solar cells and light-emitting diodes. [19][20][21][22] Combined with large effective atomic number, high resistivity (10 7 -10 12 Ω cm) and high density (4.7 g cm −3 ), 2D Cs 3 Bi 2 Br 9 has been widely applied to detect X-ray. [23][24][25] Furthermore, large-size 2D Cs 3 Bi 2 Br 9 nanoflakes not only have lower bulk defects, higher carrier mobility and longer carrier lifetime, allowing for the excited electrons or holes to drift the device channel quickly, but also is compatible with integrated X-ray detectors.…”

Solvent-mediated crystallization of (TMS)2BiBr5·DMSO: a new 0D hybrid halide perovskite

“…Various types of perovskite structures such as three-dimensional (3D), 27,28 two-dimensional (2D), [29][30][31][32][33] one-dimensional (1D), 34,35 and zero-dimensional (0D) 36 can be realized by choosing appropriate components of the organometal halide perovskites owing to the structural tunability of these HHPs. For 0D hybrid perovskites, individual metal halide octahedra anions or metal halide clusters are completely surrounded and isolated by the organic cations.…”