Inorganic-Cation Pseudohalide 2D Cs<sub>2</sub> Pb(SCN)<sub>2</sub> Br<sub>2</sub> Perovskite Single Crystal.
basic_science · Level V
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- Record sourced from PubMed, PMID 34866252.
- Also identified by DOI 10.1002/adma.202104782.
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Abstract
Most of the reported 2D Ruddlesden-Popper (RP) lead halide perovskites with the general formula of A<sub>n</sub> <sub>+1</sub> B<sub>n</sub> X<sub>3</sub> <sub>n</sub> <sub>+1</sub> (n = 1, 2, …) comprise layered perovskites separated by A-site-substituted organic spacers. To date, only a small number of X-site-substituted RP perovskites have been reported. Herein, the first inorganic-cation pseudohalide 2D phase perovskite single crystal, Cs<sub>2</sub> Pb(SCN)<sub>2</sub> Br<sub>2</sub> , is reported. It is synthesized by the antisolvent vapor-assisted crystallization (AVC) method at room temperature. It exhibits a standard single-layer (n = 1) Ruddlesden-Popper structure described in space group of Pmmn (#59) and has a small separation (d = 1.69 Å) between the perovskite layers. The SCN<sup>-</sup> anions are found to bend the 2D Pb(SCN)<sub>2</sub> Br<sub>2</sub> framework slightly into a kite-shaped octahedron, limiting the formation of a quasi-2D perovskite structure (n > 1). This 2D single crystal exhibits a reversible first-order phase transformation to 3D CsPbBr<sub>3</sub> (Pm3m #221) at 450 K. It has a low exciton binding energy of 160 meV-one of the lowest for 2D perovskites (n = 1). A Cs<sub>2</sub> Pb(SCN)<sub>2</sub> Br<sub>2</sub> -single-crystal photodetector is demonstrated with respectable responsivity of 8.46 mA W<sup>-1</sup> and detectivity of ≈1.2 × 10<sup>10</sup> Jones at a low bias voltage of 0.5 V.