Inorganic-Cation Pseudohalide 2D Cs2Pb(SCN)2Br2 Perovskite Single Crystal

Most of the reported 2D Ruddlesden-Popper (RP) lead halide perovskites with the general formula of A(n)(+1)B(n)X(3)(n)(+1) (n = 1, 2, horizontal ellipsis ) 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, Cs2Pb(SCN)(2)Br-2, 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 angstrom) between the perovskite layers. The SCN- anions are found to bend the 2D Pb(SCN)(2)Br-2 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 CsPbBr3 (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 Cs2Pb(SCN)(2)Br-2-single-crystal photodetector is demonstrated with respectable responsivity of 8.46 mA W-1 and detectivity of approximate to 1.2 x 10(10) Jones at a low bias voltage of 0.5 V.

Automated summary

The first inorganic-cation pseudohalide 2D phase perovskite single crystal Cs2Pb(SCN)(2)Br-2 is reported in this study, synthesized by the antisolvent vapor-assisted crystallization method at room temperature. This 2D single crystal exhibits a low exciton binding energy and demonstrates respectable responsivity and detectivity at low bias voltage.