From 1D to 3D: Perovskites within the System HSC(NH2)2I/CH3NH3I/PbI2 with Maintenance of the Cubic Closest Packing

This work describes crystalline phases of the system [HSC(NH2)(2)]I/(CH3 NH3)I/PbI2 and discusses the crystal structures in the context of a common cubic closest packing of organic cations and iodide anions with Pb2+ in all anionic octahedral voids. Ternary boundary phases were (CH3NH3)PbI3 (3D perovskite), [HSC(NH2)(2)](3)PbI5 (1D perovskite), [HSC-(NH2)(2)]PbI3 (NH4CdCl3 type), and [HSC(NH2)(2)]Pb2I5, with strands of edge-sharing octahedra of the NH4CdCl3 type, which are connected to 2D layers via common corners. Within the system, we identified ribbonlike structures of the general composition [HSC(NH2)(2)](m+1) (CH3NH3)(m)PbmI4m+1 with m = 2 and 3, representing the transition from 1D to 2D structures. Layered structures with variable thickness were found for the series [HSC(NH2)(2) ](CH3NH3),PbnI3n+1 with n = 1-3. The color and band gap correlate directly with the pattern of how the PbI6 octahedra are linked. 1D structures are colorless or pale yellow to orange. Layered structures are red to black, depending on the layer thickness. A first laboratory-scale solar cell yielded an efficiency of similar to 6% based on the compound with n = 3.

Automated summary

This study describes the crystalline phases of the [HSC(NH2)(2)]I/(CH3NH3)I/PbI2 system and discusses the crystal structures within the context of a common cubic closest packing of organic cations and iodide anions with Pb2+ in all anionic octahedral voids. Various ternary boundary phases were identified, with color and band gap correlating directly with the pattern of how the PbI6 octahedra are linked. The efficiency of a laboratory-scale solar cell using the compound with n = 3 reached approximately 6%.