Highly Stable New Organic-Inorganic Hybrid 3D Perovskite CH3NH3PdI3 and 2D Perovskite (CH3NH3)3Pd2I7: DFT Analysis, Synthesis, Structure, Transition Behavior, and Physical Properties.

The feasibility of Pd-based organic-inorganic hybrid perovskites is comprehensively explored with both theoretical and experimental methods for the first time. Experimentally, the new 3D perovskite CH3NH3PdI3 (tetragonal, I4 cm) can be transited to a new 2D perovskite (CH3NH3)3Pd2I7 (tetragonal, P4 mm) by modulating the ratio of the organic part to inorganic part. The structure, lattice parameters, and symmetry of these two perovskites are verified by a series of simulations, refinement, and characterizations. The basic optical and electronic properties of these two new perovskites are characterized and calculated with DFT for future applications. Interestingly, both types of perovskites exhibit long stability in air with 50% relative humidity. Two-day stability for the 3D perovskite and one-week stability for the 2D perovskite are observed, consistent with our DFT calculation that 2D perovskite (CH3NH3)3Pd2I7 is more energetically stable than 3D hybrid perovskite CH3NH3PdI3.