Molecular Intercalation and Electronic Two Dimensionality in Layered Hybrid Perovskites

In layered hybrid perovskites, such as (BA)₂ PbI₄ (BA=C₄ H₉ NH₃ ), electrons and holes are considered to be confined in atomically thin two dimensional (2D) Pb-I inorganic layers. These inorganic layers are electronically isolated from each other in the third dimension by the insulating organic layers. Herein we report our experimental findings that suggest the presence of electronic interaction between the inorganic layers in some parts of the single crystals. The extent of this interaction is reversibly tuned by intercalation of organic and inorganic molecules in the layered perovskite single crystals. Consequently, optical absorption and emission properties switch reversibly with intercalation. Furthermore, increasing the distance between inorganic layers by increasing the length of the organic spacer cations systematically decreases these electronic interactions. This finding that the parts of the layered hybrid perovskites are not strictly electronically 2D is critical for understanding the electronic, optical, and optoelectronic properties of these technologically important materials.