Structural and thermodynamic limits of layer thickness in 2D halide perovskites

Authors: Chan Myae Myae Soe, G. P. Nagabhushana, Radha Shivaramaiah, Hsinhan Tsai, Wanyi Nie, Jean‐Christophe Blancon, Ferdinand S. Melkonyan, Duyen H. Cao, Boubacar Traoré, Laurent Pédesseau, Mikaël Képénékian, Claudine Katan, Jacky Even, Tobin J. Marks, Alexandra Navrotsky, Aditya D. Mohite, Constantinos C. Stoumpos, Mercouri G. Kanatzidis - Proceedings of the National Academy of Sciences, PNAS 2018 cited by 351

Significance Organic–inorganic hybrid perovskites are exciting new solar cell materials. In 2D perovskites, the 3D structure is spatially interrupted by a layer of intercalated ions, which may alter both stability and functionality. A major question concerns the limit to which the 2D architecture can be maintained as the thickness of the layers increases. A combination of synthetic chemistry, crystallography, and spectroscopy was used to obtain and identify the thickest 2D halide perovskite characterized to date, having seven layers. Experimentally measured enthalpies of formation as a function of layer thickness show systematic behavior and that higher homologues are energetically unstable, placing a limit on the number of layers possible in a single-phase 2D perovskite. Their application in photovoltaics is discussed.