Photoconductivity Switching in Semiconducting Two-Dimensional Crystals via Molecular Tetris

Abstract

Two-dimensional organic materials are mainly constructed by using orthogonal anisotropic connectivity of covalent bonding and π–π stacking. The noncovalent connectivity between building blocks is presumed to be too delicate to stabilize the two-dimensional (2D) layers. Contrary to this assumption, we constructed graphite-like 2D layered material by utilizing pure noncovalent connectivity, i.e., weak intermolecular and π–π interaction via a molecular Tetris strategy. We produce X-ray mountable single crystals comprising polycyclic aromatic heterocycles by employing a single-crystal-to-dissolution-to-single-crystal transformation methodology. The macromechanical analysis of this layered crystal shows shearing behavior, which is quantified using nanoindentation experiments. The 2D lattice’s layer space allows reversible intercalation–deintercalation of iodine, which enhances the photoconductivity by 17 folds. Combined efforts of X-ray diffraction, solid-state spectroscopy, and electrochemical studies established the mechanism of intercalation and resulting photoconductivity enhancement.