Investigation on structure-property relationships of 2D Ga/In chalcogenides

This work is about the theoretical investigation on structural, electronic, and optical properties of bulk, mono-, bi-, and trilayered MX (M=Ga, In; X=S, Se, Te) and GaX/InX heterostructures by using DFT calculations. By varying the layer thickness and stacking order, the structure-property relationship for vdW homo- and heterostructures have been studied. The widespreading bandgaps, high absorption coefficients and conversion efficiency prove the applicability of 2D vdW GaX and InX materials in photovoltaic devices. According to the quantum theory of atoms in molecules, topological analyses become possible by partionning the real space into basins with each basin having one nucleus. Based on the distributions of electron density and its Laplacian, the evolution of bond degree, bond length and bond angle can be obtained. Thus, the whole picture of interatomic interations provides the chance for connecting the microscopic interactions with microscopic electromagnetic behaviors. The inversely correlated bond degree summation and static dielectric constant suggest that through bonding enginnering, it is possible to achieve equivalent optical response with the bulks but with fewer materials. Reasons for vdW heterostructures free of lattice constraints and the exclusively distributed electrons and holes in their sublayers are given from the topological point of view.