F. Anselm Rasmussen, K. Sommer ThygesenWe present a comprehensive first-principles study of the electronic structure of 51 semiconducting monolayer transition metal dichalcogenides and -oxides in the 2H and 1T hexagonal phases. The quasiparticle (QP) band structures with spin-orbit coupling are calculated in the G0W0 approximation and comparison is made with different density functional theory (DFT) descriptions. Pitfalls related to the convergence of GW calculations for 2D materials are discussed together with possible solutions. The monolayer band edge positions relative to vacuum are used to estimate the band alignment at various heterostructure interfaces. The sensitivity of the band structures to the inplane lattice constant is analysed and rationalized in terms of the electronic structure. Finally, the q-dependent dielectric functions and effective electron/hole masses are obtained from the QP band structure and used as input to a 2D hydrogenic model to estimate exciton binding energies.Filip Anselm Rasmussen is working as a PhD student at the Center for Nanostructured Graphene (CNG) and Center for Atomic Scale Materials Design (CAMd) at the Department of Physics at the Technical University of Denmark under the supervision of Professor Kristian Thygesen. His work aims at calculating the electronic excitations of novel 2D materials using computational first principles methods.