The energy sustainability across the information technology is challenged by increasing demand. It is of paramount importance to make computing more energy efficient, and among the many components, transistors seem to be the best starting point. Recently, tunnel field effect transistors (TFETs) have been proposed as promising candidates for low-power applications and would enable not only the down-scaling power consumption in modern and future computing, but also faster transistors capable of supporting the ever-growing requirements for data-rate transmission. The overall objective of this project is to provide fundamental insights into the electronic and transport properties of heterojunctions and van der Waals heterostructures, in order to establish guidelines for the development of next generation 2D-based TFETs. Density functional theory (DFT) and related methods will be used to first determine low-strain interface models for various heterostructures. Promising 2D materials like group-IV and group-V single-layers (e.g. graphene, phosphorene, arsenene) and TMD monolayers (MoS2, WS2, WSe2 …) will be considered. Interface models will be used to determine band alignments at the 3D/2D interfaces and across 2D heterostructures. The calculations will be carried out using for instance recent developments in constructing dielectric-dependent hybrid functional which accurately describes the electronic properties of heterogeneous interfaces. Furthermore, the role of defects will be investigated, since dangling bonds or other electronic interface states can affect properties of devices. To properly quantify the performance of ultra-scaled devices with channel lengths below 100 nm, a complete quantum mechanical description of the electron transport is required. Combining DFT with the non equilibrium Green’s function method (NEGF) has been the most efficient and widely used approach to study transport through nanoscale devices. The transport properties of the heterostructures will be evaluated by computing both the I-V characteristics and the transmission spectra. The I-V characteristics of the pristine and defective systems will be compared, to evaluate the impact of defects on the device performance.