OPTEL2D: Opto-electronic properties of 2D Transition Metal Dichalcogenides with DFT and post-DFT simulations

Our Prace research project OPTEL2D

“Opto-electronic properties of 2D Transition Metal Dichalcogenides with DFT and post-DFT simulations”

has been accepted, and we got 49.5 million core hours on Marconi – KNL.



Here the project description:
“Two-dimensional (2D) and layered materials possess novel combinations of electronic and optical properties and thus present a unique opportunity in condensed matter research and semiconductor devices. If experimental techniques to grow 2D materials on large areas, continue advancing, the new properties of these materials may enable a paradigm shift in semiconductor-based technologies leading to flexible and ultrathin next-generation electronic and opto-electronic devices. First-principles methods are playing an important role in the scientific development of this research area. Calculations can nowadays synergically complement experiments and greatly help the microscopic interpretation of physical processes, as well predict novel properties and new 2D materials. Generally speaking, 2D materials possess physical properties that are very different from conventional bulk materials, including a high sensitivity to defects and impurities, molecular functionalization, weak dielectric screening and strong light-matter interaction. In particular, the reduced dimensionality results in striking many-body effects such as gigantic transport gap renormalization and strongly bound but spatially delocalized excitons. From a theoretical/computational point of view this means that it is important to overcome the mean-field density functional theory (DFT) framework and to use post-DFT approaches, based on many-body perturbation theory (namely GW and BSE methods) in order to obtain an accurate knowledge of their electronic and optical excitations. Although graphene is still the king of the 2D realm, the absence of an intrinsic gap is problematic for several applications and the scientific attention over the world is now focusing on novel 2D materials with sizable band-gap such as the family of transition metal dichalcogenides. They have strong light-matter interaction and mobilities similar to bulk semiconductors, coupled to a robust air stability. While multi-layers have a very negligible light emission, monolayers emit light due to their direct gap. Moreover it has been shown that TMD/TMD or TMD/graphene hetero-junctions can achieve ultrahigh power densities in ultra-thin PV cells [see PI CV]. In this regard it is timely to understand how to improve the Quantum Yield (QY) of ML which, at the moment, is too low to be used in real light-emitting devices and also to study how to increase the photovoltaic efficiency in TMD heterostructures. The OPTEL2D project aims at achieving a systematic and coherent study by means of DFT and post-DFT simulations of several TMD materials. The main objectives are: i) to unveil the role of many-body effects of pristine group-VI Hexagonal-TMD with the main focus on the calculation of radiative lifetimes as well as on the analysis of fine-structure of the exciton series (dark and bright) by means of non-linear optical spectra calculations with a non-perturbative inclusion of spin-orbit interaction. ii) to investigate how many-body effects modify the opto-electronic properties of orthorombic ZT-phase of TMD and in particular to focus on the possible presence of excitonic instabilities iii) to reveal the role of atomic and molecular doping in the modulation of the opto-electronic properties of TMD monolayers iv) to engineering the opto-electronic properties of TMD heterostructures by mixing monolayers of different atomic structural phase.”

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