arXiv subjects

A. C. Dias

Publications and source records attributed to A. C. Dias.

3 recordsLinked to original sources

arXiv2026

Chalcogen Impurity Barriers in 2D Systems via Semi-Empirical/Machine Learning Modeling: A Survey over 4000 Materials

Adequate characterization of two-dimensional materials with low energy barriers for impurity adsorption is key for advancing applications based on catalysis, sensing, and surface functionalization. However, first-principles methods, such as DFT, are often computationally extremely expensive for feasible large-scale screenings. Given such a scenario, we address a data-driven approach which integrates the semi-empirical Extended Huckel Method with machine learning techniques to estimate adsorption energy barriers in the case of three relevant chalcogen impurities, S, Se and Te. With this aim, we consider the 4036 2D materials found in the C2DB. The scheme employs the EHM to compute energy profiles along three in-plane migration paths, from which average barriers can be derived. The equilibrium distance between the impurity and the 2D surface is not calculated from a tie-consuming geometry optimization. Instead, it is estimated from a simple effective phenomenological expression. Physicochemical descriptors are then obtained from the Matminer library for curated features. Four different ML models are tested, with the XGBoost leading to the highest performance. We further use SHAP to verify the resulting predictions, focusing on the $\sim1,500$ materials displaying the lowest barrier values. As it could be anticipated, we establish that the average valence electron count, electronegativity, and atomic number are typically the most relevant attributes to validate the ML model. But we also are able to determine, for the different chalcogen atoms, which other few descriptors likewise considerably influence the adsorption properties. Our results show that when combined with interpretable ML protocols, EHM can produce a scalable framework for choosing 2D structures that exhibit the desired capture/release dynamics pertinent in a variety of utilization.

cond-mat.mtrl-sci↗

arXiv2025

Optical properties of TiS$_3$ as a novel thin film for single-junction and tandem solar cells

Sub-micrometer thin films are promising platforms for emerging flexible photovoltaic devices. Although the current market already produces efficient solar cells, the average wafer thickness of these devices remains far from the sub-micrometer scale, making them susceptible to cracking under bending stress and thus precluding their use in flexible device applications. Due to its earth abundance, non-toxicity, and low elastic modulus, titanium trisulfide (TiS$_3$) has emerged as a promising alternative for flexible device applications. Here, using excited-state density functional calculations combined with the transfer matrix approach, we perform an optical analysis and assess the efficiency of a prototype photovoltaic device based on sub-micrometer TiS$_3$ thin films. Using optical constants obtained from our first-principles calculations, we evaluate the photovoltaic response of a single-junction device in the radiative limit, finding that a 140-nm-thick active layer achieves a maximum power conversion efficiency of approximately 22%. Additionally, we investigate tandem solar cells that incorporate TiS$_3$ into perovskite thin films, and find that the lower and upper power conversion efficiencies range from approximately 18% to 33%. Overall, our results suggest great potential for using TiS$_3$ thin films as an active layer in the design of highly efficient flexible solar cells.

cond-mat.mtrl-sci↗

arXiv2024

Signature of excitonic insulators in phosphorene nanoribbons

Phosphorene is a recently developed two-dimensional (2D) material that has attracted tremendous attention because of its unique anisotropic optical properties and quasi-one-dimensional (1D) excitons. We use first-principles calculations combined with the maximally localized Wannier function tight binding Hamiltonian (MLWF-TB) and Bethe-Salpeter equation (BSE) formalism to investigate quasiparticle effects of 2D and quasi-1D blue and black phosphorene nanoribbons. Our electronic structure calculations shows that both blue and black monolayered phases are semiconductors. On the other hand black phosphorene zigzag nanoribbons are metallic. Similar behavior is found for very thin blue phosphorene zig-zag and armchair nanoribbon. As a general behavior, the exciton binding energy decreases as the ribbon width increases, which highlights the importance of quantum confinement effects. The solution of the BSE shows that the blue phosphorene monolayer has an exciton binding energy four times higher than that of the black phosphorene counterpart. Furthermore, both monolayers show a different linear optical response with respect to light polarization, as black phosphorene is highly anisotropic. We find a similar, but less pronounced, optical anisotropy for blue phosphorene monolayer, caused exclusively by the quasi-particle effects. Finally, we show that some of the investigated nanoribbons show a spin-triplet excitonic insulator behavior, thus revealing exciting features of these nanoribbons and therefore provides important advances in the understanding of quasi-one dimensional phosphorus-based materials.

cond-mat.mtrl-sci↗