The simulation of quantum transport in nanodevices requires the solution of the Dyson and Keldysh equations, a task dominated by the inversion of massive, block-tridiagonal matrices. While the Recursive Green's Function (RGF) method has long been the standard O(N) solver for quasi-1D systems, its formulation has typically been restricted to sequential execution and nearest-neighbor interactions. In this work, we carefully reformulate RGF through the lens of Domain Decomposition and Schur Complement theory. This allows us to extend the recursive formalism to block n-diagonal systems (handling higher-order stencils) and to derive a parallel algorithm, Domain-Decomposition based RGF (DDRGF), which stitches macroscopic domains via reduced interface systems. We explore data dependencies in DDRGF in detail, by means of block-sparse structures and tracing back to the desired output as a block tridiagonal approximation, giving a clear, reproducible and extensible formulation. We validate these algorithms using , a Julia-based implementation, demonstrating that the structural insights of domain decomposition provide a robust pathway for high-performance quantum transport simulations on modern multi-core clusters. The theory presented here lays down the base for tackling the Keldysh problem, to be similarly handled in future stages of our work. Although the target here is the acceleration of kernels in the non-equilibrium Green's function method, the algorithms and the implementations presented can be immediately used in any application involving block n-diagonal systems.

Defect engineering in two-dimensional semiconductors has primarily focused on controlling the nature and concentration of atomic defects. Here, we show that the spatial arrangement of defects can be equally decisive in determining electronic transport. Using sulfur vacancies in monolayer MoS_2 as a model system, we investigate the impact of vacancy ordering through density functional theory, density functional tight-binding calculations, and quantum transport simulations. We demonstrate that a periodic vacancy arrangement at a concentration of 11.1

This study examines the optoelectronic properties of nitride‐based multiquantum well solar cells, which are gaining importance in hybrid thermal‐photovoltaic applications due to their resilience to high temperatures. The investigation focuses on the current characteristics of these devices under six distinct illumination conditions. A self‐consistent approach is employed, combining the drift‐diffusion semiclassical framework with a Green's function‐based method to account for quantum effects associated with the quantum well structures. This hybrid method enhances the accuracy of the optoelectronic property predictions, as demonstrated by comparisons with simulations using only the drift‐diffusion model. A detailed analysis of a specific simulation case, compared with the experimental measurements of the cells under real concentrated sunlight, further highlights the significance of quantum effects in these systems, validating the proposed methodology.

Bilayer nickel oxide (NiOx)/[2-(3,6-dimethoxy-9H-carbazol-9yl) ethyl] phosphonic acid (MeO-2PACz) hole transport layers have become attractive for perovskite solar cells and tandem architectures. However, challenges such as the instability of NiOx ink, hole accumulation, and trap-assisted non-radiative recombination at the interface remain major drawbacks for using NiOx/MeO-2PACz HTL bilayer. In this work, two synergic strategies are employed to address these issues such as the doping of the NiOx ink with niobium (Nb)-based MXene) and the introduction of S-benzyl-L-cysteine (SBLC) molecule to passivate the MeO-2PACz/perovskite interface. These modifications effectively reduced defect states in the perovskite layer and enhanced the dipole moment of MeO-2PACz, minimizing the valence band offset at the MeO-2PACz/perovskite interface with the reduction of the charge recombination rates. Consequently, the target PSC device, made of 1.68 eV-bandgap perovskite, demonstrated a power conversion efficiency (PCE) of 19.5% and improved stability compared to the control device when tested under ISOS protocols. Furthermore, semi-transparent (ST) PSCs have been fabricated for application in 4T tandem perovskite-silicon cell showing PCE of 18.15% and 27.95% in single-junction and in tandem architectures, respectively. These findings demonstrate the effectiveness of combining strategic doping and passivation techniques for inverted PSCs enhancing the device performance without discarding long-term stability.

We present a tight-binding description of mixed perovskites showing an application to Sn-Pb mixed systems. We discuss the parameterization procedure and the preliminary results obtained for $\text{MASn}_{0.5} ~\text{Pb}_{0.5} \mathrm{I}_{3}$. Our model shows a treatment of the band gap bowing observed for this perovskite alloy when Sn segregation is considered. Note that our method can be easily extended to include the description of all the perovskite crystal phases and more refined strain effects.

Graphynes, a class of two-dimensional carbon allotropes, exhibit exceptional electronic properties, similar to graphene, but with intrinsic band gaps, making them promising for semiconducting applications. The incorporation of acetylene linkages allows for systematic modulation of their properties. However, the theoretical characterization of graphynes remains computationally demanding, particularly for electron-phonon coupling (EPC) analyses. Here, we employ the density functional tight binding method within the DFTBEPHY framework, providing an efficient and accurate approach for computing EPC and transport properties. We investigate the structural, mechanical, electronic, and transport properties of graphynes, comparing transport calculations using the constant relaxation-time approximation and the self-energy relaxation-time approximation (SERTA) alongside analytical models based on parabolic- and Kane-band approximations. For graphyne, the SERTA relaxation time is 0.63 (1.69) ps for holes (electrons). In graphdiyne, the relaxation time is 0.04 (0.14) ps for holes (electrons). While the hole mobilities in graphyne are on the order of 103 cm2 V-1 s-1, the electron mobilities reach up to 104 cm2 V-1 s-1. In graphdiyne, the mobility values for both types of charge carriers are on the order of 102 cm2 V-1 s-1. The phonon-limited mobilities at room temperature in graphyne fall between those of graphene and MoS2, while in graphdiyne, they are comparable to those of MoS2.

The tedious parametrization process remains a key bottleneck hindering broader adoption of the empirical tight-binding method. Here, we discuss the challenges and requirements of finding parameters for Slater-Koster-based empirical tight-binding schemes, and explain the shortcomings of the parametrization procedures commonly used in the literature. We then propose our way to address these challenges, through the presentation of an open-sourced parametrization toolbox that breaks up the task into several, incremental stages. The prototype of our toolbox is tailored especially to deal with a recently proposed, highly transferable scheme, but can be easily adapted to any Slater-Koster-based scheme. A case study of fitting GaN parameters is considered. Remarkably, the obtained GaN parameter set shows high transferability when applied to various contexts: from simple zincblende or wurtzite bulk cases, to polytypic heterostructures and even highly mismatched alloys in their dilute limits. This confirms the effectiveness and robustness of our parametrization approach.

We analyze and present applications of a recently proposed empirical tight-binding scheme for investigating the effects of alloy disorder on various electronic and optical properties of semiconductor alloys, such as the band gap variation, the localization of charge carriers, and the optical transitions. The results for a typical antimony-containing III-V alloy, GaAsSb, show that the new scheme greatly improves the accuracy in reproducing the experimental alloy band gaps compared to other widely used schemes. The atomistic nature of the empirical tight-binding approach paired with a reliable parameterization enables more detailed physical insights into the effects of disorder in alloyed materials.

Empirical tight-binding (ETB) methods have become a common choice to simulate electronic and transport properties for systems composed of thousands of atoms. However, their performance is profoundly dependent on the way the empirical parameters were fitted, and the found parametrizations often exhibit poor transferability. In order to mitigate some of the the criticalities of this method, we introduce a novel Δ-learning scheme, called MLΔTB. After being trained on a custom data set composed of ab-initio band structures, the framework is able to correlate the local atomistic environment to a correction on the on-site ETB parameters, for each atom in the system. The converged algorithm is applied to simulate the electronic properties of random GaAsSb alloys, and displays remarkable agreement both with experimental and ab-initio test data. Some noteworthy characteristics of MLΔTB include the ability to be trained on few instances, to be applied on 3D supercells of arbitrary size, to be rotationally invariant, and to predict physical properties that are not exhibited by the training set.

Empirical tight-binding is a valuable and reliable tool for the calculation of electronic and optical properties in semiconductor heterostructures and alloys. It has been applied in many contexts, ranging from inorganic semiconductors like arsenides, antimonides, nitrides and their alloys to 2D materials and hybrid perovskites. Here we present recent activities in development and application of empirical tight-binding, in particular regarding disordered alloys. We show some limitations of the most used schemes, and how they can be overcome by more recent parameterizations, and we introduce an alternative machine-learning based parameterization scheme.

Poly Lactic Acid / Poly Butylene Adipate-co-Terephthalate blends are used as packaging green materials since they constitute hydrophilic and biodegradable plastic. With the aim of improving the mechanical characteristics of such blends as biodegradable packaging materials for food products the addition of starch has been considered. In silico test performed by classical molecular dynamics highlighted that the addition of starch can reinforce the polymeric structure via starch-polymer interactions, suggesting that starch can be a suitable material to be added to the Poly Lactic Acid / Poly Butylene Adipate-co-Terephthalate blend to obtain more resistant packaging materials. Experimental analysis of the mechanical properties of the polymeric blend containing different amounts of starch confirmed what foreseen by MD, highlighting an increase of Young modulus and glass transition as a function of added starch. The coupled theoretical/experimental approach constitutes added value of the present work, furnishing important data on the reinforcement of the packaging material performances and a molecule-based interpretation and comprehension of the observed phenomenon.

Optical nanoscale metrological techniques like Raman spectroscopy produce large amounts of data, especially if employed as a default characterisation tool in industrial production lines. Proper management of huge amounts of data is needed, in order to allow for their further use in data analysis, automatization or in machine learning applications. The definition of metadata and the design of the database structure are paramount in these contexts. This work presents the prototype development of such data management system, showcasing effective data and metadata management in compliance with EU defined standards for scientific research. The data handling of tip-enhanced Raman spectroscopy (TERS) measurements is used as a benchmark. Metadata and data format definitions as well as the database structure implementation are described.

Crystalline Bi4O4SeCl2 exhibits record-low 0.1 W/mK lattice thermal conductivity (κL), but the underlying transport mechanism is not yet understood. Using a theoretical framework which incorporates first-principles anharmonic lattice dynamics into a unified heat transport theory, we compute both the particle-like and glass-like components of κL in crystalline and pellet Bi4O4SeCl2 forms. The model includes intrinsic three- and four-phonon scattering processes and extrinsic defect and extended defect scattering contributing to the phonon lifetime, as well as temperature-dependent interatomic force constants linked to phonon frequency shifts and anharmonicity. Bi4O4SeCl2 displays strongly anisotropic complex crystal behavior with dominant glass-like transport along the cross-plane direction. The uncovered origin of κL underscores an intrinsic approach for designing extremely low κL materials.

A possible solution for the realization of high-efficiency visible light-emitting diodes (LEDs) exploits InGaN-quantum-dot-based active regions. However, the role of local composition fluctuations inside the quantum dots and their effect of the device characteristics have not yet been examined in sufficient detail. Here, we present numerical simulations of a quantum-dot structure restored from an experimental high-resolution transmission electron microscopy image. A single InGaN island with the size of ten nanometers and nonuniform indium content distribution is analyzed. A number of two- and three-dimensional models of the quantum dot are derived from the experimental image by a special numerical algorithm, which enables electromechanical, continuum k→·p→, and empirical tight-binding calculations, including emission spectra prediction. Effectiveness of continuous and atomistic approaches are compared, and the impact of InGaN composition fluctuations on the ground-state electron and hole wave functions and quantum dot emission spectrum is analyzed in detail. Finally, comparison of the predicted spectrum with the experimental one is performed to assess the applicability of various simulation approaches.

Simulation of electronic devices relies to large extent on semi-classical models, especially the drift-diffusion model. Where quantum effects or atomistic details are particularly important, more involved models are used. Ideally, a combination of models on different scales would allow the simulation of the overall device structure. Here we present some approaches for combining continuum and atomistic models with the drift-diffusion model for the simulation of optoelectronic devices.

We theoretically study the direct gap and the band-edge wavefunctions’ localization of nonuniform disordered GaAsSb alloy by using empirical tight-binding simulations. We show that the nonuniformity decreases the direct gap value of the alloy while increases its statistical scattering, leading to a larger bandgap bowing compared to the ideal random alloy case. Moreover, the localization of the band-edge hole wavefunction is also enhanced due to the nonuniformity, while the band-edge electron does not experience similar effect.

The calculation of the electron–phonon coupling from first principles is computationally very challenging and remains mostly out of reach for systems with a large number of atoms. Semi-empirical methods, like density functional tight binding (DFTB), provide a framework for obtaining quantitative results at moderate computational costs. Herein, we present a new method based on the DFTB approach for computing electron–phonon couplings and relaxation times. It interfaces with phonopy for vibrational modes and dftb+ to calculate transport properties. We derive the electron–phonon coupling within a non-orthogonal tight-binding framework and apply them to graphene as a test case.

AbstractUsing a density functional theory‐based thermal transport model, which includes the effects of temperature (T)‐dependent potential energy surface, lattice thermal expansion, force constant renormalization, and higher‐order quartic phonon scattering processes, it is found that the recently synthesized nitride perovskite LaWN3 displays strong anharmonic lattice dynamics manifested into a low lattice thermal conductivity (κL) and a non‐standard κL∝T−0.491 dependence. At high T, the departure from the standard κL∝T−1 law originates in the dual particle‐wave behavior of the heat carrying phonons, which includes vibrations tied to the N atoms. While the room temperature κL=2.98 W mK‐1 arises mainly from the conventional particle‐like propagation of phonons, there is also a significant atypical wave‐like phonon tunneling effect, leading to a 20% glass‐like heat transport contribution. The phonon broadening effect lowers the particle‐like contribution but increases the glass‐like one. Upon T increase, the glass‐like contribution increases and dominates above T = 850 K. Overall, the low κL with a weak T‐dependence points to a new utility for LaWN3 in energy technology applications, and motivates synthesis and exploration of nitride perovskites.

Although isolated nonhexagonal carbon rings in graphene are associated with strain relaxation and curvature, dense and ordered arrangements of four‐, five‐, and eight‐membered rings with strained carbon–carbon bonds can tile 2D planar layers. Using the Boltzmann transport equation formalism in combination with density functional theory calculations, how the presence of nonhexagonal rings impacts the thermal conductivity of three 2D carbon allotropes: T‐graphene (four and eight rings), biphenylene (four, six, and eight rings), and net‐graphene (four, six, and eight rings), is investigated. The phonon thermal conductivity (κph), which captures three‐phonon, four‐phonon, and phonon–electron interactions, is significantly lowered with respect to pristine graphene. In compensation, the electron thermal conductivity (κe), which captures electron–phonon interactions, is enhanced to record high values, such that the room‐temperature total thermal conductivity κtotal = κph + κe approaches the values of pristine graphene. 2D carbon allotropes could be of interest for applications requiring thermal energy transfer by a combination of diffusion of electrons and phonon vibrations.