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Metal-ligand cluster ions are structurally characterized by means of gas-phase infrared multiple photon dissociation (IRMPD) spectroscopy. The mass-selected complexes consist of one or two metal cations M 3+ and two to five anionic bidentate acetylacetonate ligands. This study on simple species allows us to build some methodology benchmarks for further spectroscopic experiments and DFT calculations focused on larger model systems such as real liganded nanoparticles, as used by biochemists. In this context, we have studied three different metal ions (M = Al, Fe or Ru) and the experimental IR spectra were compared with different density functional theory (DFT) calculations, namely PBE/TZVP, B3LYP/6-31G* and M06/6-31+G**. Frequency analysis was also performed at different levels, namely scaled static harmonic, unscaled static anharmonic or with ab initio molecular dynamics simulations at the PBE/TZVP level. All methods lead to simulated spectra that fit rather well with experimental data, and the calculated data indicate that several bands of the spectra are sensitive to the strength of the metal-ligand interaction and to the spin state of the ion. Due to the rigidity of the complexes, first principles molecular dynamics calculations provide spectra similar to that produced by static calculations which are already able to catch these spectral signatures using harmonic calculations at the B3LYP/6-31G* level.

37th European Photovoltaic Solar Energy Conference and Exhibition; 618-620, In this study, photon recycling mechanisms in single junction thin-film GaAs solar cells are investigated. An approach of theoretical modeling supported by experimentally obtained results is used in order to correlate the reflectance of the cell's rear layers, the photon recycling probability and the solar cell performance. Solar cells with different top and bottom metallization configurations are produced and their performance is optically and electrically analyzed. It is shown that the photon recycling probability increases with the rear mirror reflectance and solar cell thickness, which results in the increase of the devices open circuit voltage. We identify the front grid coverage, which is usually disregarded in rear mirror focused studies, to be strongly reducing the photon recycling probability of the devices. Furthermore, based on preliminary calculations, the internal radiative efficiency of the solar cells seems to prevent further increase of the devices' open circuit voltage as a result of improvements to the rear mirror of the cells. In order to achieve a significant benefit of the increased photon recycling probability to the solar cell performance, the limiting mechanisms hindering the cells internal radiative efficiency need to be identified and properly addressed.

CIES2020 - XVII Congresso Ibérico e XIII Congresso Ibero-americano de Energia Solar RESUMEN: Los cuadernos abiertos (Open Notebooks), como los que pueden realizarse en el entorno Jupyter, son una herramienta excelente, no solo para documentar los programas que se implementan para realizar tal o cual cálculo, sino también para: a) facilitar la docencia sobre el asunto de que se trate, b) facilitar que terceros verifiquen con facilidad los cálculos realizados, c) posibilitar el cálculo interactivo. En el contexto del proyecto Europeo GRECO, dedicado al desarrollo de la ciencia e innovación responsable (RRI) aplicado al campo de la energía solar fotovoltaica, estamos desarrollando un “Open Notebook” para modelar analíticamente la denominada “célula solar de tres terminales de tipo transistor bipolar de heterounión”. En este trabajo describimos cómo acceder a dicho cuaderno, describimos el modelo utilizado para modelar dicha célula y comentamos algunas de las lecciones aprendidas en relación con su uso y el desarrollo de la ciencia abierta. ABSTRACT: Open Notebooks, such as those that can be made in the Jupyter environment, are an excellent tool, not only to document the codes that are implemented to perform this or that calculation, but also to: a) facilitate teaching on the subject in question, b) facilitate third parties to easily verify the calculations performed, c) enable interactive calculation. In the context of the European GRECO project, dedicated to the development of responsible research and innovation (RRI) in the field of photovoltaics, we are developing an “Open Notebook” to analytically model the so-called “three terminal heterojunction bipolar transistor solar cell”. In this paper, we describe how to access this Open Notebook, describe the model used to model said cell, and comment on some of the lessons learned in relation to its use and the development of open science. info:eu-repo/semantics/publishedVersion

36th European Photovoltaic Solar Energy Conference and Exhibition; 1543-1545, The effect of particle irradiation on the performance of GaAs solar cells with a range of architectures is studied. Solar cells with shallow and deep junction design processed on the native wafer as well as into a thin-film were irradiated by 1-MeV electrons with fluence up to 1x1015 e-/cm2 and by 1-MeV protons with fluence up to 1x1013 H+/cm2. The degradation of the cell performance due to irradiation was studied both experimentally and theoretically, with good agreement between modeled and measured data. We identify a degradation of the hetero-interfaces quality due to irradiation exposure, characterized by an increase of the interface recombination velocity. The solar cell performance degradation greatly depends on the junction depth and the thickness of the active layers, and therefore, a shallow junction solar cell processed into a thin-film geometry is found to be the most radiation resilient structure for space applications. The presence of a rear reflector allows the design of thinner devices that show potential for increased beginning-of-life performance and improved radiation hardness.

The paper presents a discussion on the thermal design of integrated power GaN devices. After a short out line of some critical thermal modelling issues, design guidelines are proposed on the basis of thermal simulations; the results presented suggest that for room temperature applications SiC substrate thinning (thus implying a microstrip process)is not mandatory from a thermal standpoint. This would open the possibility for coplanar GaN MMICs, already exploited for low-noise amplifiers, also in power circuits.

The paper presents a measurement-based largesignal distributed model for high-speed electroabsorption modulators, integrated within an RF circuit CAD environment. The model is implemented through a cascaded-cell approach; the identification of the nonlinear lumped equivalent circuit parameters of each cell through measurements is discussed and an example is provided of circuit extraction. An example of integrated driver-EAM simulation is finally discussed.

We present an efficient simulation technique to account for the thermal spreading effects of surface metallizations in the self-consistent dynamic electro-thermal analysis of power microwave devices. Electro-thermal self-consistency is achieved by solving the coupled nonlinear system made of a temperature dependent device electrical model, and of an approximate description of the device thermal behavior through a thermal impedance matrix. The numerical solution is pursued in the frequency domain by the Harmonic Balance technique. The approach is applied to the thermal stability analysis of power AlGaAs/GaAs HBTs and the results show that metallizations have a significant impact on the occurrence of the device thermal collapse.

We present a novel self-consistent time-domain model for the analysis and design of traveling-waveelectroabsorption modulators (TW-EAMs). The model fully accounts for the nonlinear interaction betweenthe microwave and optical traveling fields. The effects on the bandwidth and modulation efficiency of the nonuniform optical field distribution along the device are discussed. A few examples of application are presented, showing the model to be an efficient tool for the analysis, design and optimization of TW-EAMs for analog and digital applications.

A new self-consistent dynamic electro-thermal model for power HBTs is presented coupling a circuit-oriented electricalmodel, fitted on experimental data, with a full frequency domain thermal model. The thermal model provides the exact frequency behaviour of the device thermal impedance through a quasi-3D approach. The electro-thermal self-consistent solution is achieved, in large-signal periodic operation, through Harmonic Balance analysis. The model has been applied to the simulation of some HBT layouts from Alenia Marconi Systems.

The paper presents a new device for analog optical links, the balanced electroabsorption modulator, to allow the simultaneous cancellation of laser relative intensity noise, all even-order distortions, and third order intermodulation. The RF photonic link employing the new balanced modulator shows great improvement in the overall link performance with respect to conventional links using a single electroabsorption modulator. Moreover, it favorably compares with the to date highest performance links employing lithium niobate cross-coupled Mach-Zehnder modulators, proving itself an enabling technology for placement of all-semiconductor radio-frequency lightwave transmitters in high performance analog fiber optic links.