1,721,010 research outputs found
Computational Efficient Solution of Maxwell's Equations for Lamellar Gratings
No full textIn this work, a new implementation of the analytic modal method (AMM) based
on an improved and computationally e±cient approach to calculate the eigenvalues and corre-
sponding eigenfunctions of the Helmholtz equation is presented. In case of TE polarization the
computational time is remarkably reduced by adopting the perturbation approach. The portion
of the computation time required to calculate eigenfunctions in case of TE polarization become
almost negligible when a large number of eigenfunctions in the expansion is used. In case of TM
polarization we use the pseudospectral method to calculate an initial guess solution for eigenval-
ues which are subsequently re ̄ned by Newton's method. The proposed improved AMM allows
to calculate the electromagnetic ̄eld in arbitrary stack of lamellar gratings
Understanding the Influence of Busbars in Large-Area IBC Solar Cells by Distributed SPICE Simulations
Full text linkIn this paper, we model a large-area high-efficiency interdigitated back-contact (IBC) solar cell by means of a distributed electrical network. The simulation tool allows accounting for the distributed resistive effects in diffusions and metallization. The model also considers the electrical shading effect and resistive losses due to both back-surface field (BSF) and emitter busbars. A calibrated model is used to investigate the case of a large-area (15.6 × 15.6 cm2) IBC cell, in which we investigate the influence of key busbar parameters: number of busbars, busbar width, soldering pitch (for module connection), and metal sheet resistance. The predictive simulations allow finding out the optimum number of busbars, arising from a tradeoff between the electrical shading effect due to the BSF busbars and resistive losses due to the emitter busbars and the fingers. Moreover, we show how the distance between soldering points on the metal busbars influences the choice of the busbar width. We found out that if an adequate number (>7) of soldering points is adopted, the busbar width should be kept lower than 0.5 mm. On the other hand, the adoption of a thick Cu-plating (15 μm) leads to an increase of efficiency of 0.2%abs with respect to the case of sputtered Al metal (3 μm thick)
A Distributed Electrical Model for Interdigitated back Contact Silicon Solar Cells
No full textIn this paper we introduce a quasi 3-D electrical model for a high efficiency interdigitated back contact (IBC) solar cell. This distributed electrical network is based on two-diodes circuit elementary units. It allows accounting for the resistive losses due to the transport through the emitter, the back surface field (BSF) and the fingers and busbars metallization. Moreover, it can model the electrical shading losses attributed to the BSF busbar. We calibrated the electrical components of the model according to experimental measurements on real devices. The validity of the model is demonstrated by the good agreement between simulation and experimental results for dark and illuminated IV measurements with and without masked busbars. The model can now easily be applied to simulate and optimize different metal grid layouts
Particle-based simulation of charge transport in discrete-charge nano-scale systems: the electrostatic problem
Full text linkThe fast and accurate computation of the electric forces that drive the motion of charged particles at the nanometer scale represents a computational challenge. For this kind of system, where the discrete nature of the charges cannot be neglected, boundary element methods (BEM) represent a better approach than finite differences/finite elements methods. In this article, we compare two different BEM approaches to a canonical electrostatic problem in a three-dimensional space with inhomogeneous dielectrics, emphasizing their suitability for particle-based simulations: the iterative method proposed by Hoyles et al. and the Induced Charge Computation introduced by Boda et al
Analysis of Silicon Solar Cells With Poly-Si/SiOx Carrier-Selective Base and Emitter Contacts
Full text linkPassivating contacts are a promising technology to enhance silicon solar cells conversion efficiency. In this paper, we present a simulation study carried out by using physical models calibrated on the basis of experimental data, aimed at understanding the electrical properties of front emitter silicon solar cells featuring top/rear poly-Si/SiO x selective contacts. Furthermore, we propose a rear junction (RJ) design that desensitizes the fill factor to top electrode resistivity. According to our simulations, the RJ scheme addresses the possibility to omit the transparent conductive oxide allowing promising conversion efficiency of silicon solar cells with carrier-selective contacts. In addition, the influence of the surface recombination velocity at the c-Si/SiO x interfaces and of the effective tunneling masses is investigated
Modeling self-heating effects in AlGaN/GaN electronic devices during static and dynamic operation mode
Full text linkIn this paper, we present a study of the self-heating effects in GaN-based power devices during static and dynamic operation mode by means of Sentaurus TCAD. A physical model interface (PMI), accounting for the temperature dependence of the thermal boundary resistance (TBR), has been implemented in the simulator in order to realistically model self-heating effects. In particular, we take into account for the TBR associated to the nucleation layer between GaN and SiC substrate. Moreover, the thermal contribution of the mutual heating among adjacent devices has been considered. Finally, we have investigated the influence of the temperature on the surface charges trapping and de-trapping phenomena showing two different traps occupancy transients. While one of the two occurs also in the isothermal condition, the second one is temperature activated
Analysis of the impact of geometrical and technological parameters on recombination losses in interdigitated back-contact solar cells
No full textThis paper presents a detailed analysis of the recombination losses in an interdigitated back-contact (IBC) solar cell by means of three-dimensional numerical simulation. In particular, we discuss about the influence of geometrical and technological parameters such as the bulk thickness, the emitter contact fraction and the passivation effectiveness of the gap region on the saturation current density and on the carrier collection efficiency at region and mechanism-wise level. Moreover, the simulation results in terms of main figures of merit of the solar cell are reported and discussed. The paper shows that, except for the parasitic resistive losses, the optimum contact fraction at the emitter and base strongly depends on the presence of physical competing mechanisms, such as the internal optical bottom reflectivity and the recombination losses at the passivated emitter and base. In addition, the study underlines the critical role played by the passivation properties of the gap region, which may potentially be detrimental in terms of Fill-Factor and conversion efficiency
NBTI in p-channel power U-MOSFETs: Understanding the degradation and the recovery mechanisms
No full textIn this paper, we present an analysis of the degradation mechanisms in p-channel power U-MOSFETs due to Negative Bias Temperature Instability (NBTI). In particular, we study the influence of NBTI on threshold voltage and trans-conductance, which are the main figures of merit affected by charges trapping in the bulk oxide and by an interface defects generation. At the end of the stress, a recovery phase is implemented in order to monitor permanent and recoverable degradation. Moreover, we investigate the influence of the overall channel area on the threshold voltage degradation and on device lifetime
Influence of bias and temperature conditions on NBTI physical mechanisms in p-channel power U-MOSFETs
No full textIn this paper, we present an analysis of the degradation and recovery mechanisms in p-channel power U-MOSFETs due to Negative Bias Temperature Instability (NBTI). In particular, we study the influence of NBTI on threshold voltage and sub-threshold slope, which are the main figures of merit affected by charge trapping in the oxide and by interface state generation. The temperature and bias dependence of NBTI phenomena have been investigated. As a result, we report a higher degradation with the temperature and gate bias increase. On the other hand, by monitoring the recovery phase in different conditions, we found out similar behaviors heavily reported in CMOS technology, which are: (i) recovery mechanism is mainly due to oxide detrapping charge; (ii) higher temperatures allow a faster and larger recovery, hence it is an accelerator factor also for this mechanism; (iii) the oxide defects, involved in the detrapping phase, have an energy position confined in the band-gap of the silicon
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