The Experts below are selected from a list of 324 Experts worldwide ranked by ideXlab platform

Karin Hinzer - One of the best experts on this subject based on the ideXlab platform.

  • Representative Atmospheric Parameters in Multijunction Solar Cell Design
    IEEE Journal of Photovoltaics, 2018
    Co-Authors: Mark D. Yandt, Karin Hinzer, Henry Schriemer
    Abstract:

    The representative spectrum selection approach is applied systematically to determine efficiency-maximizing Multijunction Solar Cell (MJSC) bandgap combinations that also maximize energy yield (EY). The technique is performed using a complete, validated dataset of annual spectral irradiance measurements collected in Ottawa, Canada, and compared to the same calculation using simulated spectra with fixed representative atmospheric parameters. We confirm that representative atmospheric parameters exist, are identified with their median direct normal irradiance values, and show that they accurately predict maximized EYs at the MJSC design points. Representative spectra, for MJSCs of 2-8 junctions, are determined as a function of aerosol optical depth (AOD) and precipitable water (PW). Coefficients that describe the change in the EY and representative spectrum as a function of changing representative AOD and PW from one location to another are presented.

  • Efficient Multijunction Solar Cell Design for Maximum Annual Energy Yield by Representative Spectrum Selection
    IEEE Journal of Photovoltaics, 2017
    Co-Authors: Mark D. Yandt, Karin Hinzer, Henry Schriemer
    Abstract:

    We describe a systematic approach to Multijunction Solar Cell (MJSC) design that unambiguously identifies the spectrum to be used in Cell optimization such that local annual energy yield is maximized. A set of candidate spectra is generated from air mass (AM) values ranging from AM1d to AM5d. Each candidate spectrum is used to find the bandgap combination that maximizes Cell efficiency and its energy yield is then calculated using an efficient data reduction approach. The bandgap combination that maximizes annual energy yield identifies the representative spectrum. We do this for Cells with up to eight junctions across all clear-sky latitudes and compare our results to other Cell optimization approaches. Our representative spectrum selection (RSS) approach is robust and highly tolerant of variations in latitude, particularly when compared to the standard AM1.5d approach which, at midlatitudes, cannot be used without suffering an increasingly severe yield penalty. Comparison against the 50% cumulative energy AM (50% AM) design approach is enabled by using the same design conditions (sea level and ASTM standard atmosphere) in order to unambiguously associate each 50% AM value with a Cell design spectrum. We find that our RSS approach always produces Cells with slightly higher annual energy yields than are achieved by the corresponding 50% AM designs. While both approaches show similar yields for devices with few junctions, we find yield enhancements approaching 1% for Cell designs with many junctions, emphasizing the need to consider the spectral variability of the local Solar resource. This consideration is systematically enabled by our RSS approach, addressing a deficiency in the previous design approaches.

  • Tunnel-Junction-Limited Multijunction Solar Cell Performance Over Concentration
    IEEE Journal of Selected Topics in Quantum Electronics, 2013
    Co-Authors: Alex W. Walker, Olivier Thériault, Matthew M. Wilkins, Jeffrey F. Wheeldon, Karin Hinzer
    Abstract:

    The simulation of tunnel junctions is performed by using nonlocal band-to-band and trap assisted tunneling models that are capable of reproducing the experimental current-voltage characteristics of p++AlGaAs/ n++AlGaAs and p++AlGaAs/ n++GaAs based devices. These simulated characteristics are then implemented within a lattice matched InGaP/(In)GaAs/Ge Multijunction Solar Cell (MJSC) to assess the performance as a function of tunnel junction layer doping in the regime where the TJ limits the performance of the MJSC. At 500 suns, a 4.6% absolute drop in simulated efficiency is observed for an AlGaAs/GaAs bottom TJ corresponding to a degenerately p-doped layer of 2.5 × 1019 cm-3 compared to a TJ with a doping of 4×1020 cm-3. A minimum p++ doping level of 3.3 × 10 19 cm-3 is required in order to avoid bottom TJ limitation up to 1000 suns concentration for an n++ doping of 2 × 1019 cm-3 based on the calibrated models. Furthermore, the effects of the peak and valley current densities are shown to have a strong influence on the efficiency over concentration within the TJ limiting regime.

  • Multijunction Solar Cell Designs Using Silicon Bottom SubCell and Porous Silicon Compliant Membrane
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Matthew M. Wilkins, Jeffrey F. Wheeldon, Abderraouf Boucherif, Richard Beal, Joan E. Haysom, Vincent Aimez, Richard Arès, Trevor J. Hall, Karin Hinzer
    Abstract:

    A novel approach to the design of Multijunction Solar Cells on silicon substrates for 1-sun applications is described. Models for device simulation, including porous silicon layers, are presented. A silicon bottom subCell is formed by diffusion of dopants into a silicon wafer. The top of the wafer is porosified to create a compliant layer, and a III-V buffer layer is then grown epitaxially, followed by middle and top subCells. Because of the resistivity of the porous material, these designs are best suited to high-efficiency 1-sun applications. Numerical simulations of a Multijunction Solar Cell that incorporates a porous silicon-compliant membrane indicate an efficiency of 30.7% under AM1.5G, 1-sun for low-threading dislocation density, decreasing to 23.7% for a TDD of 107 cm-2.

  • The Effects of Absorption and Recombination on Quantum Dot Multijunction Solar Cell Efficiency
    IEEE Journal of Photovoltaics, 2013
    Co-Authors: Alex W. Walker, Olivier Thériault, Jeffrey F. Wheeldon, Karin Hinzer
    Abstract:

    The key characteristics of quantum dot (QD)-enhanced Multijunction Solar Cells (MJSC) are explored theoretically by focusing on the generation and recombination rates throughout the QD layers in the middle subCell. The quantum dots are modeled using an effective medium to describe light absorption, confinement, and recombination properties. We report an 8% increase in the short-circuit current density accompanied by a 3% drop in an open-circuit voltage for a QD- enhanced MJSC at 1 sun illumination (1 kW/m2) compared with a control MJSC without QD. The drop in an open-circuit voltage is due in part to the increased recombination rates in the depletion region, decreased carrier lifetimes in the QDs, and the increased recombination rates resulting from carrier escape and capture. Overall, these contribute to an absolute increase in efficiency of over 1% for the studied QD-enhanced MJSC design for a QD density of 125 QD/μm2.

Chihhung Wu - One of the best experts on this subject based on the ideXlab platform.

  • performance improvement of nh4 2s x treated iii v compounds Multijunction Solar Cell using surface treatment
    Journal of The Electrochemical Society, 2008
    Co-Authors: Jiunting Chen, Chihhung Wu
    Abstract:

    To improve the conversion efficiency of tandem-type III-V Multijunction Solar Cells, the (NH 4 ) 2 S x -treatment method was used to passivate the surface of the window layer (AlInP) of the Cell. The conversion efficiency of the (NH 4 ) 2 S x -treated Multijunction Solar Cell was increased more than 4%. Using X-ray photoelectron spectroscopy and current-voltage measurements, the mechanism of the conversion efficiency improvement is attributed to the reduction of the surface states by sulfidation passivation. It is indicated that the (NH 4 ) 2 S x treatment is an effective method for improving the performance of III-V compound Multijunction Solar Cells.

  • Performance Improvement of ( NH4 ) 2S x -Treated III–V Compounds Multijunction Solar Cell Using Surface Treatment
    Journal of The Electrochemical Society, 2008
    Co-Authors: Jiunting Chen, Chihhung Wu
    Abstract:

    To improve the conversion efficiency of tandem-type III-V Multijunction Solar Cells, the (NH 4 ) 2 S x -treatment method was used to passivate the surface of the window layer (AlInP) of the Cell. The conversion efficiency of the (NH 4 ) 2 S x -treated Multijunction Solar Cell was increased more than 4%. Using X-ray photoelectron spectroscopy and current-voltage measurements, the mechanism of the conversion efficiency improvement is attributed to the reduction of the surface states by sulfidation passivation. It is indicated that the (NH 4 ) 2 S x treatment is an effective method for improving the performance of III-V compound Multijunction Solar Cells.

Iván Garcia - One of the best experts on this subject based on the ideXlab platform.

  • and Multijunction Solar Cell Design
    2020
    Co-Authors: Iván Garcia, Aron Habte, Myles A. Steiner, William E Mcmahon, John F. Geisz, Manajit Sengupta
    Abstract:

    Annual spectra sets be used for accurate energy production prediction and Multijunction Solar Cell design for maximum energy production at a specific site. These spectra sets contain a large quantity of data that is cumbersome to manage during Solar Cell design calculations and impractical to reproduce in Solar simulators for indoor energy production measurements. However, it should be possible to bin together spectra with similar spectral contents, and then use this reduced set with little loss of accuracy. We present two binning algorithms which judiciously bin together similar spectra to create a much smaller "proxy" set, for which the total measurement time, energy production calculation and Solar Cell optimization decreases to a matter of seconds. These algorithms are assessed against their accuracy in representing the whole spectra sets for Solar Cell design and energy production prediction. We find that a set of just five spectra fulfills this requirement. In addition, the sets of proxy spectra act as "fingerprints" of specific sites, and provide an efficient and effective way to understand how Cell design and performance vary from site to site. Furthermore, the process of reducing a full data set to a few proxy spectra can help assess the quality of the dataset for Multijunction applications, and contribute to improvements to the datasets and data collection methods.

  • Evidence of enhanced Zn-diffusion observed during the growth of Inverted Metamorphic Solar Cells
    2019 IEEE 46th Photovoltaic Specialists Conference (PVSC), 2019
    Co-Authors: Manuel Hinojosa, Iván Garcia, Ignacio Rey-stolle, Carlos Algora
    Abstract:

    Zinc-diffusion can induce multiple failures in the electrical performance of a Multijunction Solar Cell. In this work, we show an important Zn-diffusion from the AlGaInP back-surface-field layer to the emitter of the GaInP top Cell of an inverted Multijunction Solar Cell. Through the analysis of different doping profiles, we provide strong evidence that the diffusion mechanism is (1) triggered by the growth of the tunnel junction cathode and (2) involves point defects. We analyze the implications of Zn-diffusion on the bandgap, the rear-passivation and the minority carrier quality of the GaInP Solar subCell by relating the electrical performance of different samples to its corresponding doping profile.

  • spectral binning for energy production calculations and Multijunction Solar Cell design
    Progress in Photovoltaics, 2018
    Co-Authors: Iván Garcia, Aron Habte, Myles A. Steiner, Manajit Sengupta, William E Mcmahon, John F. Geisz, Daniel J. Friedman
    Abstract:

    Currently, most Solar Cells are designed for and evaluated under standard spectra intended to represent typical spectral conditions. However, no single spectrum can capture the spectral variability needed for annual energy production (AEP) calculations, and this shortcoming becomes more significant for series-connected Multijunction Cells as the number of junctions increases. For this reason, AEP calculations are often performed on very detailed yearlong sets of data, but these pose 2 inherent challenges: (1) These data sets comprise thousands of data points, which appear as a scattered cloud of data when plotted against typical parameters and are hence cumbersome to classify and compare, and (2) large sets of spectra bring with them a corresponding increase in computation or measurement time. Here, we show how a large spectral set can be reduced to just a few “proxy” spectra, which still retain the spectral variability information needed for AEP design and evaluation. The basic “spectral binning” methods should be extensible to a variety of Multijunction device architectures. In this study, as a demonstration, the AEP of a 4-junction device is computed for both a full set of spectra and a reduced proxy set, and the results show exCellent agreement for as few as 3 proxy spectra. This enables much faster (and thereby more detailed) calculations and indoor measurements and provides a manageable way to parameterize a spectral set, essentially creating a “spectral fingerprint,” which should facilitate the understanding and comparison of different sites.

  • Degradation of Ge subCells by thermal load during the growth of Multijunction Solar Cells
    Progress in Photovoltaics, 2017
    Co-Authors: Enrique Barrigon, Iván Garcia, Carlos Algora, M. Ochoa, Laura Barrutia, Ignacio Rey-stolle
    Abstract:

    Germanium Solar Cells are used as bottom subCells in many Multijunction Solar Cell designs. The question remains whether the thermal load originated by the growth of the upper layers of the Multijunction Solar Cell structure affects the Ge subCell performance. Here, we report and analyze the performance degradation of the Ge subCell due to such thermal load in lattice-matched GaInP/Ga(In)As/Ge triple-junction Solar Cells. Specifically, we have detected a quantum efficiency loss in the wavelength region corresponding to the emitter layer (which accounts for up to 20% loss in equivalent JSC) and up to 55 mV loss in VOC of the Ge subCell as compared with analogous devices grown as single-junction Ge Solar Cells on the same type of substrates. We prove experimentally that there is no direct correlation between the loss in VOC and the doping level of the base. Our simulations show that both the JSC and VOC losses are consistent with a degradation of the minority carrier properties at the emitter, in particular at the initial nanometers of the emitter next to the emitter/window heterointerface. In addition, we also rule out the gradual emitter profile shape as the origin of the degradation observed. Our findings underscore the potential to obtain higher efficiencies in Ge-based Multijunction Solar Cells if strategies to mitigate the impact of the thermal load are taken into consideration. (Less)

  • Field spectra binning for energy production calculations and Multijunction Solar Cell design
    2015 IEEE 42nd Photovoltaic Specialist Conference (PVSC), 2015
    Co-Authors: Iván Garcia, Aron Habte, Myles A. Steiner, Manajit Sengupta, William E Mcmahon, John F. Geisz, Daniel J. Friedman
    Abstract:

    Annual spectra sets must be used for accurate energy production prediction and Multijunction Solar Cell design for maximum energy production at a specific site. These spectra sets contain a large quantity of data that is cumbersome to manage during Solar Cell design calculations and impractical to reproduce in Solar simulators for indoor energy production measurements. However, it should be possible to bin together spectra with similar spectral contents, and then use this reduced set with little loss of accuracy. We present two binning algorithms which judiciously bin together similar spectra to create a much smaller “proxy” set, for which the total measurement time, energy production calculation and Solar Cell optimization decreases to a matter of seconds. These algorithms are assessed against their accuracy in representing the whole spectra sets for Solar Cell design and energy production prediction. We find that a set of just five spectra fulfills this requirement. In addition, the sets of proxy spectra act as “fingerprints” of specific sites, and provide an efficient and effective way to understand how Cell design and performance vary from site to site. Furthermore, the process of reducing a full data set to a few proxy spectra can help assess the quality of the dataset for Multijunction applications, and contribute to improvements to the datasets and data collection methods.

ALLEN M BARNETT - One of the best experts on this subject based on the ideXlab platform.

  • wide band gap gallium phosphide Solar Cells
    IEEE Journal of Photovoltaics, 2012
    Co-Authors: Xuesong Lu, Susan R Huang, Martin Diaz, Nicole A Kotulak, Ruiying Hao, R L Opila, ALLEN M BARNETT
    Abstract:

    Gallium phosphide (GaP), with its wide band gap of 2.26 eV, is a good candidate for the top junction Solar Cell in a Multijunction Solar Cell system. Here, we design, fabricate, characterize, and analyze GaP Solar Cells. Liquid phase epitaxy is used to grow the semiconductor layers. Four generations of GaP Solar Cells are developed and fabricated with each Solar Cell structure being designed and improved based on the first principles analyses of the predecessor Solar Cells. Quantum efficiency and current-voltage measurements are used to analyze the Solar Cell performance and to develop predictive models. We create a GaP Solar Cell with an efficiency of 2.42% under AM 1.5G one sun illumination.

Jiunting Chen - One of the best experts on this subject based on the ideXlab platform.

  • performance improvement of nh4 2s x treated iii v compounds Multijunction Solar Cell using surface treatment
    Journal of The Electrochemical Society, 2008
    Co-Authors: Jiunting Chen, Chihhung Wu
    Abstract:

    To improve the conversion efficiency of tandem-type III-V Multijunction Solar Cells, the (NH 4 ) 2 S x -treatment method was used to passivate the surface of the window layer (AlInP) of the Cell. The conversion efficiency of the (NH 4 ) 2 S x -treated Multijunction Solar Cell was increased more than 4%. Using X-ray photoelectron spectroscopy and current-voltage measurements, the mechanism of the conversion efficiency improvement is attributed to the reduction of the surface states by sulfidation passivation. It is indicated that the (NH 4 ) 2 S x treatment is an effective method for improving the performance of III-V compound Multijunction Solar Cells.

  • Performance Improvement of ( NH4 ) 2S x -Treated III–V Compounds Multijunction Solar Cell Using Surface Treatment
    Journal of The Electrochemical Society, 2008
    Co-Authors: Jiunting Chen, Chihhung Wu
    Abstract:

    To improve the conversion efficiency of tandem-type III-V Multijunction Solar Cells, the (NH 4 ) 2 S x -treatment method was used to passivate the surface of the window layer (AlInP) of the Cell. The conversion efficiency of the (NH 4 ) 2 S x -treated Multijunction Solar Cell was increased more than 4%. Using X-ray photoelectron spectroscopy and current-voltage measurements, the mechanism of the conversion efficiency improvement is attributed to the reduction of the surface states by sulfidation passivation. It is indicated that the (NH 4 ) 2 S x treatment is an effective method for improving the performance of III-V compound Multijunction Solar Cells.