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Mark A. Ratner - One of the best experts on this subject based on the ideXlab platform.

  • Universality of non-ohmic shunt leakage in thin-film Solar Cells
    Journal of Applied Physics, 2010
    Co-Authors: Sourabh Dongaonkar, Jonathan D. Servaites, Grayson M. Ford, Stephen Loser, James E. Moore, Ryan M. Gelfand, Hooman Mohseni, Hugh W. Hillhouse, Rakesh Agrawal, Mark A. Ratner
    Abstract:

    We compare the dark current-voltage (IV) characteristics of three different thin-film Solar Cell Types: hydrogenated amorphous silicon (a-Si:H) p-i-n Cells, organic bulk heterojunction (BHJ) Cells, and Cu(In,Ga)Se2 (CIGS) Cells. All three device Types exhibit a significant shunt leakage current at low forward bias (V

Otwin Breitenstein - One of the best experts on this subject based on the ideXlab platform.

  • Short-Circuit Current Density Imaging Via PL Image Evaluation Based on Implied Voltage Distribution
    IEEE Journal of Photovoltaics, 2015
    Co-Authors: Hannes Höffler, Otwin Breitenstein, Jonas Haunschild
    Abstract:

    Luminescence imaging has found wide application for the characterization of silicon Solar Cells and wafers over the past decade. One special application is based on a combination of electroluminescence and photoluminescence imaging. Images of a single Solar Cell at different operating conditions are taken. With suitable methods, it is possible to evaluate the image series and extract spatially resolved Solar Cell parameters. In the past, methods have been introduced focusing on the extraction of local dark saturation current density and local series resistance. Past methods usually assumed a laterally homogeneous short-circuit current density corresponding to laterally homogeneous external quantum efficiency. In this study, we give a step-by-step description of a newly developed method, which does not rely on the assumption of homogeneous short-circuit current density. The evaluation method instead additionally yields an image of the local short-circuit current density or of the external quantum efficiency. We apply the method to different Solar Cell Types, and we give a detailed comparison to its predecessor the “coupled determination of dark saturation current density and series resistance” method. We compare the short-circuit current density images with images obtained from the “light beam-induced current” technique.

  • CLASSIFICATION OF SHUNTING MECHANISMS IN CRYSTALLINE SILICON Solar CellS
    Solar Energy Materials and Solar Cells, 2001
    Co-Authors: Martin Langenkamp, Otwin Breitenstein
    Abstract:

    Abstract The efficiency of a Solar Cell is given by its average electrical parameters. On inhomogeneous materials and especially on large-area Solar Cells the inhomogeneity of the short circuit current, the open circuit voltage and the fill factor are important factors to reach high and stable efficiencies and may limit the overall performance of the device. A locally increased dark forward current (shunt) reduces the fill factor and the open circuit voltage of the whole Cell. The inhomogeneity of the forward current in a Solar Cell can be measured using lock-in thermography. The quantitative and voltage-dependent evaluation of these thermographic investigations of various Solar Cell Types on mono- or multi-crystalline silicon enables the classification of the different shunting mechanisms found. By further microscopic investigations the physical reasons for the increased dark forward currents can be determined. It turns out that a high density of crystallographic defects like dislocation tangles or microdefects can be responsible for an increased dark forward current. Unexpectedly, grain boundaries in Solar Cells on multicrystalline silicon do not show any measurable influence on the local dark forward current. In most cases shunts caused by process-induced defects are dominating the current–voltage characteristic at the maximum power point of the Solar Cell. In commercial Solar Cells shunts at the edges are most important, followed by shunts beyond the grid lines.

Thorsten Trupke - One of the best experts on this subject based on the ideXlab platform.

  • Low temperature sensitivity of implied voltages from luminescence measured on crystalline silicon Solar Cells
    Solar Energy Materials and Solar Cells, 2019
    Co-Authors: Iskra Zafirovska, Mattias K. Juhl, Alison Ciesla, Rhett Evans, Thorsten Trupke
    Abstract:

    Abstract Performance monitoring of crystalline silicon Solar Cells often requires terminal voltage measurements, which are strongly influenced by the sample temperature via the large temperature dependence of the intrinsic carrier density. The impact of sample temperature variations can be corrected for by using the temperature coefficient of the terminal voltage, however this relies on having both accurate values for the temperature coefficient and accurate measurements of the sample temperature. This paper demonstrates that in situations where the sample temperature cannot be accurately measured, for example in some high volume production facilities or during module degradation experiments, implied voltages determined from either electroluminescence or photoluminescence provide a more accurate measure of sample performance than the terminal voltage. The results presented here show that implied voltages exhibit a temperature sensitivity that is one order of magnitude lower than that of the terminal voltage. This is largely due to the fact that luminescence intensity is not strongly temperature dependent around room temperature. This is confirmed by experimental temperature dependent measurements on four different crystalline silicon Solar Cell Types. The benefit of using implied voltage measurements over temperature corrected terminal voltage measurements for the monitoring of light and elevated temperature induced degradation in silicon Solar modules is demonstrated.

  • On the use of voltage measurements for determining carrier lifetime at high illumination intensity
    2017 IEEE 44th Photovoltaic Specialist Conference (PVSC), 2017
    Co-Authors: Robert Dumbrell, Mattias K. Juhl, Thorsten Trupke, Ziv Hameiri
    Abstract:

    Illumination intensity dependent open circuit voltage measurements (commonly known as Suns- $\boldsymbol{V_{oc}}$ ) are often used to measure the current-voltage characteristic of a Solar Cell without the impact of series resistance. Deviations have previously been reported between Suns- $\boldsymbol{V_{oc}}$ measurements and contactless measurements, such as injection-dependent photoluminescence (Suns-PL) at high illumination levels. These deviations are analyzed in detail in this paper and shown to cause significant errors when converting Suns- $\boldsymbol{V_{oc}}$ data to injection-dependent minority carrier lifetimes. Experimental data are used to demonstrate the magnitude of this effect for a range of different Solar Cell Types.

Sourabh Dongaonkar - One of the best experts on this subject based on the ideXlab platform.

  • Universality of non-ohmic shunt leakage in thin-film Solar Cells
    Journal of Applied Physics, 2010
    Co-Authors: Sourabh Dongaonkar, Jonathan D. Servaites, Grayson M. Ford, Stephen Loser, James E. Moore, Ryan M. Gelfand, Hooman Mohseni, Hugh W. Hillhouse, Rakesh Agrawal, Mark A. Ratner
    Abstract:

    We compare the dark current-voltage (IV) characteristics of three different thin-film Solar Cell Types: hydrogenated amorphous silicon (a-Si:H) p-i-n Cells, organic bulk heterojunction (BHJ) Cells, and Cu(In,Ga)Se2 (CIGS) Cells. All three device Types exhibit a significant shunt leakage current at low forward bias (V

Geoffrey A. Landis - One of the best experts on this subject based on the ideXlab platform.

  • The Solar Spectrum on the Martian Surface and its Effect on Photovoltaic Performance
    2006 IEEE 4th World Conference on Photovoltaic Energy Conference, 2006
    Co-Authors: Geoffrey A. Landis, Dan Hyatt
    Abstract:

    Solar Cells operating on the surface of Mars receive a spectrum of illumination different from the AM0 spectrum, since the sunlight is filtered by dust suspended in the atmosphere. This spectrum changes with the amount of dust in the atmosphere, as well as with air mass change due to time of day and season. This spectral variation affects the performance of Solar Cells. We used data from Mars Exploration Rovers to measure this spectrum. By comparing the measured intensity with the known reflectance of the pancam calibration target on the rovers Spirit and Opportunity, we measure the Solar spectrum reaching the surface. The effect of this spectrum on the performance of Solar Cells is then calculated based on the spectral response of several different Solar Cell Types

  • Mars Array Technology Experiment Developed to Test Solar Arrays on Mars
    2001
    Co-Authors: Geoffrey A. Landis
    Abstract:

    Solar arrays will be the power supply for future missions to the planet Mars, including landers, rovers, and eventually human missions to explore the Martian surface. Until Mars Pathfinder landed in July 1997, no Solar array had been used on the surface. The MATE package is intended to measure the Solar energy reaching the surface, characterize the Martian environment to gather the baseline information required for designing power systems for long-duration missions, and to quantify the performance and degradation of advanced Solar Cells on the Martian surface. To measure the properties of sunlight reaching the Martian surface, MATE incorporates two radiometers and a visible/NIR spectrometer. The radiometers consist of multiple thermocouple junctions using thin-film technology. These devices generate a voltage proportional to the Solar intensity. One radiometer measures the global broadband Solar intensity, including both the direct and scattered sunlight, with a field of view of approximately 130. The second radiometer incorporates a slit to measure the direct (unscattered) intensity radiation. The direct radiometer can only be read once per day, with the Sun passing over the slit. The spectrometer measures the global Solar spectrum with two 256-element photodiode arrays, one Si sensitive in the visible range (300 to 1100 nm), and a second InGaAs sensitive to the near infrared (900 to 1700 nm). This range covers 86 percent of the total energy from the Sun, with approximately 5-nm resolution. Each photodiode array has its own fiber-optic feed and grating. Although the purpose of the MATE is to gather data useful in designing Solar arrays for Mars surface power systems, the radiometer and spectrometer measurements are expected to also provide important scientific data for characterizing the properties of suspended atmospheric dust. In addition to measuring the Solar environment of Mars, MATE will measure the performance of five different individual Solar Cell Types and two different Solar Cell strings, to qualify advanced Solar Cell Types for future Mars missions. The MATE instrument, designed for the Mars-2001 Surveyor Lander mission, contains a capable suite of sensors that will provide both scientific information as well as important engineering data on the operation of Solar power systems on Mars. MATE will characterize the intensity and spectrum of the Solar radiation on Mars and measure the performance of Solar arrays in the Mars environment. MATE flight hardware was built and tested at the NASA Glenn Research Center and is ready for flight.

  • The Photovoltaic Engineering Testbed: Design options and trade-offs
    AIP Conference Proceedings, 2000
    Co-Authors: Geoffrey A. Landis, Andrew Sexton, Richard Abramczyk, Joseph Francz, D. B. Johnson, Liu Yang, Daniel Minjares, James Myers
    Abstract:

    The Photovoltaic Engineering Testbed (PET) is a space-exposure test facility to fly on the International Space Station to calibrate, test, and qualify advanced Solar Cell Types in the space environment. The purpose is to reduce the cost of validating new technologies and bringing them to spaceflight readiness by measuring them in the in-space environment. This paper reviews engineering options considered for flying PET on the International Space Station, and presents the current status of development.

  • An engineering research testbed for photovoltaics
    AIP Conference Proceedings, 1999
    Co-Authors: Geoffrey A. Landis, Andrew Sexton
    Abstract:

    The Ohio Aerospace Institute and the NASA Lewis Research Center are designing and building a Solar-Cell calibration facility, the Photovoltaic Engineering Testbed (PET) to fly on the International Space Station to calibrate, measure, and qualify advanced Solar Cell Types in the space environment. PET will serve three primary functions: calibration, measurement, and qualification of Solar Cells, in order to bring new Solar Cell technologies to spaceflight readiness.

  • A Testbed for Testing Materials Properties in Space
    MRS Online Proceedings Library, 1998
    Co-Authors: Geoffrey A. Landis, Sheila G. Bailey, Andrew Sexton
    Abstract:

    The Photovoltaic Engineering Testbed (PET) is a facility to fly on the International Space Station to test advanced Solar Cell Types in the space environment. The purpose is to reduce the cost of validating new technologies and bringing them to spaceflight readiness by measuring them in the in-space environment. The facility is scheduled to be launched in 2002.