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Spectral quantum efficiency

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    Spectral quantum efficiency& reflectance

    This tool is designed for the automated IQE analysis of
    crystalline silicon solar cells. Some features are:

    • The solar cells are illuminated with variable light, either homogeneously over an area of 20 x 20 mm,
      or with a focussed spot of approx. 1 x 3 mm².
    • Full area EQE & reflectance measurements by moving the 4 cm² illuminated area continuously.
    • Monochromatic light between 280-1600 nm from monochromator (2 gratings, slit width and order filter changed automatically). Typically used bandwidth is 8 nm FWHM and the wavelength accuracy is 1 nm.
    • White bias light up to 1.2 suns is restricted to the area of monochromatic illumination.
    • Bias-ramp for automatic determination of the correct bias light intensity for quasi-absolute EQE measurements
      in only one wavelength scan. The procedure is also useful to check the linearity of the solar cell.
    • The reflectance is measured under an 8° tilted beam of 2 x 2 cm² area with a BaSO4-coated integrating sphere.
    • Batch mode for series of measurements under different conditions.
    • The solar cells are held on a temperature controlled vacuum chuck (25 °C) which can be moved by a motorized
      x-y-z stage. The temperature is measured directly at the back of the solar cell.
    • Transimpedance amplifier (max. 200 mA) holds solar cell at short circuit with remote sense
      and contact quality check.
    • Automatic calibration of EQE and reflectance
      • –  increases throughput and reduces the necessary time of operator interaction.
      • –  makes the operation safer against human errors (misalignment, bias light, etc).
      • –  avoids degradation of the reference solar cell by manual handling.
    • Motorized contact-setting and change-over between EQE and reflectance measurements.
    • Data analysis by comparison with analytical electrical and optical model.
    • Duration:
      • –  ca. 1 sec. per wavelength for spot measurement (2 x 2 cm²)
      • –  ca. 9 sec. per wavelength for 12.5 x 12.5 cm² solar cell
      • –  ca. 12 sec. per wavelength for 15.6 x 15.6 cm² solar cell
    • EQE and reflectance mapping with focussed light spot (QMAP)
      within 5 min for a 15.6 x 15.6 cm² cell per map and wavelength.