Spectral quantum efficiency

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.