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Reflectometer Diagnostic Tool

Photo of a metal-framed desk-like unit, where the lower section contains electronic components and the upper section looks like two side-by-side cabinets, each of which contains light sources and sample stages. The reflectometer is a large optical sphere in the upper left.  A computer monitor and tower are on the right side.

Reflectometer that is one of the Stand-alone Measurements and Characterization tools in the Process Development and Integration Laboratory.

This page provides details on the reflectometer in the Stand-Alone Measurements and Characterization bays of the Process Development and Integration Laboratory. This capability should be operational within 2009.

The reflectometer allows fast measurements of the reflectance spectrum by spectrometry measurements and acquiring filtered images of the entire cell in camera mode. From this, we can gather many material-related parameters while fabricating solar cells.


  • Monitoring of wafer sawing, texture etching, antireflective coating, front-metal patterning, and back metallization
  • Directly measuring reflectance vs. average wavelength in spectrometer mode, and wavelength as a function of position with camera mode
  • Indirectly measuring antireflective coating thickness, surface roughness, wafer thickness, metallization area, and metallization height.

Special features:

  • Manufactured by GT Solar, but developed by NREL
  • Manual sample handling
  • Wavelength range in spectrometer mode is 0.4 to 1.5 μm
  • Automatic switching between camera and spectrometer modes
  • Atmosphere is air
  • Measurements typically take <100 ms
  • Uses multiple, wide-angle light sources for large-area samples
  • Reproducibility within ±1%

Contact Bhushan Sopori for more details on these capabilities.