Optical mapping of large area thin film solar cells

The mapping capability of multichannel spectro-scopic ellipsometry (SE) has been demonstrated with examples from hydrogenated amorphous silicon (a-Si:H) and CdTe thin film photovoltaics (PV) technologies on glass. Maps as large as 40 x 80 cm2 have been obtained. For a-Si:H, maps of the bulk i-layer thickness and band gap as well as surface roughness layer thickness have been determined. For CdTe, a map of the CdS window layer thickness has been determined with the prospect of grain structure mapping. In both cases, maps of the thickness and properties of the underlying transparent conducting oxide (TCO) layers have been determined. These first results demonstrate the ability of mapping SE to guide scale-up of thin film PV deposition processes.