Real Time Optics of the Growth of Textured Silicon Films in Photovoltaics: Final Technical Report, 1 August 1999--12 August 2002

Novel optical instruments, including single and dual rotating-compensator multichannel ellipsometers, have been designed and developed to probe the evolution of the microstructure, spectroscopic optical properties, and other materials characteristics during the fabrication and processing of individual thin films and thin-film structures used in photovoltaic devices. These instruments provide afoundation for next-generation process design/control and metrology in existing and future photovoltaics technologies. In this project, the materials system studied in the greatest detail was thin-film silicon, fabricated at low temperatures by plasma-enhanced chemical vapor deposition. Real-time measurements of such thin films by multichannel ellipsometry have established deposition phasediagrams that provide guiding principles for multistep fabrication of high-performance amorphous (a-Si:H) and microcrystalline (mc-Si:H) solar cells. Such phase diagrams have also served to disprove conventional wisdom in the fabrication of thin-film solar cell structures, thus avoiding future unproductive research efforts.