Combined Raman scattering, X-ray fluorescence and ellipsometry in-situ growth monitoring of CuInSe2-based photoabsorber layers on polyimide substrates

The combination of Raman scattering, X-ray fluorescence, and spectroscopic ellipsometry is presented as a new approach for in-situ optical monitoring of multinary semiconductor thin film growth. Our setup allows to determine phonon modes, chemical composition, the fundamental band gap energy, and the absorption coefficient of the semiconductor material immediately during the growth. We demonstrate our new approach exemplarily for CuInSe2, a multinary alloy with complex phase diagram. Process monitoring was performed on solar cell absorber layers deposited on flexible substrates in a roll-to-roll process.