Real-time monitoring and process control in amorphous/crystalline silicon heterojunction solar cells by spectroscopic ellipsometry and infrared spectroscopy

In amorphous/crystalline silicon heterojunction solar cells, we have performed real-time thickness control of hydrogenated amorphous silicon (a-Si:H) layers with a precision better than +/- 1 Angstrom by applying spectroscopic ellipsometry (SE). A heterojunction solar cell fabricated by this process shows a relatively high conversion efficiency of 14.5 %. At the amorphous/crystalline interface, however, infrared attenuated total reflection spectroscopy (ATR) revealed the formation of a porous a-Si:H layer with a large SiH2-hydrogen content of 27 at. %. Based on SE and ATR results, we discuss the growth processes and structures of a-Si:H in heterojunction solar cells. (C) 2005 American Institute of Physics.