Hydrogen transformations in Si-based solar structures studied by precise FTIR spectroscopy

In this work, an attempt to clarify the origin of a very pronounced effect of the minority carrier lifetime evolution in SiNx:H/a-Si:H/Si/a-Si:H/SiNx:H and a-Si:H/Si/a-Si:H solar cell structures prepared at temperatures around 200 °C upon heat treatments in the temperature interval of 445–550 °C is performed. For a comparison, heavily hydrogenated Si substrates were investigated as well. Analysis of all structures studied was performed by means of precise FTIR measurements and quasi-steady-state photoconductance (QssPC) techniques. Annealing-induced transformations of hydrogen-related states in Si-based structures upon heat treatments were monitored by a FTIR system with an enhanced sensitivity. Strong monotonic decrease of the intensity of various Si–H and N–H stretching bands was observed in all types of H-containing layers upon heat treatments applied. It is concluded that the transformations of H-related complexes in all structures studied are responsible for the observed changes in passivation efficiency of a-Si:H and SiNx:H/a-Si:H layers.