Towards industrial deposition of metal oxides for passivating and carrier selective contacts: MoO_x deposited by industrial size reactive DC magnetron sputtering and industrial size linear evaporation source

摘要

Passivating contacts are considered as a possibility to enhance silicon based PV performance due to lower interface recombination rates of charge carriers. Most of the investigation on metal oxide based contacts so far was done in laboratory scale. Mass production requires the scale-up of the processes. This contribution reports on first deposition experiments of MoO_x hole selective contacts by industrial size reactive magnetron sputtering and thermal evaporation. Reactive sputtering was carried out on a vertical inline tool equipped with a rotatable target of 1 m length. Thermal evaporation was conducted with a linear evaporation source of 46 cm length. Films were deposited on solar cell precursors in order to estimate charge carrier selectivity and band bending induced into the c-Si wafer by the MoO_x based hole contact. First results show that the selectivity, band bending, and optical transmission of reactively sputtered MoO_x films depend on the working point of the reactive sputter process. However, the selectivity still is far from what was reached in small-scale evaporation experiments. Films deposited with the industrial linear evaporation source show much better selective properties even comparable to lab-scale evaporation. Based on these results there seems to be a high potential to transfer the small scale laboratory evaporation process to larger areas in dynamic deposition, but further work is needed to tailor the properties of the sputter deposited MoO_x.