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Realizing the potential of fluorine passivation for defects in silicon

This work explores the use of fluorine to passivate bulk defects in silicon. We present a simple method to incorporate fluorine atoms into the silicon bulk by annealing the sample with a thin thermally evaporated fluoride overlayer. It is found that fluorine incorporation can yield a comparable effect as hydrogenation, in passivating grain boundaries in mutlicrystalline silicon and reducing recombination strength of dislocation clusters in mono-like silicon. Moreover, we monitor the temperature dependence of the passivation reaction of hydrogenation and fluorination, using a micro-photoluminescence spectroscopy system with a temperature-controlled stage. It is found that the hydrogenation reaction occurs at the annealing temperature around 450 ° C, where a higher temperature above 500 ° C is required to activate the fluorination effect. The work provides new opportunities to improve solar cell performance.