Exceptional silicon surface passivation by an ONO dielectric stack

Immeasurably low surface recombination of crystalline-silicon wafers is demonstrated with an oxide-nitride-oxide (ONO) corona charged dielectric stack. We detail experimental variations to each layer of the dielectric stack to establish a procedure which provides outstanding passivation properties on textured and planar silicon wafers. We demonstrate surface recombination velocities of < 1 cm/s and surface recombination prefactors of < 1 fA/cm2, and we show that passivation remains stable over a 2-year period when stored in ambient conditions. The effective carrier lifetimes of n-type silicon are found to exceed the commonly accepted intrinsic lifetime limit, and in one case, a lifetime of 170 ms is attained. These high lifetimes indicate that ONO passivation is amongst the best dielectric passivation, and as such, might find applications in high-efficiency silicon solar cells.