Extrinsic passivation of silicon surfaces for solar cells

In the present work we study the extent to which extrinsic chemical and field effect passivation can improve the overall electrical passivation quality of silicon dioxide on silicon. Here we demonstrate that, when optimally applied, extrinsic passivation can produce surface recombination velocities below 1.2 cm/s in planar 1 Omega cm n-type Si. This is largely due to the additional field effect passivation component which reduces the recombination velocity below 2.13 cm/s. On textured surfaces field effect passivation has a comparable effect, and surface recombination velocities below 32 cm/s are achieved when field effect passivation is optimised extrinsically. Modelling of interdigitated back contact cells showed an absolute increase in efficiency of 0.1 % when passivation was optimised via extrinsic dielectric charge. These results point to the importance extrinsic passivation will have for future dielectric coatings used in solar cell manufacture.