THE ROLE OF PHASE TRANSITIONS BETWEEN AMORPHOUS AND MICROCRYSTALLINE SILICON ON THE PERFORMANCE OF PROTOCRYSTALLINE Si:H SOLAR CELLS

A systematic study has been carried out to quantify the effect of microcrystallite nucleation in the intrinsic layer of protocrystalline Si:H p-i-n solar cells prepared by rf plasma enhanced chemical vapor deposition (PECVD). Real-time spectroscopic ellipsometry (RTSE) results that have previously identified the transitions from amorphous to microcrystalline phase were confirmed with atomic force microscopy (AFM) images. The effects of the phase transitions in the bulk intrinsic layer, as well as near the p/i interface of p-i-n cells, have been evaluated as a function of film thickness and H2-dilution ratio (R=[H2]/[SiH4]). Illuminated and dark J-V characteristics are correlated with the microstructural evolution of the Si:H films yielding insight into the “sharpness” of the transition. Evidence of abrupt changes in the mobility gap is obtained from the selfconsistent numerical modeling of cell characteristics.