Interface Structure in a-Si:H/c-Si Heterojunction Solar Cells Characterized by Optical Diagnosis Technique

We have characterized the interface structure of hydrogenated amorphous silicon (a-Si:H) p-i layers deposited on n-type crystalline silicon (c-Si) by applying real-time spectroscopic ellipsometry (SE) and infrared attenuated total reflection spectroscopy (ATR). By using SE, real-time thickness control of a-Si:H p-i layers in a-Si:H/c-Si heterojunction solar cells has been performed. We obtained a solar cell efficiency of 16.1 % at optimum p-i layer thicknesses of i/p=40/30 Aring without the incorporation of surface texture and a back-surface field (BSF) structure. Interface structures deduced from real-time diagnoses show clear correlation with the solar cell characteristics. In particular, we find that the epitaxial growth of thin Si layers on the c-Si substrates leads to a severe reduction in the solar cell performance