We conduct a comparative study mainly on two types of nc-Si based solar cell structures, a-Si/a-SiGe/nc-Si triple-junction and a-Si/nc-Si double-junction. We have attained comparable initial efficiency for the both solar cell structures, 10.8∼11.8% initial total area efficiency (85 - 95W over an area of 0.79 m2). For better compatibility to our installed manufacturing equipment, we deposit a-Si and a-SiGe component cells with the existing deposition machines. Only nc-Si bottom component cells are prepared in separate deposition machines tailored for nc-Si process. Material properties of nc-Si and TCO films are also studied by Raman spectra, SEM, and AFM.