Structural Characterization of Microcrystalline Silicon Solar Cells Fabricated by Conventional RF-PECVD

Direct structural characterization of single junction p-i-n type μc-Si: H solar cells prepared in a single chamber, batch process type KF-PECVD system has been carried out using Raman scattering, XRD, and AFM. The overall degree of microcrystallinity of μc-Si:H i-layers is presented in terms of the ratio of peak intensities (Ic/Ia) of Raman shift at around 520 cm^-1 and 480 cm^-1, respectively. Strong correlations among device performance, i-layer structural properties, and uniformity have been established using information provided by such direct characterization. Our data support the notion that stable, high quality μc-Si i-layers are grown near the 'edge' of microcrystalline-to-amorphous phase transition. Solar cells made from such optimal areas exhibit moderate microcrystallinity (moderate Ic/Ia values). Preferential orientation corresponding to Si (220) planes was observed on those optimal solar cells, which also exhibit less-regular surface morphologies and lower surface roughness compared to that observed on solar cells with mixed-phase or highly crystalline Si:H i-layers.