Optics of textured amorphous silicon surfaces

We have performed real time Stokes vector spectroscopy (also called polarimetry) during the preparation of hydrogenated amorphous silicon (a-Si:H) p–i–n solar cells on textured tin-oxide (SnO2) surfaces. With this spectroscopy (1.5–4.0 eV), the irradiance, Ir, and polarization parameters, {(Q,χ),p}, for the specularly reflected beam are obtained with 0.8 s resolution versus time during solar cell preparation. Here Q and χ are the tilt and ellipticity angles of the polarization state, respectively, and p is the degree of polarization. From an analysis of these spectra, we establish a model for textured a-Si:H intrinsic-layer growth that includes both microscopic and macroscopic structural components. Using such a model, the evolution of structural and optical properties of the solar cell components can be determined, and the results provide realistic inputs for optical modeling of solar cells.