Design and verification of a pecvd fabricated multi-layer nano-scale photovoltaic device

This paper summarizes the results of computational and experimental studies of an enhanced thin film solar structure. The cell structure consists of a reflective aluminum layer beneath an 80nm absorbing layer of amorphous silicon, coated with a top layer of transparent and conductive indium tin oxide (ITO). The structure is mounted on a glass substrate. We first use constrained optimization techniques along with numerical solvers of the electromagnetic equations to specify the layer thicknesses of the design for maximized efficiency. Numerical analysis suggests that solar absorptivity in the thin film silicon can be enhanced by a factor of 2. The proposed design is then fabricated using Plasma Enhanced Chemical Vapor Deposition techniques, along with a control sample of bare silicon absorber for comparison. AFM imaging and spectrophotometry experiments are applied to estimate the realized thin film dimensions, deposition error, unwanted oxidation volume and the resulting reflectivity spectra. Comparisons of the measured and simulated reflectivity spectra of the fabricated cells, as well as Monte Carlo simulations based on incorporating random geometry errors in the numerical simulations suggest that the measured spectra are in accordance with the expected curves from simulations.