Thin silicon layers on Al2O3 for solar cells

For the fabrication of a thin film silicon solar cell the surface of an Al2O3 ceramic substrate has been inspected. It consists of small crystals with a maximum grain size of 5 μm. On this surface thin layers of silicon have been deposited. The surface of a 40 μm thick layer shows polycrystalline quality and grain sizes in the order of 10 μm. For the preparation of a thin film silicon solar cell a 5 μm p+-type layer of silicon has been deposited on an Al2O3 substrate. Additionally, a layer of a 20 μm p-type silicon has been deposited to act as the base of the thin film solar cell. This structure has been processed in a two mask process to a solar cell. From the measurement of the spectral response a diffusion length of 8 μm can be extracted. Preliminary results of an open-circuit voltage of about 0.1 V and a short-circuit current of about 8 mA have been measured for the solar cell with an area of 1×1 cm2.