Low-energy H2+ implantation effects on the characteristics of polysilicon solar cells

Low-energy H2+ ions were implanted into polysilicon solar cells to passivate the electrically active centers which existed in grains and grain boundaries. The illuminative and dark characteristics of solar cells were significantly improved. Measurements of the optical properties of monosilicon samples showed that the refractive index n was decreased after H2+ bombardment, and the value of the optical band gap Eg was increased from 1.1 eV of monosilicon to 1.3 eV. A thermal stability test was performed after hydrogenation. The refractive index n of hydrogenated samples rose again after annealing above 300degC, but the absorption coefficient α did not change significantly, even after annealing at 900degC for 30 min. (orig.)