Abstract: A method for manufacturing an active layer of a solar cell is disclosed, the active layer manufactured including multiple micro cavities in sub-micrometer scale, which can increase the photoelectric conversion rate of a solar cell. The method comprises following steps: providing a substrate having multiple layers of nanospheres which are formed by the aggregated nanospheres; forming at least one silicon active layer to fill the inter-gap between the nanospheres and part of the surface of the substrate; and removing the nanospheres to form an active layer having plural micro cavities on the surface of the substrate. The present invention also provides a solar cell comprising: a substrate, an active layer, a transparent top-passivation, at least one front contact pad, and at least one back contact pad. The active layer locates on a surface of the substrate and has plural micro cavities whose diameter is less than one micrometer.