The present invention relates to a thin film solar cell and manufacturing method thereof. The thin film solar cell comprises a substrate, a front electrode layer, an absorber layer and a rear electrode layer stacked in such sequence, wherein the front electrode layer is formed by doping group III element into a zinc oxide. The thin-film solar cell further comprise an interlayer disposed between the front electrode layer and the absorber layer wherein the interlayer has p-type holes formed by introducing nitrogen-based gas having Argon (Ar) as a carrier gas interacted with the group III element by using PECVD or thermal treatment, implementation and diffusion on the front electrode layer surface so that the concentration of nitrogen atoms in the interlayer is greater than 1015/cm3.