Abstract-A major problem of current silicon thin film solar cells lies in low carrier collection efficiency due to short carrier diffusion length. Instead of improving the collection efficiency in a relatively thick solar cell, increasing light absorption while still keeping the active layer thin is an alternative solution. In this paper, simultaneous absorption enhancement in a thin film Si solar cell by incorporating a 2D periodic metal nanopattern and by adding a frequency conversion was studied using three dimensional finite element analysis and experimental demonstration.