Fullerene conjugated polymer based Bulk hetero-junction solar cell has been widely used over the last decade. and a lot of attention has been focused on engineering the properties of these system. there are varios methods to enhance power conversion efficiency like thermal anneling, surface patterning, optical spacer and co-solvent etc. In this study, regular nano pattern is successfully introduced on ther surface of active layer using simple soft lithography methods. It has been already reported that surface nano pattern can enhance the PCE of solar cell via scattering effect. but the change of phase separation and orientation of polymer chain during nano pattern was not fully understood. so In this work, surface nano pattern was introduced by different patterning methods ( thermal and solvent assisted molding ) then we investigated the phase separation and crystal orientaion using various characterization methods.