The present disclosure, in some embodiments, relates to a CMOS image sensor. The CMOS image sensor has an image sensing element disposed within a substrate. A plurality of isolation structures are arranged along a back-side of the substrate and are separated from opposing sides of the image sensing element by non-zero distances. A doped region is laterally arranged between the plurality of isolation structures. The doped region is also vertically arranged between the image sensing element and the back-side of the substrate. The doped region physically contacts the image sensing element.