Among other things, one or more image sensors and techniques for forming such image sensors are provided. An image sensor comprises a photodiode array configured to detect light. A filler grid is formed over the photodiode array, such as over a dielectric grid. The filler grid comprises one or more filler structures, such as a first filler structure that provides a light propagation path to a first photodiode that is primarily through the first filler structure. In this way, signal strength decay of light along the light propagation path before detection by the first photodiode is mitigated. The image sensor comprises a reflective layer that channels light towards corresponding photodiodes. For example, a first reflective layer portion guides light towards the first photodiode and away from a second photodiode. In this way, crosstalk, otherwise resulting from detection of light by incorrect photodiodes, is mitigated.