In various example embodiments, the inventive subject matter is an image sensor and methods of formation of image sensors. In an embodiment, the image sensor comprises a semiconductor substrate and a plurality of pixel regions. Each of the pixel regions includes an optically sensitive material over the substrate with the optically sensitive material positioned to receive light. A pixel circuit for each pixel region is also included in the sensor. Each pixel circuit comprises a charge store formed on the semiconductor substrate and a read out circuit. A non-metallic contact region is between the charge store and the optically sensitive material of the respective pixel region, the charge store being in electrical communication with the optically sensitive material of the respective pixel region through the non-metallic contact region.