Conductive guard rings for active pixel sensors

An array of active pixel sensors. The array of active pixel sensors includes a substrate that includes electronic circuitry. An interconnect structure is formed adjacent to the substrate. The interconnect structure includes a plurality of conductive vias. A plurality of conductive guard rings are formed adjacent to the interconnect structure. Each conductive guard ring is electrically connected to the substrate through at least one of the conductive vias. A plurality of photo diode sensors are formed adjacent to the interconnect structure. Each photo diode sensor is surrounded by at least one of the conductive guard rings. Each photo diode sensor includes a pixel electrode. The pixel electrode is electrically connected to the substrate through a corresponding conductive via. An I-layer is formed adjacent to the pixel electrode. The array of active pixel sensors further includes a transparent conductive layer formed adjacent to the photo diode sensors. An inner surface of the conductive layer is physically connected to the photo diode sensors, and electrically connected to the substrate through a conductive via. The electronic circuitry biases the photo diode sensors and controls a guard voltage potential of the conductive guard rings.