A solid state radiation imager includes a photosensor array having a plurality of pixels disposed on a substrate, each pixel having a respective photosensor coupled to a thin film transistor (TFT). The photosensor array further includes an opaque passivation layer that is disposed over non-photodiode areas of the photosensor array, including the TFT and address lines in the array. The opaque passivation layer has an absorbance that is greater than 1, and typically that is greater than 2. The opaque passivation layer further is typically made of a thermally stable polymer mixed with a light absorbing material such as an organic dye (e.g., Sudan Black B), carbon black, or graphite.