The present approach involves a radiation detector module with increased quantum efficiency and methods of fabricating the radiation detector module. The module includes a scintillator substrate and a photodetector fabricated on the scintillator substrate. The photodetector includes an anode, active organic elements, and a cathode. The module also includes a pixel element array disposed over the photodetector. During imaging, radiation attenuated by an object to be imaged may propagate through the pixel element array and through the layers of the photodetector to be absorbed by the scintillator which in response emits optical photons. The photodetector may absorb the photons and generate charge with improved quantum efficiency, as the photons may not be obscured by the cathode or other layers of the module. Further, the module may include reflective materials in the cathode and at the pixel element array to direct optical photons towards the active organic elements.