A photodetector includes one or more photodiodes and a signal processing circuit. Each photodiode includes a transparent first electrode, a second electrode, and a heterojunction interposed between the first electrode and the second electrode. Each heterojunction includes a quantum dot layer and a fullerene layer disposed directly on the quantum dot layer. The signal processing circuit is in signal communication each the second electrode. The photodetector may be responsive to wavelengths in the infrared, visible, and/or ultraviolet ranges. The quantum dot layer may be treated with a chemistry that increases the charge carrier mobility of the quantum dot layer.