A photodetector has a photoactive layer of semiconducting inorganic nanoparticles positioned between a hole transport electron blocking layer of a first metal oxide and an electron transport hole blocking layer of a second metal oxide. The nanoparticles are responsive to electromagnetic radiation in at least the infrared region of the spectrum. The first metal oxide can be NiO, and the second metal oxide can be ZnO or TiO2. The metal oxide layers render the photodetector stable in air, even in the absence of an encapsulating coating around the photodetector. The photodetector has a P-I-N structure.