Medical devices with photodetectors and related systems and methods

In one aspect, a medical device may be configured to couple to a body, the medical device comprising: a substrate configured to couple to a user's skin; a photodetector comprising an array of quantum dots, wherein the array of quantum dots includes a first quantum dot of a first size and a second quantum dot of a second size, wherein the first size is different from the second size; a first illuminator configured to emit light at a first range of wavelengths; and a second illuminator configured to emit light at a second range of wavelengths. The second range of wavelengths may be different from the first range of wavelengths.