In certain embodiments, an apparatus for down-converting and detecting photons includes a detector layer and a nanocrystal layer. The nanocrystal layer includes nanocrystals operable to absorb first photons of a higher energy and emit second photons of a lower energy in response to the absorption. The detector layer is configured to detect the second photons. In certain embodiments, a method for manufacturing an apparatus for down-converting and detecting photons includes preparing an outer surface of a substrate. Nanocrystals are disposed outwardly from the outer surface. The nanocrystals are operable to absorb first photons of a higher energy and emit second photons of a lower energy in response to the absorption.