A dual-energy x-ray detector includes a plurality of x-ray detector elements that detect x-rays that are generated by an x-ray source and that have passed through an object. Each of the x-ray detector elements includes a first scintillator layer adapted to convert x-rays from the x-ray source that have passed through the object into light of a first wavelength, and a second scintillator layer positioned behind the first scintillator layer and adapted to convert x-rays from the x-ray source that have passed through the object and through the first scintillator layer into light of a second wavelength. Each of the x-ray detector elements further includes a first optical sensor having a spectral sensitivity substantially matched to light of the first wavelength, and a second optical sensor having a spectral sensitivity substantially matched to light of the second wavelength.