Spectral response tuning of organic photodetectors using strong microcavity effects for medical X-ray detector application

An X-ray detector system was fabricated with an organic small molecule photodetector and a terbium-doped gadolinium oxysulfide (Gd2O2S:Tb) scintillating screen. Though the microsphere cluster structure of the Gd2O2S film had advantage in low material cost, wavelength matching to the proper photodetector is challenging due to its scintillating performance property in the relatively narrow emission spectrum range. To tune the absorption spectrum of the organic photodetector to that of the emission spectrum of the Gd2O2S, a microcavity effect was applied by controlling the thickness of the C-60 layer. The peak wavelength of the absorption spectrum was tuned over a broad region of wavelengths, from 461 nm to 776 nm. The fabricated X-ray detector system was demonstrated in a medical X-ray radiography system.