An alloyed a-Se-Te indirect flat panel imager for improved performance in a dual-layer x-ray detector

Dual-layer detectors offer the potential for energy separation, allowing for lesion differentiation and material decomposition without the effects of motion blur that occur in dual-energy detection. We have proposed a direct/indirect dual-layer amorphous selenium (a-Se) detector, in which the direct conversion top layer absorbs low energy X-rays and higher energy X-rays pass through to be absorbed by the indirect conversion bottom layer. First studies of the indirect layer, consisting of a thin-film transistor (TFT) flat panel detector (FPD) with an a-Se photoconductive layer, show promising results, but the MTF was limited by the performance of the gadolinium oxysulfide scintillator used. To improve spatial resolution, a CsI:Tl scintillator should be employed. Unfortunately, the emission peak of CsI:Tl scintillators falls outside optimal wavelengths for a-Se photoconduction. By alloying the a-Se with Te and operating at high fields, we improve absorption and signal production in the FPD. In this work, this is we fabricate single pixel a-Se-Te detectors with a parylene blocking layer and give results for Te concentrations of 0%, 10%, 15%, and 20%. While leakage currents and lag increase with Te content, conversion efficiency is improved by over 30%, showing promise for implementation into an FPD with a CsI:Tl scintillator.