High-efficiency selenium-tellurium photodetector for direct-indirect dual layer detector

Dual-layer (DL) detectors offer the potential to generate highly informative images with a single-shot exposure. The Radiological Instrumentation Laboratory has been developing a direct/indirect conversion DL detector, focusing on high-resolution, high-sensitivity, large-area flat panel detectors (FPDs) to enhance material decomposition and reduce dose to the patient. Our work on the indirect conversion layer has led to the development of a selenium-tellurium photodetector that utilizes a silicon dioxide hole blocking layer. Single-pixel devices have shown external quantum efficiencies reaching a maximum of about 92% under 533 nm light, the limit that can be achieved due to reflection, scattering, and absorption from the substrate at that wavelength. This increases efficiency compared to the conventional FPD photodetector material of amorphous silicon by about 10%. Evaluation of the signal response shows high sensitivity to low light levels, stable signal output, and fast temporal recovery post-exposure. A large-area, pixelated FPD was fabricated following a similar architecture. MTF and DQE showed comparable performance to commercial a-Si based panels, indicating no degradation of performance from the Se-Te photodiode. The sensitivity of the Se-Te based panel surpassed that of a-Si when biased at moderate fields, with potential for even greater performance at higher fields. This shows promise for the development of a high-sensitivity indirect conversion panel for the photon-starved bottom layer of the dual-layer detector.