An Engineering of Multilayered Lead Oxide Photoconductor for Lag-free X-ray Digital Detector

Lead Oxide is one of the most promising photoconductors for direct conversion X-ray medical imaging detectors. It has two polymorphic forms - polycrystalline and amorphous, that have their own distinctions. Polycrystalline Lead Oxide (poly-PbO) has a long history of application in optical imaging, in so-called "Plumbicon video pick-up tubes", but it is inapplicable for real-time X-ray imaging due to significant signal lag that makes temporal performance inadequate. Recently synthesized Amorphous Lead Oxide (a-PbO) photoconductor is essentially lag-free. Here we report on our approach to combine a thin layer of a-PbO with a thick layer of poly-PbO for lag-free X-ray operation. Transport properties of a-PbO/poly-PbO bi-layered structure were characterized by photo-Charge Extraction by Linearly Increasing Voltage technique. Experimentally measured temperature and electric field dependencies of the hole's mobility suggest a highly dispersive transport with the magnitudes of hole's mobilities similar to a-Se - currently the only commercially viable photoconductor for the direct conversion X-ray detectors. A response to X-ray irradiation shows no image lag, allowing operation of the detector in real-time imaging.