Direct-conversion imaging panel having a charge transport layer with controlled time constant

Direct conversion imaging panels have pixels that need to be protected from excessive voltage across the FET switch resulting from excess X-ray exposure. Protection can be achieved by placing a dielectric layer between the charge generator and the high voltage bias electrode. The charges that accumulate at the interface create a counter electric field so that the electron-hole pairs recombine in the selenium, thus limiting the charge accumulated at the corresponding pixels. A variety of means have been used to neutralize the charges accumulated at the interface, a so called erase step. We have demonstrated a novel charge transport layer (CTL) that protects the FETs from transient overexposure and eliminates the need for a separate erase step. By selection of the time constant of the CTL, the panel can be used for static and dynamic imaging. The operating principle of this new structure and the performance of prototypes compared to conventional will be reported.