high atomic number (z) polycrystalline and amorphous photoconductors are currently being investigated to extend direct conversion x-ray detectors to real-time and high-energy lowdose applications. amorphous lead oxide (a-pbo) is one of the most promising photoconductor candidates because of its negligible signal lag and high theoretical x-ray conversion efficiency. however, a-pbo layers are still experimental; pbo technology has been developed to the point where material science and engineering approaches must be applied to make a-pbo detector prototypes suitable for low-dose x-ray imaging. this includes determining the most appropriate a-pbo multilayer detector structures with specially designed blocking layers that will withstand the high electric fields needed for efficient (i.e., complete) collection of x-ray generated charge while maintaining an acceptable dark current (dc) level. dc is a source of noise in the detector structure that degrades the signal-to-noise ratio (snr) of the detector system in low-exposure applications. here we investigate the use of polyimide (pi) as a hole-blocking layer. pi blocking layers were proven successful in the only commercially used direct conversion detectors, which are based on layers of photoconductive amorphous selenium (a-se). experimentally, pi was shown to have the most suitable electrical and physical properties for our a-pbo technology. in addition, pi has a straightforward application process of spin coating. therefore, pi was chosen as a hole blocking layer to decrease dc to tolerable levels in an a-pbo-based detector. [...]