Sensitivity analysis of X-ray detectors based on BFE and MEH-PPV organic sensor

In this work we fabricated flexible cells of organic devices in which layers of poly [9,9′-dioctyl-fluorene-2,7-diyl]-co-poly[diphenyl-p-tolyl-amine-4,4′-diyl] (BFE) and poly[1-methoxy-4-(2-ethylhexyloxy)-phenylenevinylene] (MEH-PPV) were deposited on Indium Tin Oxide (ITO) coated Polyethylene terephtalate (PET) substrates. In addition to investigating MEH-PPV organic sensors, this research has introduced a novel X-ray detector based on BFE organic sensor. BFE hasn't been applied in X-ray sensors and in this paper we use this organic material to fabricate a new electronic device. Devices were being exposed to X-ray source which normally operates at 60kV or 70kV for medical applications. Device fabrication followed a planar structure in which a thick layer of polymer was sandwiched between two metal electrodes. Based on experiments performed at room temperature, we found out that BFE-based structure proves to be much more stable in comparison to its MEH-PPV-based counterpart. It also maintained almost the same photocurrent in a four months time frame after fabrication. The operation mechanism of the device is described by photoconductive phenomenon of X-ray detectors based on organic materials. The response time of the device is 53ms. All photocurrent measurements were done under the application of a 170 kV/cm electric field. Corresponding results indicated that Al/BFE better contributes to the formation of a rectifying contact than that of Al/MEH-PPV. Utilization of BFE in organic sensor fabrication generated such electronic devices that don't have the weaknesses of RVG (radiovisiography) silicon sensors (i.e. inflexibility, instability against moisture) and could be very helpful in medical radiography applications.