Flexible radiation dosimeters have been produced incorporating thick films (>1 μm) of the semiconducting polymer
poly([9,9-dioctylfluorenyl-2,7-diyl]-co-bithiophene). Diode structures produced on aluminium-metallised poly(imide)
substrates, and with gold top contacts, have been examined with respect to their electrical properties. The results suggest
that a Schottky conduction mechanism occurs in the reverse biased diode, with a barrier to charge injection at the
aluminium electrode. Optical absorption/emission spectra reveal a band gap of 2.48 eV for the polymer. The diodes have
been used for direct charge detection of 17 keV X-rays, generated by a molybdenum source. Using operating voltages of
-10 and -50 V respectively, sensitivities of 54 and 158 nC/mGy/cm3 have been achieved. Increasing the operating
voltage shows that the diodes are stable up to approximately -200 V without significant increase in the dark current of
the device (<0.2 nA).
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