Thin film organic photodetectors for indirect X-ray detection demonstrating low dose rate sensitivity at low voltage operation

• Published in: Journal of applied physics 2017-12, Vol.122 (22)
• Main Authors: Starkenburg, Daken J., Johns, Paul M., Baciak, James E., Nino, Juan C., Xue, Jiangeng
• Format: Article
• Language: English
• Subjects: INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND TECHNOLOGY; MATERIALS SCIENCE
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/1.4999759

Developments in the field of organic semiconductors have generated organic photodetectors with high quantum efficiency, wide spectral sensitivity, low power consumption, and unique form factors that are flexible and conformable to their substrate shape. In this work, organic photodetectors coupled with inorganic CsI(Tl) scintillators are used to showcase the low dose rate sensitivity that is enabled when high performance organic photodetectors and scintillator crystals are integrated. The detection capability of these organic-inorganic coupled systems to high energy radiation highlights their potential as an alternative to traditional photomultiplier tubes for nuclear spectroscopy applications. When exposed to Bremsstrahlung radiation produced from an X-ray generator, SubPc:C60, AlPcCl:C70, and P3HT:PC61BM thin film photodetectors with active layer thicknesses less than 100 nm show detection of incident radiation at low and no applied bias. Remarkably low dose rates, down to at least 0.18 μGy/s, were detectable with a characteristic linear relationship between exposure rate and photodetector current output. These devices also demonstrate sensitivities as high as 5.37 mC Gy−1 cm−2 when coupled to CsI(Tl). Additionally, as the tube voltage across the X-ray generator was varied, these organic-inorganic systems showed their ability to detect a range of continuous radiation spectra spanning several hundred keV.