Exploration of Organic Electronics as Radiation Detectors

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This program will explore the use of organic electronics as radiation detection devices. In particular, organic field effect transistors (OFETs) will be the principal device of interest. Organic electronics have tremendous potential as radiation detectors for two important reasons. First, their chemical composition more closely resembles water than conventional, silicon-based electronics. This is critically important in the field of radiation dosimetry since estimates of energy deposition in the human body are routinely approximated by energy absorption in water. Second, the processes by which organic electronics are manufactured can be simpler, cheaper and more flexible than with conventional electronics. A completely organic radiation detector does not require silicon wafers, can employ simple manufacturing processes such as spin coating, can be deposited on flexible substrates and can be used across a wide spectrum of radiation types and energies without requiring recalibration (unlike any other conventional radiation detector). In this research program organic radiation detectors will be explored on multiple fronts. Monte Carlo simulations will be used to investigate the roles of detector chemical composition, as well as physical size and shape, on the energy-dependence of the devices as well as the perturbations introduced by the detector to the local radiation field. Chemical composition will be studied for the purpose of not only maximizing water-equivalence across as wide an energy range as possible, but also for the purpose of exploiting composition (i.e. through the inclusion of high atomic number materials) to permit energy spectrum mapping through the use of multiple detector arrays (i.e. multiple detectors with different energy sensitivities). Devices that are manufactured at McGill University (through a close collaboration with professor Dmytrii Perepichka in the Department of Chemistry) will be studied in detail with respect to their dependence on a number of variables, including: energy (~50 kVp - 18 MV photons), dose rate, temperature, applied bias, cumulative dose and directional response. They will also be studied with respect to other standard measures of detector performance such as linearity, reproducibility, stability etc. Basic research aimed at developing an understanding of the underlying mechanisms of signal generation in OFET radiation detectors will make use of various analytical techniques (i.e. UV, NMR, fluorescence and electron paramagnetic resonance spectroscopy). This research program will develop highly valuable skill sets in graduate students and provide valuable information on the radiation response of organic electronics that will be of tremendous benefit to not only Medical Physicists, but others working in fields such as space science and military applications.