High-Dose Radiation Effects In Organic Thin-Film Transistors
Abstract
Purpose
To assess the high-dose performance of organic thin-film transistors (OTFTs) for radiotherapy applications and to identify material-level effects impacting detector response.
Methods
OTFTs were irradiated to 1 and 2 kGy using a linear accelerator and device sensitivity was assessed over a 20 Gy range. Electrical characteristics, including voltage shift and field-effect mobility, were evaluated as a function of accumulated dose. To isolate material-level effects, organic materials used in the OTFTs (pentacene and polystyrene) were irradiated both separately and as a stacked structure representative of the device configuration, to 1 and 10 kGy using a Cobalt-60 source. X-ray photoelectron spectroscopy (XPS) was performed on pristine and irradiated samples to identify chemical changes following high-dose irradiation.
Results
The OTFT voltage exhibited a linear shift with accumulated dose over the 20 Gy range. Detector sensitivity remained unchanged within experimental uncertainty up to 2 kGy, while mobility decreased linearly by up to 12%. XPS analysis revealed an increase in carbon–oxygen functional groups in pentacene with increasing dose, indicating radiation-induced oxidation. In polystyrene, a shift in carbon peak binding energy was observed with dose, consistent with the formation of acceptor-like defects in the material. These changes in both materials explain the observed mobility degradation in the OTFTs.
Conclusion
This work demonstrates the potential of OTFTs as radiation dosimeters capable of retaining linearity and sensitivity after 2 kGy of dose, despite measurable degradation in charge transport properties. It also provides insight into the effects of ionizing radiation on organic materials, which can guide material and device optimization to improve radiation tolerance and long-term performance in organic electronic dosimeters. Further investigation at higher doses is required to determine when mobility degradation begins to adversely affect detector sensitivity.