Contatto di riferimento: Laura Basiricò
Partecipanti: Laura Basiricò
The main limitations of traditional inorganic materials for direct, solid-state detectors such as silicon, cadmium zinc telluride (CZT) or mercury iodide (HgI2), are the difficulty to process into large-area detector matrices, the stiff mechanical properties and high costs.
Several applications, as cultural heritage preservation, citizens’ security and medical diagnostics, require thin, conformable sensor panels, for a large-area determination of the incoming radiation dose.
Therefore, there is a huge interest on the development of a new generation of ionizing radiation sensors combining ease of processing, low power supply and mechanical flexibility.
In this framework, organic small molecules are the suitable candidates for this purpose for their excellent solubility in several common organic solvents and their processability at low temperature (<100°C), which allow to employ thin plastic flexible foils as substrates.
Among the organic devices, Organic Thin Film Transistors (OTFTs) are widely used for sensing application for several reasons: first they are multiparametric devices, in which different electronic parameters, can be extracted from their electrical characterization, offering the possibility of using a combination of variables in order to characterize their response to the parameter to be sensed, second, in OTFTs the electrical response can be intrinsically amplified by the transistor itself; third, OTFTs join the sensing properties with the switching features of a transistor, allowing the fabrication of sensors matrices in which every single element can be addressed without additional devices. Here we reported about the employment of OTFTs, fabricated onto flexible plastic substrates and operating at low voltages, as X-rays detectors.
We found that not only the signal amplitude, but also the X-rays sensitivity of the detector can be easily tuned through the field effect, reaching values up to 2400 nC/Gy (higher of three orders of magnitude than polymeric radiation detectors reported in literature).
Furthermore, a study on the reliability of the detector has been carried on, investigating the environment and aging impact on the transistor performances and exploring different strategies for device encapsulation and their impact on the radiation detection.