Contatto di riferimento: Marta Tessarolo
Partecipanti: Dr. Andrea Ciavatti
The research interest on alternative materials for innovative ionizing radiation detection is rapidly growing. Traditional materials for direct, solid-state detectors (i.e. directly converting ionizing radiation into an electrical signal) such as silicon, cadmium zinc telluride (CZT) or mercury iodide (HgI2), suffer from severe limitations in their processing into large-area pixelated detector matrices.
A new generation of ionizing radiation sensors has to be envisaged, ideally combining ease of processing, low power supply and mechanical flexibility. Indeed, several applications, spanning from citizens’ security, to industrial and to medical diagnostics, require thin, conformable sensor panels, for a large-area determination of the incoming radiation dose and energy distribution. As such applications are of high commercial interest, intense efforts have been recently devoted to the realization of large-area direct detectors based on inorganic materials (e.g. amorphous Silicon, amorphous Selenium, Diamond), which, however, still share the constraints of expensive or complex growth techniques and maintain stiff mechanical properties.
Organic semiconductors combine efficient charge transport with low-temperature deposition and large-area processing on flexible substrates, making them a promising class of materials for the new generation of ionizing radiation detectors. We have recently demonstrated how solution-processed, flexible, organic thin film-based direct detectors can reach high sensitivity to X-rays thanks to a photoconductive gain effect. However, high-energy photon absorption is challenging, as organic materials are constituted of atoms with low atomic numbers. Three approaches are here reported to increase the X-ray sensitivity.
One is the development of a solution-processed organic thin-film based, fully flexible, direct X-ray detectors, with sensitivity values up to several hundreds of nC/Gy at ultra-low bias (0.2V) due to a photoconductive gain effect. The second approach is to blend organic material with high-Z nanoparticles (NPs) to obtain a high X-ray stopping power. Finally, hybrid organic-inorganic perovskites have been recently proposed as alternative materials for X- and γ-photon direct detection, thanks to their intrinsic high Z constituent atoms, e.g. Pb in lead halide perovskite, combined with a good charge mobility.