Toward Low-Voltage and Bendable Radiation Direct Detectors Based on Organic Semiconducting Single Crystals

In last years, Organic Semiconducting Single Crystals (OSSCs) exhibited the highest electrical performances among organic materials, thanks to their chemical purity and high symmetry.Therefore, high attention has been focused on the development of OSSCs-based devices. The possibility of covering large area with solution grown OSSCs by means of printing deposition techniques (e.g. inkjet printing), has been recently demonstrated[1], allowing the fabrication of very low-cost, large area devices exploitable for a wide range of applications. Among the others, the development of large-area ionizing radiation detectors with high resolution pattern in pixelated matrices, with each single pixel constituted by a OSSC is extremely appealing since no low-cost, large-area, conformable and tissue equivalent detectors are currently available.We reported how solution grown OSSCs provide a direct, stable, and linear electrical photoresponse to increasing X-rays dose rates, proving to be good ionizing radiation sensors operating at room temperature[2,3]. A dedicated study of the collecting electrodes geometry, crystal thickness and interaction volume allowed us to maximize the charge collection efficiency and sensitivity, thus assessing how even few micrometers thick OSSCs can perform at low operating voltages on PET flexible substrates. We have also investigated the ability of OSSCs to be employed as detectors of charged particles radiation in pulse mode operation, with very good detection efficiency and peak discrimination, and the extraction of the µτ value. Furthermore, the development of charged-particles detection is encouraging for their further exploitation in the detection of neutrons, that strongly interact within hydrogen-rich organic molecules.[1]H.Minemawari, Nature,475,364-367(2011).[2] B. Fraboni et al., Adv. Mat., 24, 17, 2289( 2012) [3] A.Ciavatti et al., Adv. Mater. 27, 44, 7213 (2015)