Organic Semiconducting Single Crystals as Next Generation of Low‐Cost, Room‐Temperature Electrical X‐ray Detectors

Abstract

Direct, solid-state X-ray detectors based on organic single crystals are shown to operate at room temperature, in air, and at voltages as low as a few volts, delivering a stable and reproducible linear response to increasing X-ray dose rates, with notable radiation hardness and resistance to aging. All-organic and optically transparent devices are reported.

Toward Low‐Voltage and Bendable X‐Ray Direct Detectors Based on Organic Semiconducting Single Crystals

“…[ 11,12 ] State-of-the-art solid state X-rays detectors are based on inorganic materials (such as silicon, cadmium, zinc, telluride, and diamond), and offer top detecting performances. However, they are rigid, heavy, and they require expensive growth facilities.…”

Organic Single Crystals: An Essential Step to New Physics and Higher Performances of Optoelectronic Devices

“…) for both holes [ 7,18,21,35 ] and electrons; [ 27,36 ] (b) reproducible observation of a bandlike transport and intrinsic mobility anisotropy in a number of systems, [24][25][26][27][35][36][37][38] signifying that charge delocalization in van der Waals crystals is indeed possible, and the transport regime not dominated by static disorder can be achieved; (c) the discovery of new types of conducting and even metallic interfaces; [39][40][41] (d) observation of a long-range (1-10 µm) diffusion of mobile triplet excitons in high-quality organic crystals, as well as non-linear regimes in photoconductivity with nontrivial set of power exponents (1, 1/2, 1/3, and 1/4) due to singlet fi ssion, triplet fusion and interaction of mobile excitons with charge carriers; [28][29][30][31] (e) realization of ionic-liquid gated single-crystal devices; [ 42,43 ] (f) realization of solid-state ionizing radiation sensors based on solution-grown organic crystals; [44][45][46][47][48] (g) development of fl exible single-crystal devices suitable for the studies of electromechanical properties of organic semiconductors; [ 22,49,50 ] (h) realization of extremely high current density in organic light-emitting transistors; [ 51 ] (i) study of electrical magnetochiral anisotropy in a bulk chiral molecular conductor; [ 52 ] (j) elucidation of the role of dimensionality on Beatrice Fraboni received an MPhil in microelectronics from the University of Cambridge, UK, and a PhD in Physics from the University of Bologna, Italy. In 2000 she joined the Faculty of Physics at the University of Bologna where she is presently a professor in condensed matter physics.…”

Charged-particle spectroscopy in organic semiconducting single crystals

“…This material showed greater stability in air than polyacetylene, but it exhibited limited detection efficiency and no spectroscopy grade performance. 9 Among organic materials, Organic Semiconducting Single Crystals (OSSCs) have been recently proven to be rather robust to environmental conditions (air, light, humidity), 10 and to have unique transport properties, due to their high chemical purity and lack of grain boundaries typical of polymeric films. In particular, they exhibit charge transport anisotropy, 11 high charge carrier mobility if compared to organic thin films (the highest reported among organic materials, up to 20 cm 2 /V s for rubrene single crystal-based transistors 12 ), and long exciton diffusion lengths, up to 8 lm, 13 a very high value compared to the 10 nm reported for organic thin-film photovoltaic devices.…”

“…These detectors are able to operate in ambient atmosphere, environmental light, and room temperature, providing a stable, linear photocurrent response with increasing dose rate and very good radiation hardness properties. 10,15 Considering these promising results in X-ray sensing and the above described unique properties of OSSCs, their further exploitation in charged-particle detection (i.e., alpha and beta radiation) appears to be extremely interesting. In addition, OSSC detectors have the potential to be used as fast neutron solid-state detectors, due to the high number of proton recoil events within hydrogen-rich organic molecules.…”

“…Moreover, we decided to test self standing mm-sized 4HCB crystals for alpha detection, because an alternative process which is able to deliver large area crystals, i.e., inkjet printing of solutions from which the crystals can grow, is still under optimization. Importantly, 4HCB single crystals already demonstrated interesting photocurrent detection performances 10 and optimized charge collection efficiency 19 under X-ray irradiation. We exploited the already studied anisotropy of 4HCB single crystals (electrical transport 17 and X-ray response 15 ) considering both a coplanar and a sandwich electrodes configuration, addressing the planar and the vertical crystallographic axes, respectively.…”