The application of organic electronic materials for the detection of ionizing radiations is very appealing thanks to their mechanical flexibility, low-cost and simple processing in comparison to their inorganic counterpart. In this work we investigate the direct X-ray photoconversion process in organic thin film photoconductors. The devices are realized by drop casting solution-processed bis-(triisopropylsilylethynyl)pentacene (TIPS-pentacene) onto flexible plastic substrates patterned with metal electrodes; they exhibit a strong sensitivity to X-rays despite the low X-ray photon absorption typical of low-Z organic materials. We propose a model, based on the accumulation of photogenerated charges and photoconductive gain, able to describe the magnitude as well as the dynamics of the X-ray-induced photocurrent. This finding allows us to fabricate and test a flexible 2 × 2 pixelated X-ray detector operating at 0.2 V, with gain and sensitivity up to 4.7 × 104 and 77,000 nC mGy−1 cm−3, respectively.

The recent years witnessed an unprecedented enhancement in improved functionality materials and in the sophistication of solution‐based device fabrication techniques. Such significant advancements lead to unexpected and effective opportunities for the utilization of solution‐grown organic materials and perovskites in the detection of ionizing radiation. This review presents an updated overview of the recently reported top performing and more innovative organic/perovskite‐based X‐ray detectors, providing a comparison and a critical discussion on the different materials’ properties and performance. Solution‐growth methods that allow to obtain detector grade electronic materials are discussed, focusing on the growth both of single crystals and of thin/thick films and foreseeing the implementation of large‐area, organic/hybrid‐, and perovskite‐based radiation detectors. Insights into the X‐ray detection mechanisms are provided, detailing the fundamental processes involved in the charge collection and in the photoconductive gain model, together with the typical figures of merit that describe radiation detector performance.

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.

Materials and technology development for designing innovative and efficient X-ray radiation detectors is of utmost importance for a wide range of applications ranging from security to medical imaging. Here, highly sensitive direct X-ray detectors based on novel cesium (Cs)-based triple cation mixed halide perovskite thin films are reported. Despite being in a thin film form, the devices exhibit a remarkably high X-ray sensitivity of (3.7 ± 0.1) µC Gy −1 cm −2 under short-circuit conditions. At a small reverse bias of 0.4 V, the sensitivity further increases by orders of magnitude reaching a record value of (97 ± 1) µC Gy −1 cm −2 which surpasses state-of-the-art inorganic large-area detectors (a-Se and poly-CZT). Based on detailed structural, electrical, and spectroscopic investigations, the exceptional sensitivity of the triple cation Cs perovskite is attributed to its high ambipolar mobility-lifetime product as well as to the formation of a pure stable perovskite phase with a low degree of energetic disorder, due to an efficient solution-based alloying of individual n-and p-type perovskite semiconductors.

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Organic semiconductor materials exhibit a great potential for the realization of large-area solution-processed devices able to directly detect high-energy radiation. However, only few works investigated on the mechanism of ionizing radiation detection in this class of materials, so far. In this work we investigate the physical processes behind X-ray photoconversion employing bis-(triisopropylsilylethynyl)-pentacene thin-films deposited by bar-assisted meniscus shearing. The thin film coating speed and the use of bis-(triisopropylsilylethynyl)-pentacene:polystyrene blends are explored as tools to control and enhance the detection capability of the devices, by tuning the thin-film morphology and the carrier mobility. The soobtained detectors reach a record sensitivity of 1.3 • 10 4 µC/Gy•cm 2 , the highest value reported for organic-based direct X-ray detectors and a very low minimum detectable dose rate of 35 µGy/s. Thus, the employment of organic large-area direct detectors for X-ray radiation in real-life applications can be foreseen.

The demand for high‐energy radiation detection systems combining high sensitivity, low‐cost and large‐area fabrication has pushed the research on hybrid perovskites as promising materials for X‐ and γ‐photon detection, thanks to their high Z atoms, solution‐processability, and high optoelectronic performance. Here, flexible direct X‐ray detectors are demonstrated with outstanding real‐time detection properties. They are based on printed micrometers‐thick films of methylammonium lead triiodide nanocrystals inks, formulated in low boiling point and benign solvents. Record optoelectronic performances, such as high X‐ray sensitivity (up to 2270 µC Gy−1 cm−2), radiation tolerance over 2.2 Gy of total dose, and fast response time (48 ms) have been achieved by using a simple device architecture and materials processing The functionality under strong bending stress (strain > 10%) and under high X‐ray energy (up to 150 keV) has been assessed, opening the way for flexible real‐time direct radiation detectors and imagers, operating at low‐voltages (bias < 4V) and apt to be fabricated by means of large‐area scalable processes.

The attention on the application of organic electronics for the detection of ionizing radiation is rapidly growing among the international scientific community, due to the great potential of the organic technology to enable large-area conformable sensor panels. However, high-energy photon absorption is challenging as organic materials are constituted of atoms with low atomic numbers.Here it is reported how, by synthesizing new solution-processable organic molecules derived from 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and 2,8-Difluoro-5,11bis(triethylsilylethynyl)anthradithiophene (diF-TES-ADT), with Ge-substitution in place of the Si atoms to increase the material atomic number, it is possible to boost the X-ray detection performance of organic thin films on flexible plastic substrates. TIPGe-pentacene based flexibleOTFTs show high electrical performance with higher mobility (0.4 cm 2 V -1 s -1 ) and enhanced X-ray sensitivity, up to 9.0 x 10 5 µC Gy -1 cm -3 , with respect to TIPS-pentacene based detectors. Moreover, similar results are obtained for diF-TEG-ADT devices, confirming that the proposed strategy, i.e.increasing the atomic number of organic molecules by chemical tailoring to improve X-ray sensitivity, can be generalized to organic thin film detectors, combining high X-ray absorption, mechanical flexibility and large area processing.