2D layered hybrid perovskites have recently attracted an increasing interest as active layers in LEDs and UV–Vis photodetectors. 2D perovskites crystallize in a natural self‐assembled quantum well‐like structure and possess several interesting features among which low‐temperature (<100 °C) synthesis and low defect density. Here are presented solid‐state ionizing radiation direct detectors based on the 2D layered hybrid perovskite PEA₂PbBr₄ (PEA = C₆H₅C₂H₄NH₃⁺) deposited from solution using scalable techniques and directly integrated onto a pre‐patterned flexible substrate in the form of micro‐crystalline films displaying crystal‐like behavior, as evidenced by the ultra‐fast (sub‐microsecond) and good detection performances under UV light. The effective detection of X‐rays (up to 150 kVp) is demonstrated with sensitivity values up to 806 µC Gy⁻¹ cm⁻² and Limit of Detection of 42 nGy s⁻¹, thus combining the excellent performance for two relevant figures of merit for solid‐state detectors. Additionally, the tested devices exhibit exceptionally stable response under constant irradiation and bias, assessing the material robustness and the intimate electrical contact with the electrodes. PEA₂PbBr₄ micro‐crystalline films directly grown on flexible pre‐patterned substrate open the way for large‐area solid‐state detectors working at low radiation flux for ultra‐fast X‐ray imaging and dosimetry.

High sensitivity and efficient X‐ray detectors are needed to promote and boost their application as tools in medical diagnostics and radiotherapy. Lead halide perovskites have emerged recently as a novel class of material for efficient X‐ray detection. Although 3D perovskites possess very interesting optoelectronic properties they suffer from low environmental and operational stability. Here a strategy based on using starch as a polymeric template for the fabrication of stable thin film perovskite X‐ray detectors is reported. The proposed p‐i‐n photodiodes can operate with no external bias applied (fully passive devices), reaching a top sensitivity of 5.5 ± 0.2 µC Gy⁻¹ s⁻¹. The device degradation is monitored for samples stored in air for a time window of 630 days, demonstrating exceptional stability: 97% of the initial sensitivity is retained for the best perovskite‐starch composite formulation making it the most stable unencapsulated perovskite X‐ray detector reported so far.

On‐line in situ monitoring of radiation emitted by radiotracers during intravenous injection is of crucial importance for the safety of patients and personnel involved in nuclear medicine treatments and analysis. The aim of this work is to assess wearable perovskite ionizing radiation detectors for such application. With this purpose pixelated direct detector based on thin films of 2D layered perovskite PEA ₂ PbBr ₄ are tested for the monitoring of gamma‐rays emitted by ¹⁸ F radiopharmaceutical under different experimental conditions. The wearable detector is here demonstrated being able to detect in real‐time the gamma‐rays emitted by annihilation of ¹⁸ F radiotracer. Its reliability is assessed by ¹⁸ F half‐life measurement with a maximum accuracy deviation within 8%. The detector also successes in its validation for the foreseen application, demonstrating able to monitor in real‐time the whole injection process and extravasation event.

Ultra-High Molecular Weight Polyethylene (UHMWPE), the standard base material in ski manufacturing, offers excellent gliding performance but exhibits limited mechanical and scratch resistance on hard and icy snow conditions. In this work, stainless steel is proposed as a mechanically robust alternative, and its inherently higher friction against snow is addressed through surface engineering. The snow friction behavior of 301H stainless steel surfaces decorated with fishbone-like microstructures combined with Laser-Induced Periodic Surface Structures (LIPSSs) was investigated using a custom-built snow tribometer. Several pattern designs, with different pitch distances and depths, were engraved using femtosecond laser pulse irradiation. We conducted morphological, physical, and chemical investigations through microscopy, static contact angle measurements, and X-ray Photoelectron Spectroscopy analyses. Results indicate that the gliding performance is not directly related to the modifications in surface chemistry and wetting behavior of the samples but is affected by the geometry and orientation with respect to the sliding direction of the specific micro- and nano-features. Overall, we achieved friction coefficient values comparable to those found in UHMWPE with a fast and economically sustainable single-step laser-texturing process. This approach allows the industrial up-scaling of the fishbone-texture design to real-size alpine ski prototypes.

The development of high performance, thin and flexible light and radiation sensors for real-time detection of ionizing radiation at affordable cost is of interest in many application areas, ranging from medical diagnostics and therapy to astrophysics, high energy physics and industrial testing, including civil radiation protection. The use of organic semiconductor technology could meet the requirements of large area, conformability and portability, light weight and low power operation. In the field of organic photodetectors, phototransistors (OPT) have gained significant attention due to their ability to combine high sensitivity, switching function, and intrinsic amplification without noise problems in a single device, thus allowing significant simplification of the external signal conditioning circuitry [1]. The operation of an OPT under light illumination is governed by the trapping of minority carriers, resulting in a reduction of the threshold voltage which determines an increase in the majority carrier density and, consequently, an increase of the photocurrent [2]. The increase of photocurrent in organic semiconductors has been attributed by several authors to an increase in the trapping of minority carriers induced by light exposure. In fact, the light-induced creation of deep traps for carriers has already been experimentally demonstrated in the analysis of several organic semiconductors used in different optoelectronic applications [3]. Moreover, TCAD simulations show that the photocurrent can be assumed linearly dependent upon the total amount of generated traps, at least for the range of radiation exposures used in this work. In this work, we present a dedicated kinetic model capable of correctly describing the photocurrent behavior in dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) based OPTs operating in subthreshold condition. The OPTs have been used as direct light detectors and in an indirect flexible proton detector that has been fabricated by coupling a 500 μm thick scintillating plastic film (a polysiloxane-based matrix carrying a primary dye and a wavelength shifter) directly on top of the OPT’s passivation layer. By analyzing the response of the OPTs in light and in the proton detectors we note that: 1 - the relaxation in dark of the photocurrent (fig. A) is well described by a stretched exponential with an exponent β almost constant (around 0.5) and a characteristic time τ_s that strongly depends on the exposure conditions (fig. B). 2 - dynamic photocurrent measurements under repeated exposures show a systematic drift due to the build-up of a persistent photocurrent component that decays with a characteristic times of the order of 10⁵ s, in addition to the swift component that has recovery times in the range of a few seconds (fig. C). To model these effects, we propose a set of rate equations similar to the one already presented by Street et al [3], suitably modified to reproduce the dynamics of the creation and recovery of two different types of defects with distributed recovery activation energies. The consideration of two different types of defects allows the reproduction of the swift and persistent photocurrent components, while the stretched exponential behavior of the photocurrent decay is reproduced by introducing a distribution in the recovery activation energies. The proposed new model is able to quantitatively reproduce the dynamic photoresponse for a wide range of exposure intensities under both photon and proton fluxes [4]. As can be seen in fig. C, the curves computed by the model with the fitted parameters superimpose well on the experimental ones, correctly reproducing the rise and fall dynamics of the exposure response and the progressive build-up of a persistent photocurrent. The model also provides some valuable physical insights to explain some features of the dynamic photoresponse. This work has been funded by the Italian National Institute of Nuclear Physics – INFN -5th commission, under the “FIRE” project (2019-2023). Lucas, T. Trigaud, C. Videlot-Ackermann, Organic transistors and phototransistors based on small molecules: Organic transistors and phototransistors, Polym. Int. 61 (2012) 374–389. https://doi.org/10.1002/pi.3213 Basiricò, L. et al. Direct X-ray photoconversion in flexible organic thin film devices operated below 1 V. Nat Commun 7, 13063 (2016). Street, R. A., Yang, Y., Thompson, B. C. & McCulloch, I. Capacitance Spectroscopy of Light Induced Trap States in Organic Solar Cells. J. Phys. Chem. C 120, 22169–22178 (2016). S. Calvi, L. Basiricò, S. M. Carturan, I. Fratelli, A. Valletta, A. Aloisio, S. De Rosa, F. Pino, M. Campajola, A. Ciavatti, L. Tortora, M. Rapisarda, S. Moretto, M. Verdi, S. Bertoldo, O. Cesarini, P. Di Meo, M. Chiari, F. Tommasino, E. Sarnelli, L. Mariucci, P. Branchini, A. Quaranta, B. Fraboni, “Flexible fully organic indirect detector for megaelectronvolts proton beams”, npj Flexible Electronics (2023) 7:5; https://doi.org/10.1038/s41528-022-00229-w. Figure 1

This study presents an automated methodology for evaluating micro-channels fabricated using a femtosecond laser on stainless steel substrates. We utilize 3D surface topography and metrological analyses to extract geometric features and detect fabrication defects. Standardized samples were analyzed using a light interferometer, and the resulting data were processed with Principal Component Analysis (PCA) and RANSAC algorithms to derive channel characteristics, such as depth, wall taper, and surface roughness. The proposed method identifies common defects, including bumps and V-defects, which can compromise the functionality of micro-channels. The effectiveness of the approach is validated by comparisons with commercial solutions. This automated procedure aims to enhance the reliability and precision of femtosecond laser micro-milling for industrial applications. The detected defects, combined with fabrication parameters, could be ingested in an AI-based process to optimize fabrication processes.