The development of detectors for protons and X-rays is a long-lasting research topic not only for fundamental applications, but more recently, in the medical field for hadron- and radio-therapy of cancer. In this application, ion beams are used for the controlled treatment of cancer by focusing them onto small volumes, to avoid the spreading of the radiation to healthy tissues. For this reason, there is an increasing demand of systems optimized for the accurate in-situ, real-time recording and mapping of the dose delivered during a treatment plan. Metal halide perovskites are rapidly emerging as active materials in low­c-ost high performing ionizing radiation detectors thanks to strong absorption of ionizing radiation, high charge carrier mobilities, long exciton diffusion, long charge carrier lifetime, and excellent optical properties. [1] Further, they combine the high performance of traditional inorganic semiconductors with the low­cost, large area scalable, deposition methods (i.e., printing technologies) typical of organic semiconductors. However, the direct proton beam detection or dose-monitoring by perovskite based devices has scarcely explored yet.

In this work, we propose novel flexible proton detectors based on 2D and mixed 3D and 2D perovskites films deposited from solution [2]. Mixed 3D-2D perovskites are formed by mixing 3D (based on methylammonium (MA) cations) and 2D (based on larger organic ammonium (OA) cations) structure perovskites. Their employment has been reported as an effective strategy to retain the exceptional transport properties of 3D perovskites and the high stability induced by the layered structure of 2D perovskites. By adding the 3D phase (MAPbBr₃) we here aim to enhance the radiation absorption of protons by the perovskite film, thanks to the higher density of MAPbBr₃ and to the higher thickness of the active layer for mixed compounds.On the other side, the high resistivity of the pure 2D perovskite active layer lowers the dark current of about 2 orders of magnitude with respect to the 2D/3D mixed perovskite improving the Signal to Noise ratio of the detector

The here proposed devices demonstrate an accurate monitoring of proton dose with instant feedback and low limit of detection, and provide a stable response even after hard and long-lasting proton irradiation. The performance of this novel tool is here compared with the one offered by standard commercial large-area technology, namely radiochromic sheets. We demonstrate the great potential of this class of devices by successfully mapping in real-time a 5 MeV proton beam at fluxes between 10⁸ H⁺ s^-1 cm^-2 and 10¹⁰ H⁺ s^-1 cm^-2, confirming the capability to operate in a radiation harsh environment without output signal saturation issues. The versatility and scalability of here proposed detecting system are demonstrated by the development of a multipixel array able to map in real-time a X-ray beam spot.

The presented results provide an effective solution to the challenge of identifying novel functional materials and portable devices for real-time accurate monitoring of proton dose, addressing the quest for radiation hardness, low-cost scalability over large areas and mechanical flexibility, still unsolved for a range of application which span from personal dosimetry to large area and lightweight detectors for large accelerators facilities and space missions.