The study evaluated the use of CsPbBr3 crystals in hybrid detectors with integrated circuit developed at CERN
Researchers from the Brazilian Center for Research in Energy and Materials (CNPEM) and the State University of Campinas (Unicamp) investigated the potential of lead-based perovskites to develop more efficient high-energy X-ray detectors.
The study was published in the Scientific Reports journal, which is part of the Nature portfolio, and addressed a crucial challenge for synchrotron light sources, such as Sirius: ensuring the efficient detection of high-energy photons during advanced imaging experiments, including techniques such as X-ray micro- and nanotomography.
The analyzed material, a CsPbBr3 perovskite crystal, demonstrated high electronic compatibility with CERN’s modern Timepix4 chip, and showed promise for the creation of hybrid detectors capable of recording more energetic X-rays with greater efficiency.
The challenge of detecting high-energy X-rays
Imaging experiments with high-energy photons are essential for investigating the structure and behavior of materials at microscopic or nanoscopic scales. At a synchrotron light source like Sirius, these techniques allow us to observe sample details non-destructively, which is very important for areas such as soil science, development of new drugs, studies of neglected diseases, development of catalysts or advanced materials.
However, detecting photons with energy above 90 keV is not a simple task. Properties such as density and the so-called “absorption cross–section“ of semiconductor materials used in detector manufacturing have a direct impact on absorption efficiency in higher energy ranges. This limits the quality of the images obtained and, consequently, the analyses that researchers can perform based on the experiments.
This is where lead-based perovskites come into play. The name “perovskite” is used to refer to two things: a calcium and titanium mineral represented by the chemical formula CaTiO3 that occurs in metamorphic rocks, and a group of compounds that have a crystalline structure similar to this mineral. In the case of the study in question, the analyzed lead-based perovskite is represented by the formula CsPbBr3 and has very interesting properties for this application.
CsPbBr3 perovskite crystal (Credits: Outreach/CNPEM)
As Raul Campanelli, CNPEM researcher and one of the authors of the article, explains: “The absorption cross–section is a measure that determines the probability of interaction between radiation and matter. And the perovskites’ absorption cross-section for X-ray photons is quite large. This means that there is a high probability of detecting a photon arriving at this material, unlike silicon, for example, which has a low absorption cross-section and density, making it virtually transparent at high energies.”
What are hybrid pixel detectors?
The type of detector this research focused on is known as a “hybrid pixel detector”. In it, a semiconductor material sensor is connected to an integrated circuit, which is responsible for processing the electrical signal generated by the interaction of X-rays with the material.
“The general operation of a detector of this category consists of a set of phenomena. The semiconductor material present in these detectors has the function of absorbing the X-ray photons incident on its surface and transforming them into a packet of electrical charges. These electric charges are then accelerated by an electric field. And the transport of these charges along this semiconductor material generates signals in the form of current pulses in pixelated circuits on this surface”, highlights Raul.
Unlike so-called “indirect detectors”, which transform X-rays into visible light with the help of a scintillating material before generating electrical charges in the semiconductor, hybrid pixel detectors do the direct conversion: X-ray photons are absorbed by the sensor and generate electrical charges proportional to the energy of these photons. These charges are subsequently collected by small electrodes and processed by integrated microelectronic circuits.
Creating and evaluating perovskite crystals
To evaluate the performance of this material, CNPEM and UNICAMP researchers first had to produce high-quality crystals. This is because the presence of defects in the crystal structure can significantly reduce the mobility of electrical charges, compromising the detector’s efficiency.
Time-lapse recording of perovskite crystal growth at LNLS (Image adapted from Campanelli et al., Scientific Reports, 2025, https://doi.org/10.1038/s41598-024-74384-7)
The team used a crystal growth method already described in the literature, managing to generate single orange crystals with well-defined edges. The structural quality was confirmed by techniques such as X-ray diffraction and Laue diffraction. These experiments indicated the monocrystalline nature of the grown materials, avoiding defects that could impair charge propagation.
Set of CsPbBr3 perovskite crystals (Credits: Outreach/CNPEM)
To understand how these crystals behave in their intended application, researchers fabricated devices with different types of electrical contact and measured the mobility of charges generated by the interaction with X-ray photons. The collected data demonstrated that, despite the relatively simple manufacturing method, the observed characteristics are consistent with high-quality crystals.
Simulating detection
The next step of the research was to simulate how a detector made with CsPbBr3 responds to interaction with X-ray photons of different energies. Using the result obtained in the previous measurements, the team modeled the displacement of electrical charges inside the crystal and the current pulse signals generated in each pixel.
These simulations showed that, for the signal to be properly collected, it is necessary to apply more intense electric fields, in the order of 1 kV/mm, something already demonstrated for other applications with this and other high atomic number materials.
Signal simulation on CsPbBr3 sensor (1 mm, 44 μm electrode). (a) Current induced by photons of different energies; detail: charge trajectories. (b) Time to collect 90% charge vs. energy (800–1200 V). (c) Time vs. voltage for 90 keV photons (Image adapted from Campanelli et al., Scientific Reports, 2025, https://doi.org/10.1038/s41598-024-74384-7)
The results obtained through this method were used in conjunction with an electronic simulator that reproduces the behavior of Timepix4, the latest version of the electronic circuit developed at CERN for applications like this.
Impact and perspectives
The results indicate that CsPbBr3 is a viable candidate for use in hybrid pixel detectors aimed at high-energy X-ray detection. In addition to presenting high absorption efficiency and good load mobility, the material can be produced by relatively simple and low-cost methods, which facilitates its large-scale adoption.
“The next step in this process is hybridization, that is, joining the photosensitive semiconductor material with the pixelated electronic integrated circuit. And then, perform the entire process of metallization and soldering so that we can have control over the integrated circuit and thus collect data. This is all part of the prototype manufacturing process of a hybrid detector with perovskite”, highlights Raul Campanelli.
In the context of a synchrotron like Sirius, this technology can expand the capabilities of experiments that require higher-energy beams, such as tomography of large or dense samples, and techniques that benefit from greater radiation penetration.
Furthermore, the impact extends to areas such as medicine, where more sensitive and accurate detectors can improve imaging tests and treatments that use radiation, and for industry, in quality and safety inspection processes.
About CNPEM
The Brazilian Center for Research in Energy and Materials (CNPEM) is a state-of-the-art, multi-user and multidisciplinary scientific environment with activities on different fronts within the Brazilian National System for Science, Technology and Innovation. A social organization overseen by the Ministry of Science, Technology and Innovation (MCTI), CNPEM is driven by research that impacts the areas of health, energy, renewable materials, and sustainability and is responsible for Sirius, the country’s largest scientific research infrastructure. CNPEM is currently constructing Project Orion, a laboratory complex for advanced pathogen research. Highly specialized science and engineering teams, sophisticated infrastructure open to the scientific community, strategic lines of investigation, innovative projects involving the productive sector, and training for researchers and students are the pillars of this institution that is unique in Brazil and able to serve as a bridge between knowledge and innovation. Research and development activities at CNPEM are conducted by its National Laboratories in the areas of Synchrotron Light (LNLS), Biosciences (LNBio), Nanotechnology (LNNano), and Biorenewables (LNBR), as well as the Ilum School of Science, which offers a bachelor’s degree program in science and technology with support from the Ministry of Education (MEC).
