On the Role of Cs4PbBr6 Phase in the Luminescence Performance of Bright CsPbBr3 Nanocrystals

High-quality and stable perovskite nanocrystals with enhanced properties via photo-brightening

Colloidal inorganic perovskite CsPbX3 nanocrystals (NCs) with extraordinary properties have emerged as key materials for light management in next-generation optoelectronic devices. Cyan-emitting perovskites show strong potential for high-quality lighting applications. In terms of post-treatment, light irradiation can cause considerable changes in optical features, leading to either photo-brightening or photo-darkening effects. Here, we report a facile strategy and detailed protocols for the synthesis of high-quality, stable Cs-Pb-Br NCs that emit green-blue light by systematically varying the PbBr2 ratios. The proposed strategy enables the reproducible preparation of Cs-Pb-Br NCs with narrow size distributions. In addition, photo-brightening in high-quality and stable Cs-Pb-Br perovskite NCs enhanced the photoluminescence (PL) properties. Under laser irradiation, the cyan-emitting Cs-Pb-Br NCs with a Cs:Pb molar ratio of 1:10.4 exhibited a ∼40 % increase in PL intensity, attributed to the repair of Br vacancies by O2 adsorption.

Size-Dependent Multiexciton Dynamics Governs Scintillation From Perovskite Quantum Dots

The recent emergence of quantum-confined nanomaterials in the field of radiation detection, in particular lead halide perovskite nanocrystals, offers scalability and performance advantages over conventional materials. This development raises fundamental questions about the mechanism of scintillation itself at the nanoscale and the role of particle size, arguably the most defining parameter of quantum dots. Understanding this is crucial for the design and optimization of future nanotechnology scintillators. In this work, these open questions are addressed by theoretically and experimentally studying the size-dependent scintillation of CsPbBr3 nanocrystals using a combination of Monte Carlo simulations, spectroscopic, and radiometric techniques. The results show that the simultaneous effects of size-dependent energy deposition, (multi-)exciton population, and light emission under ionizing excitation, typical of confined particles, combine to maximize the scintillation efficiency and time performance of larger nanocrystals due to greater stopping power and reduced Auger decay. The agreement between theory and experiment produces a fully validated descriptive model that predicts the scintillation yield and kinetics of nanocrystals without free parameters, providing fundamental guidance for the rational design of nanoscale scintillators.

Ambient Air-Synthesized CsPbBr3 Nanocrystals Coupled with TiO2 Film as an Efficient Hybrid Photoanode for Photoelectrochemical Methanol-to-Formaldehyde Conversion

Due to its exceptional optoelectronic properties in the visible spectrum, cesium lead bromide (CsPbBr3) perovskite has attracted considerable attention in solar-driven organic transformations via photoelectrochemical (PEC) cells. However, the performance of the devices is adversely affected by electron-hole recombination occurring between a transparent conductive substrate, such as fluorine-doped tin dioxide (FTO), and a perovskite layer. Herein, to mitigate this issue, a compact layer of titanium dioxide (TiO2) was employed as both an electron transport layer and a hole blocking layer to diminish charge recombination while facilitating electron transfer in such perovskite material. At the oxidation peak potential of 0.70 V vs Ag/AgNO3, a hybrid photoanode of CsPbBr3/TiO2/FTO exhibited a significant increase in photocurrent density, from 15 to 41 μA/cm2, compared to a configuration without a TiO2 layer. Furthermore, the introduction of methanol as a hole scavenger in the PEC system using the hybrid photoanode facilitated the separation of electron-hole pairs, which led to an enhanced photocurrent density of 60 μA/cm2 and promoted the production of formaldehyde. High-performance liquid chromatography (HPLC) confirmed the generation of formaldehyde at a concentration of 26.69 μM with a Faradaic efficiency of 92% under an applied potential of 0.50 V vs Ag/AgNO3 for 60 min of PEC reaction. In addition to the enhanced PEC performance achieved from this hybrid photoanode, CsPbBr3 nanocrystals (NCs) in this work were synthesized by the modified one-pot method under ambient air, where highly uniform and high-purity NCs were obtained. This work signifies the groundbreaking exploration of CsPbBr3 NCs with TiO2 as a photoelectrode material in the organic-based PEC cells, which efficiently improved the interfacial charge transfer within the photoanode for the conversion of methanol to formaldehyde, marking a significant advancement in the field.

Metal halide perovskite polymer composites for indirect X-ray detection

Metal halide perovskites (MHPs) have emerged as a promising class of materials for radiation detection due to their high atomic numbers and thus high radiation absorption, tunable and efficient luminescent properties and simple solution processability. Traditional MHP scintillators, however, suffer from environmental degradation, spurring interest in perovskite-polymer composites. This paper reviews recent developments in these composites tailored for scintillator applications. It discusses various synthesis methods, including solution-based and mechanochemical techniques, that enable the formation of composites with enhanced performance metrics such as light yield, detection limit, and environmental stability. The review also covers the remaining challenges and opportunities in fabrication techniques and performance metric evaluations of this class of materials. By offering a comprehensive overview of current research and future perspectives, this paper underscores the potential of perovskite-polymer composites to revolutionize the field of radiation detection.

Perovskite Scintillators for Improved X-ray Detection and Imaging

Halide perovskites (HPs) recently have emerged as one class of competitive scintillators for X-ray detection and imaging owing to its high quantum efficiency, short decay time, superior X-ray absorption capacity, low cost, and ease of crystal growth. The tunable structure and versatile chemical compositions of halide perovskites provide distinguishable advantages over traditional inorganic scintillators for optimizing scintillation performance. Since the first observation of the scintillation phenomenon in HPs, substantial efforts have been devoted to expanding the inventory of HP scintillators and regulating material properties. Understanding the relationship between the structure and scintillation properties of HP scintillators is essential for developing materials with improved X-ray detection and imaging capacities. This review summarizes strategies for improving the light yield of HP scintillators and provides a roadmap for improving the X-ray imaging performance. Additionally, methods for controlling the light propagation direction in HP scintillators are highlighted for improving X-ray imaging resolution. Finally, we highlight the current challenge in HP scintillators and provide a perspective on the future development of this emerging scintillator.

Scintillation Response Enhancement in Nanocrystalline Lead Halide Perovskite Thin Films on Scintillating Wafers

Lead halide perovskite nanocrystals of the formula CsPbBr₃ have recently been identified as potential time taggers in scintillating heterostructures for time-of-flight positron emission tomography (TOF-PET) imaging thanks to their ultrafast decay kinetics. This study investigates the potential of this material experimentally. We fabricated CsPbBr₃ thin films on scintillating GGAG:Ce (Gd_2.985Ce_0.015Ga_2.7Al_2.3O₁₂) wafer as a model structure for the future sampling detector geometry. We focused this study on the radioluminescence (RL) response of this composite material. We compare the results of two spin-coating methods, namely the static and the dynamic process, for the thin film preparation. We demonstrated enhanced RL intensity of both CsPbBr₃ and GGAG:Ce scintillating constituents of a composite material. This synergic effect arises in both the RL spectra and decays, including decays in the short time window (50 ns). Consequently, this study confirms the applicability of CsPbBr₃ nanocrystals as efficient time taggers for ultrafast timing applications, such as TOF-PET.