X-ray scintillation in lead-free double perovskite crystals

Metal halide perovskites have shown great performance for various applications,including solar cells,light emitting diodes,and radiation detectors,but they still suffer from the toxicity of lead and instability.Here we report the use of lanthanide series as trivalent metals to obtain low toxicity and highly stable double perovskites(Cs_2NaLnCl_6,Ln=Tb or Eu)with high scintillation light yield.The crystals exhibit typical f-f transitions of lanthanide cations,while Cs_2NaTbCl_6exhibits strong green photoluminescence,and Cs_2NaEuCl_6exhibits red photoluminescence.Under X-ray radiations,the light yield of Cs_2NaTbCl_6reaches46600 photons MeV^(-1),much higher than that of the commercially used(Lu,Y)_2SiO_5:Ce^(3+)crystals(LYSO,28500 photons MeV^(-1)),and previously reported lead-based perovskites(14000 photons MeV^(-1)).As a new member of lead-free perovskites,lanthanide-based double perovskites open up a new route toward radiation detections and potential medical imaging.

Organic–inorganic hybrid perovskite scintillators for mixed field radiation detection

Sensitive and fast detection of neutrons and gamma rays is vital for homeland security,high-energy physics,and proton therapy.Fast-neutron detectors rely on light organic scintillators,andγ-ray detectors use heavy inorganic scintillators and semiconductors.Efficient mixed-field detection using a single material is highly challenging due to their contradictory requirements.Here we report hybrid perovskites(C_(8)H_(12)N)_(2)Pb(Br_(0.95)Cl_(0.05))_(4)that combine light organic cations and heavy inorganic skeletons at a molecular level to achieve unprecedented performance for mixed-field radiation detection.High neutron absorption due to a high density of hydrogen,strong radiative recombination within the highly confined[PbX_(6)]^(4-)layer,and sub-nanometer distance between absorption sites and radiative centers,enable a light yield of 41000 photons/MeV,detection pulse width of 2.97 ns and extraordinary linearity response toward both fast neutrons andγ-rays,outperforming commonly used fast-neutron scintillators.Neutron energy spectrum,time-of-flight based fast-neutron/γ-ray discrimination and neutron yield monitoring were all successfully achieved using(C_(8)H_(12)N)_(2)Pb(Br_(0.95)Cl_(0.05))_(4)detectors.We further demonstrate the monitoring of reaction kinetics and total power of a nuclear fusion reaction.We envision that molecular hybridized scintillators open a new avenue for mixed-field radiation detection and imaging.

Vertical matrix perovskite X-ray detector for effective multi-energy discrimination

Multi-energy X-ray detection is sought after for a wide range of applications including medical imaging,security checking and industrial flaw inspection.Perovskite X-ray detectors are superior in terms of high sensitivity and low detection limit,which lays a foundation for multi-energy discrimination.However,the extended capability of the perovskite detector for multi-energy X-ray detection is challenging and has never been reported.Herein we report the design of vertical matrix perovskite X-ray detectors for multi-energy detection,based on the attenuation behavior of X-ray within the detector and machine learning algorithm.This platform is independent of the complex X-ray source components that constrain the energy discrimination capability.We show that the incident X-ray spectra could be accurately reconstructed from the conversion matrix and measured photocurrent response.Moreover,the detector could produce a set of images containing the density-graded information under single exposure,and locate the concealed position for all low-,medium-and high-density substances.Our findings suggest a new generation of X-ray detectors with features of multi-energy discrimination,density differentiation,and contrast-enhanced imaging.

Dark current modeling of thick perovskite X‑ray detectors

Metal halide perovskites(MHPs)have demonstrated excellent performances in detection of X-rays and gamma-rays.Most studies focus on improving the sensitivity of single-pixel MHP detectors.However,little work pays attention to the dark current,which is crucial for the back-end circuit integration.Herein,the requirement of dark current is quantitatively evaluated as low as 10^(−9)A/cm^(2)for X-ray imagers integrated on pixel circuits.Moreover,through the semiconductor device analysis and simulation,we reveal that the main current compositions of thick perovskite X-ray detectors are the thermionic-emission current(J_(T))and the generation-recombination current(J_(g-r)).The typical observed failures of p-n junctions in thick detectors are caused by the high generation-recombination current due to the band mismatch and interface defects.This work provides a deep insight into the design of high sensitivity and low dark current perovskite X-ray detectors.

Solution-Processed Hybrid Europium (Ⅱ) lodide Scintillator for Sensitive X-Ray Detection

Lead halide perovskite nanocrystals have recently demonstrated great potential as x-ray scintillators,yet they stll suffer toxicity issues,inferior light yield(LY)caused by severe self-absorption.Nontoxic bivalent europium ions(Eu^(2+))with intrinsically efficient and self-absorption-free d-f transition are a prospective replacement for the toxic Pb^(2+).Here,we demonstrated solution-processed organic-inorganic hybrid halide BA_(10)Eul_(12)(BA denotes C_(4)H_(9)NH_(4)^(+))single crystals for the first time.