Synthesis Of Lead-free Metal Halide Single Crystals And Their Application For X-Ray Detection

X-ray detectors are now widely used in various fields,including industrial flaw detection,medical imaging,security inspection,scientific research characterization,etc.X-ray detectors can be divided into X-ray direct detectors and X-ray indirect detectors（scintillator detectors）according to the signal conversion process.The X-ray direct detectors convert X-ray photons into electrical signals.The scintillator detector first converts X-ray photons into visible photons,then visible photons are converted into electrical signal.Due to the strong penetration of X-rays,the detector materials need a high density and high atomic number to obtain a high attenuation factor against X-rays,as well as a sufficient thickness to absorb X-rays.Lead-based halide perovskite materials have high X-ray attenuation coefficients,and have been studied for X-ray detection because of their excellent photoelectric properties.However,lead-based materials are not environmentally friendly,so lead-free and non-toxic perovskite is also an important research object.This thesis is dedicated to optimizing the growth of lead-free metal halide single crystals and studying their X-ray detection performance.The research focuses on two materials,Cs₂AgBiBr₆ and Rb₂Cu Br₃.The main work is as follows:1)Single crystals were grown using a controlled cooling method.By studying the solubility and super-solubility of the materials in the acid solution,the single crystal growth process was optimized based on the solubility and super-solubility curves.Photoconductive devices using Cs₂AgBiBr₆ single crystals were fabricated with a"gold electrode/Cs₂AgBiBr₆ single crystal/gold electrode"structure.The photoelectric performance and X-ray detection performance of the Cs₂AgBiBr₆ single crystal were studied.Synthesized by the optimized fixed growth process,the Cs₂AgBiBr₆ single crystals exhibits higher X-ray detection performance.It has a higher sensitivity of 2.0×10³μC?Gy^-1_air?cm^–2and lower detection limit of 45.7 n Gy_air s^-1,which is beneficial to detection at a low dose rate.The optimized synthesis method also ensures the devices repeatability.The resistivity of optimized devices has a narrower distribution range of 6.10×10⁹～3.31×10¹⁰Ωcm,while the un-optimized devices have a range of 6.04×10⁷～5.61×10⁹Ωcm.2)Based on the Cs₂AgBiBr₆ single crystal growth process,high-quality Rb₂Cu Br₃single crystals were synthesized and optimized,of which the photoluminescence was characterized.Through the standard-sample-comparison light yield testing system,its scintillation properties were characterized.Rb₂Cu Br₃has a high photoluminescence quantum yield of98.6%and light yield of 21600 photons Me V^-1,which exhibits its potential for scintillator application.