Study On The Solution Growth And Properties Of CsPbBr₃ Crystals For High Energy Radiation Detection

Compared with organic-inorganic hybrid perovskite materials,inorganic metal-halide perovskite materials exhibit excellent photo-electrical properties,and more importantly,higher chemical stability.As a family member of inorganic perovskite materials,CsPbBr₃ has high average atomic number（Z_A=48.4）,large band gap（～2.29 e V）,high resistivity(～10¹⁰Ω·cm)and outstanding charge transport properties.Therefore,CsPbBr₃ is a promising material for the fabrication of room-temperature radiation semiconductor detector.In this work,CsPbBr₃ single crystals were successfully grown by modified antisolvent vapor-assisted crystallization（AVC）method and inverse temperature crystallization（ITC）method,respectively.In AVC method,the phase diagram of the final products was identified by adjusting the mole ratio of Pb Br₂ and Cs Br（n）,which has four regions,Cs₄Pb Br₆ single phase region（n<0.25）,Cs₄Pb Br₆ and CsPbBr₃ two phases region（0.25<n<1）,CsPbBr₃ single phase region（1<n<1.5）,and CsPbBr₃and Pb Br₂·2[（CH₃）₂SO]two phases region（n>1.5）,respectively.By diluting the anti-solvent methanol（Me OH）with dimethyl sulfoxide（DMSO）,centimeter-sized CsPbBr₃ single crystals（42×5×3 mm³）were obtained.On the other hand,the water bath equipment was modified to grow CsPbBr₃ crystals by using ITC method.The as-grown crystals with the size of～10×9×3 mm³ were obtained,and the crystalline quality was relatively high compared with AVC method.The mixed solvents consist of cyclohexanol（Cy OH）and dimethylformamide（DMF）with the volume ratio of1:1.8 were adopted in ITC method,and the growth rate of the temperature was～1?C/day.Both optical and electrical properties of the CsPbBr₃ crystals grown by low-temperature solution methods were measured.The results showed that CsPbBr₃has the band gap of～2.29 e V,and the PL spectra indicated there were two peaks located at 530 nm and 560 nm.The fitting carriers decay time was 2.9 ns and 25.1 ns originated from surface combination and body combination,respectively.The Hall effect measurement showed that CsPbBr₃ was p-type semiconductor.CsPbBr₃exhibited high resistivity of 10⁹Ω·cm and the ON-OFF ratio of 10²illuminated using a LED light（420 nm,1 m W/cm²）.These results showed that CsPbBr₃ has excellent photoresponse properties,which are necessary for hard radiation detection.Subsequently,theαparticles and X-ray response were carried out.By fitting the pulsed waveforms,the electron and hole mobility was obtained,with the value of1368±52 cm² V^-1s^-1 and 2652±158 cm² V^-1s^-1,respectively,which were larger than that obtained from melt-grown CsPbBr₃.The detection sensitivity under different X-ray photons was investigated.By modifying the configuration of the device into Al/CsPbBr₃/Au,the ion transportation was significantly impeded,and a maximum sensitivity of 1256μCGy^-1cm^-2 was achieved,which was 60 times higher than the commercialα-Se detectors.Finally,the growth of doped CsPbBr_3-nX_n crystals was investigated.The relationship between actual doping ratio and theoretical doping ratio was examined,which was described by the doping coefficient k.The values of k were 0.97 and 0.046for Cl atom and I atom doping,respectively.