Zero-dimensional Organic Manganese Bromide Wafers For High Performance Direct X-ray Detector

High-performance direct X-ray detectors have a wide range of applications,including medical examinations,security inspections,and computed tomography.Metal halides are the next generation of X-ray detection materials due to their high X-ray attenuation coefficients,large mobility-lifetime（μτ）and defect tolerance,and low-cost preparation.However,limited by severe ion migration and large dark current/noise,the search for novel X-ray detection materials and device preparation processes is necessary.Notably,low-dimensional metal halides can significantly affect the ion migration properties.In addition,easy-to-process low-cost large-area preparation processes and integration processes need more research.In this paper,the above issues are explored with the aim of developing high-performance direct X-ray detector of organic manganese bromide A₂Mn Br₄（A is the organic cation）with material properties compatible with the preparation process.The research of this thesis is as follows:（1）Zero-dimensional（0D）benzyltrimethylammonium manganese bromide（BTA₂Mn Br₄）materials have been synthesized in order to obtain crystal structures with noise and ion migration suppression.Due to the high exciton binding energy（115.6me V）and large bandgap（3.20 e V）,BTA₂Mn Br₄ has great potential in the field of X-ray detection.Meanwhile,in search of a low-cost preparation process,BTA₂Mn Br₄wafer is prepared using the isostatic pressure method,and the sensitivity of this detector is as high as 3495μC Gy_air^-1 cm^-2 with a detection limit as low as 105 n Gy_airs^-1.This indicates that the use of low-dimensional materials for high-performance detectors is feasible.（2）The melt processing method is reported for the preparation of highly dense BTA₂Mn Br₄ wafers.This process can successfully improve the problems such as large wafer apertures and poor stability,making the detector have higher charge collection efficiency.More importantly,the BTA₂MnBr₄ wafer is integrated into the substrate of the pixelated electrodes by melt processing to meet the practical detection imaging requirements,and the stability performance and imaging applicability of the devices are investigated.It is hoped that this work will contribute to the research development of large area X-ray imaging systems.（3）The 0D organic manganese bromide A₂Mn Br₄ is synthesized by using A-site cation engineering.The distance between adjacent Mn atoms was changed by using different sizes and chain lengths of organic cations.Therefore,the long-chain Trimethylphenylammonium manganese bromide（PTA₂Mn Br₄）has stronger luminescence,smaller defect density and less non-radiative complex than the short-chain Dimethylammonium manganese bromide（DMA₂Mn Br₄）.Further,the detection performance of the DMA₂Mn Br₄ and PTA₂Mn Br₄ wafers-based devices was measured.the PTA₂Mn Br₄ based device has higher sensitivity and lower detection limit than the DMA₂Mn Br₄.This suggests that A-site cation engineering is an effective strategy for developing high-performance low-dimensional structures of organic manganese bromide.