Synthesis And Luminescent Properties Of All-inorganic Perovskite Microstructures

In order to display the color of an object as realistically as possible,a backlighting display must use a material capable of emitting ultra-pure light to obtain the widest possible color gamut.The human eye is extremely sensitive to the green color,so the search for high-efficiency pure-green luminescent materials has always been the goal pursued by researchers.In addition,the backlighting display displays the shape and color of the object through the combination of pixel dot matrix,so light emitting arrays are important to realize this function.All-inorganic perovskites are expected to be candidate materials in backlighting display field due to their relatively excellent environmental stability,precise control of emission wavelength,high defect tolerance,significant exciton emission,and high photoluminescence quantum yield（PLQY）.For pure-green light emission,although the spontaneous assembly method can achieve pure-green light emission,the self-assembled supercrystals may decompose in the diluted solution,which will cause the shift and broadening of the emission peak.For light emitting arrays,the currently reported thermal imprinting,etching-film,two-step method and polydimethylsiloxane（PDMS）-template-confined method synthesized perovskite arrays have poor crystal-quality,so it is necessary to explore a new method to synthesize high-quality all-inorganic perovskite arrays.In addition,perovskite crystals exhibit double-peak emission due to the Rashba effect,which is unfavorable for monochromatic luminescence.Therefore,it is necessary to explore the mechanism of Rashba effect and control it.In order to solve the above problems,We realize controllable synthesis of Cs Pb Br₃ microstructures（microplates,pyramid samples and microspheres）and Cs Pb X₃ submicron plate arrays by vapor-phase method,which achieves stable high-efficiency pure-green light emission,high-quality perovskite arrays and phase-dependent Rashba effect.The research content specifically includes the following three parts:（1）By controlling the growth time and cooling rate,we used chemical vapor deposition（CVD）to synthesize Cs Pb Br₃ microplates,pyramid samples and microspheres.X-ray diffraction（XRD）pattern results showed that the microplates were cubic crystal phase,while the pyramid samples and microspheres were monoclinic crystal phase.This different crystal phase was due to the difference in cooling rate.The reflectance spectra showed that the three kinds of samples had the same optical band gap（2.353 e V）,but the microspheres had stronger photoluminescence（PL）intensity and higher PLQY.Temperature-dependent PL spectra showed that it was due to the lower longitudinal optical（LO）phonon energy of the microspheres.In addition,we can continuously change the diameter of the microspheres（2-50μm）by placing the silicon substrate at different deposition positions,and then achieved the tunable peak position of the microspheres to cover the pure-green wavelength range（525-535 nm）.（2）The all-inorganic perovskite submicron plate arrays were successfully synthesized using seed-assisted spaced-confined vapor-phase growth method.Through the epitaxial growth of seeds array,we had successfully grown all-inorganic perovskite submicron plates.The space-confined effect played a crucial role in the growth of submicron scale.These submicron plates emitted ultra-low threshold（0.22μJ/cm²）whispering-gallery-mode（WGM）laser,and the submicron-scale lateral size led to the single longitudinal mode WGM output.By changing the composition and proportion of halogen atoms in the all-inorganic perovskites,we successfully synthesized Cs Pb I₃ and Cs Pb Br_xI_3-x submicron plates,and realized an ultra-low threshold single-mode laser that can cover the green to red wavelength range.（3）The phase-dependent Rashba effect was successfully realized in the all-inorganic perovskite microstructures.The circularly polarized galvanic effect（CPGE）and temperature-dependent PL spectra proved that the Cs Pb Br₃ microplates and pyramids have the Rashba effect.By comparing the energy difference of the low-energy luminescent peak and the high-energy luminescent peak and calculating the Rashba parameters of different crystal phase samples,we proved that the crystal phase is a factor that affects the strength of the Rashba effect,and this influence mechanism is likely to be related to exciton-acoustic phonon coupling strength.