Preparation Of High-Quality Two-Dimensional Perovskite（PEA）₂FA_n-1Pb_nBr_3n+1 Films And Study Of Low-threshold Amplified Spontaneous Emission

As a new class of semiconductor materials that can be prepared by solution method,perovskites offer the possibility to realize low-cost lasers.Metal halide perovskites have the characteristics of high fluorescence quantum efficiency,high light absorption coefficient,and long carrier diffusion length,so they attract much attention in the field of optoelectronic devices.Two-dimensional perovskites not only have higher environmental stability than the three-dimensional perovskites,but also have a series of characteristics of the perovskite material itself,which have received extensive attention in the field of optoelectronic devices.Due to the quantum confinement effect,two-dimensional perovskites have high exciton binding energy and strong luminescence ability.However,at high current densities,the aggregated ligands generate strong internal Joule heating and Auger recombination,resulting in short working time of light-emitting diode devices,and electrically pumped laser fails to achieve.Quasi-two-dimensional perovskites have a special self-assembled multiple quantum well structure,which affects the internal energy flow and radiation recombination mechanism,so the luminescence performance can be further improved by adjusting the distribution of quantum wells.Based on this,we fully study the preparation process of quasi-2D perovskite thin films,including adjusting the ratio of raw materials,successfully reducing the spontaneous emission threshold of quasi-2D perovskite,and designing the corresponding distributed feedback laser.The main research contents of this paper include the following two aspects:1.The quasi-two-dimensional perovskite film was prepared by a one-step spin coating method.By adjusting the preparation process,the precursor concentration of the quasi-two-dimensional perovskite and the dropping time of the anti-solvent toluene got optimized,and films with a roughness of about 3 nm were obtained.After that,the ratio of raw materials was adjusted,and some quantum wells with n values of 3 to 5 were added to the quasi-two-dimensional perovskite film at a ratio of PEABr:FABr:Pb Br₂ of 2:7.96:7.96.Benefit from the formation of better gradient distribution of quantum wells with different n values,the characteristic of the energy funnel structure is fully utilized,the loss caused by self-defects when amplifying spontaneous emission is reduced,and a large spontaneous emission threshold of about 16μJ/cm² is obtained,It is nearly twice lower than the 31μJ/cm² reported in the literature for this material.In addition,through the photoluminescence time-resolved test,it was found that the film was dominated by higher-efficiency exciton radiation recombination,which further improved the luminescence performance.2.A distributed feedback resonator corresponding to the prepared quasi-2D perovskite film is designed.According to the characteristics of the Bragg grating in the distributed feedback resonator,the parameters of the Bragg grating are preliminarily designed.Through numerical simulation,the theoretical feasibility of these parameters is confirmed.According to the actual preparation conditions,the duty cycle and the etching depth were further optimized.By appropriately reducing the duty cycle of the gain part,at the gain medium duty cycle of 53%,a grating structure with a grating width of 134 nm and a height of 80 nm is obtained,making it meet the level of the actual fabrication process.The preparation of quasi-two-dimensional perovskite distributed feedback lasers provides a theoretical basis.