Research On Stability And Performance Of FAPbI₃ Perovskite As Laser Gain Medium

As an emerging optoelectronic material,perovskite material has excellent physical properties,it can not only be used as the light-absorbing layer of solar cells,but also is a very attractive material for laser applications.Perovskite materials have made great progress in both light-emitting diodes and optically pumped laser devices,which is expected to achieve the ultimate goal of electrically pumped perovskite laser devices.Exploring low-threshold and high-stability perovskites is very important for electrically pumped laser devices.In this paper,the threshold and stability of the perovskite are optimized through additive engineering and mixed cation strategies.The details are as follows:（1）Optimized the preparation process of FAPbI₃ perovskite film.Firstly,the influence of the one-step spin-coating deposition method and the two-step spin-coating deposition method on the threshold of FAPbI3 in the spin-coating method is compared.The results show that the one-step spin-coating deposition method is more suitable for preparing the perovskite film.Because the thresholds of the films prepared by the two methods are similar,the thresholds of the films prepared by the one-step method have higher repeatability.After comparing the effect of anti-solvent on FAPbI₃ film in one-step spin-coating deposition method,it is found that chlorobenzene can make the film surface flatter and have higher crystallinity compared with other anti-solvents.We also compared the stability and threshold of different A-site cationic perovskite films.The results show that CsPbI₃ can not form an effective perovskite film using a simple one-step spin-coating deposition method.The photo-thermal stability of FAPbI₃ is obvious compared with that of MAPbI₃.The threshold of FAPbI₃perovskite is relatively low,41.7μJ/cm².However,FAPbI₃ is prone to produce a non-optically activeβphase during preparation.This provides a goal for our follow-up work.（2）In order to make the phase transition of FAPbI3 complete,we used MAC1 as an additive to successfully induce FAPbI₃ to completely transform into the optically active phase.MAC1decomposes during the formation of FAPbI₃,where MA participates in the formation of perovskite,and the formation of FACl with Cl ions and FA escapes the perovskite under high temperature annealing conditions.The addition of MAC1 will significantly increase the crystal grains and increase the crystallinity.However,as the content of MACl exceeds 30%,voids and even cracks appear on the surface of the perovskite,and the surface roughness increases.During the threshold test,the 30%concentration of MACl-doped perovskite obtained the lowest threshold of 33.2μJ/cm²,which was only 79.6%of the MACl-undoped perovskite.However,in the subsequent light stability test,the stability of different concentrations of MAC1 did not differ greatly.The thermal stability test shows that the decomposition of MAPbI₃ involved in film formation at high temperatures leads to the destruction of the perovskite,and the threshold is increased.（3）Through the mixed cation strategy,that is,the A site is mainly FA,and a small amount of MA and Cs ions are mixed to prepare a perovskite film with high stability and low threshold.First,calculate according to the tolerance factor formula,the value of x in Cs_x(MA_0.17FA_0.83)_（1-x）PbI₃should be below 0.3.When x exceeds 0.3,a large area of voids appears on the surface of the perovskite film.There is also no perovskite crystal structure formed.In the threshold test,when x is 0.1-0.3,the threshold value does not change significantly,but the threshold value relative to FAPbI3 drops significantly.Taking Cs0.2 as an example,the threshold value is only 31.5μJ/cm².The subsequent light stability experiment results show that the stability of the tri-cation perovskite is much better than FAPbI₃.Finally,a DFB laser device was successfully fabricated using tri-cation perovskite.The threshold is only 75.9μJ/cm²...