Research On The Dynamic Process Of Carriers In All-inorganic CsPbX₃ Perovskite

In recent years,metal halide perovskite materials,as an emerging material,have potential applications in solar cells,catalysis,lasers,photodiodes and other fields due to their excellent photoelectric properties.Compared with organic-inorganic hybrid perovskite materials,all-inorganic perovskite materials have more excellent thermal and chemical stability,and become a potential technology to improve the stability of perovskite batteries.The disadvantage is that the photovoltaic active phase of the high-efficiency all-inorganic perovskite material CsPbI3 is prone to phase transition at room temperature.Therefore,the quantum confinement effect is used to solve the problem of the easy phase transition of inorganic perovskite at room temperature and expand its application in solar cells,light-emitting diodes,and lasers and other fields.In this paper,using inorganic perovskite materials and the following questions are mainly explored:1.The quantum dot perovskite battery with quantum confinement effect has attracted the attention of researchers because it can produce multiple excitons after being excited,but the stable nanostructure needs the assistance of long-chain organic ligands with poor conductivity,it makes carriers more difficult for external circuits to recombine.Studies have shown that the combination of graphene conductors with excellent characteristics into perovskite quantum dots can effectively improve the transport performance of carriers,thereby improving the performance of solar cell devices.However,the transport mechanism of carriers in graphene/perovskite composites is still unclear.In order to explore the carrier transport process,we prepared CsPbI3 perovskite quantum dots and composited them with graphene.Using transient spectroscopy and other characterization methods,we explored the kinetic process between the two materials.By comparing the transient absorption and transient fluorescence spectra of graphene composites with different mass concentrations,it is inferred that the introduction of graphene can induce the transfer of photogenerated holes in CsPbI3 perovskite quantum dots to graphene,effectively promoting the separation of photogenerated charges.This work uses transient absorption and transient fluorescence spectroscopy to directly observe the hole transfer between composite materials,which provides new ideas for the study of carrier dynamics.2.Quasi-two-dimensional perovskite solar cells are favored by researchers because of their superior water and oxygen stability compared to traditional perovskite solar cells.The introduction of long-chain organic molecules into the polycrystalline film prepared by the one-step solution method can not only form quasi-two-dimensional structure,but also passivate defects,but because the quasi-two-dimensional phase composition is not single,the factors affecting the formation of the internal phase composition uncertain.In order to control the phase composition more precisely,we successfully controlled the composition of the three-dimensional phase in the RP quasi-two-dimensional CsPbI3 perovskite polycrystalline film with different n values by changing the annealing temperature and time.Using X-ray polycrystalline diffraction,Absorption emission spectroscopy and transient absorption spectroscopy analyze the phase composition and distribution in the film.It is found that the three-dimensional phase components in the film increase with the increase of annealing temperature and time,and are mainly distributed on the surface of the film.This work comprehensively studied the effects of annealing temperature and duration on the composition of quasi-two-dimensional perovskite phases with different n values,provided a technical basis for the preparation of quasi-two-dimensional thin films.3.CsPbBr3 perovskite has larger exciton binding energy and superior optical properties,it has potential application value in the field of light-emitting diodes and lasers.The introduction of long-chain organic molecules into the CsPbBr3 perovskite film can effectively reduce the surface roughness of the film and reduce light loss,thereby obtaining a lower amplified spontaneous emission（ASE）threshold.However,the influence of organic molecules with different chain lengths on the film is not the same,the difference between the chain lengths of organic molecules is unclear.In order to explore the effects of organic molecules with different chain lengths on the performance of ASE,we introduced benzylamine,phenethylamine,and amphetamine into the precursor solution to prepare a CsPbBr3 polycrystalline film,used atomic force microscopy,absorption emission spectra and transient absorption spectra to characterizes of different chain lengths.It is found that as the chain length increases,a two-dimensional structure appears in the film,which increases the surface roughness of the film and reduces the carrier lifetime.Finally we get the film with a low threshold and a high optical gain coefficient is obtained.This work explored the influence factors of organic molecules with different chain lengths on the performance of ASE,and provided a new idea for the application of perovskite.