Study On The Growth Of New Lead Halide Perovskite Crystals

The new lead halide-based perovskite material represented by CsPbX₃(X=Br,I,Cl)has a large light absorption coefficient,photoluminescence,high quantum efficiency,long optical carrier lifetime and long diffusion length,etc.The excellent photoelectric performance has successfully attracted the attention of researchers.And widely used in light-emitting diodes,lasers,photodetectors,solar cells,high-energy ray detection and other fields.At present,researchers'research on this material is mainly concentrated on thin films and quantum dots.Compared with thin films and quantum dots,bulk materials have a structure strictly arranged in accordance with crystallography,so they have higher stability and uniformity.Therefore,we have carried out a study on the growth of a new type of lead-halide-based perovskite crystals and characterized the optical properties of the obtained crystals.The main findings are as follows:1?CsI:Pb(0.01mol%,0.05mol%,0.1mol%,0.5mol%)crystals of different Pb²⁺concentrations were grown using the vertical Bridgman method.Before heat treatment,the crystals were sliced for spectroscopic testing.Subsequently,the influence of different atmospheres on the luminescence characteristics of crystals with different concentrations of CsI:Pb(0.01mol%,0.05mol%,0.1mol%,0.5mol%)was systematically studied,and try to precipitate CsPbI₃ perovskite quantum dots inside the crystal through different heat treatment processes Under vacuum and N₂ atmosphere at400?for 15h,the furnace was cooled and annealed.No new excitation emission peaks were found,and the peak intensity of the original spectrum was reduced.And the weaker peaks of the crystal in the range of 408nm?440nm all disappear.2?The CsPbBr₃ and CsPbBr_3-xCl_x(X=0.1,0.3,0.9,1.5)mixed crystals were grown by the vertical Bridgman method.It is found that the crystal color gradually changes from orange to yellow with the increase of Cl^-doping content.The photoluminescence peak appears blue-shifted,indicating that the band gap has been enlarged.By testing the spectra of the crystal and calculating the band gap,it is found that the Cl^-doping leads to an increase in the band gap,from 2.25 e V to 2.33 e V.When the halogen changes from Br to Cl,the energy level of the halide np⁶ orbital decreases,the valence band potential increases,and the optical band gap becomes larger.It is a feasible method to adjust the perovskite crystal to achieve a suitable optical band gap by halogen doping.3?The two-step method of swinging furnace and vertical Bridgman method is used to solve the problem of excessive vapor pressure of CuBiI₄ material in the process of polycrystalline material preparation and crystal growth.Through XRD verification,a CuBiI₄ crystal rod was initially grown,with a size of ?17*70mm.