Study On The Construction And Properties Of Metal Halide Perovskites Induced By Organic Amines

Metal halide perovskites（MHPs）are an important class of crystalline materials with exceptional structural and property tunability.The cations in the three-dimensional MHPs replaced by larger sized organic cations,which can build various low-dimensional MHPs（LDMHPs）at the molecular level,such as 2D,1D,and 0D metal halide crystal materials.In this thesis,through the in-situ reaction of organic amines with formic acid/acetic acid,the cyclic cations generated by the reaction were used as templates to induce new metal halide perovskite materials with different dimensions,and during the synthesis process,three examples of compounds that use protonated organic amines as templates were discovered,and their properties such as fluorescence,phase transition,and nonlinear optics were studied.The details are as follows:1.Using solvothermal method,2-methyl-4,5-dihydro-1H-imidazol-3-ium（MDHID）,2,5-dimethyl-4,5-dihydro-1H-imidazol-3-ium（DDHID）,3,3’-（ethane-1,2-diyl）-bis（3,4,5,6-tetrahydropyrimidin-1-ium）（EDTM）and3,4,5,6-tetrahydropyrimidin-1-ium（THPM）as organic cations were generated by cyclization of ethylenediamine,1,2-diaminopropane,N,N’-（ethane-1,2-diyl）bis-（propane-1,3-diamine）and 1,3-diaminopropane with formic acid/acetic acid,respectively.five new metal halide perovskite materials[MDHID]_2n[Pb I₃]_2n（1）,[DDHID]_n[Pb I₃]_n（2）[EDTM]_1/n[Pb I₃]_n（3）,[EDTM]_n[Pb₄Cl₁₀]_n（4）and[THPM]_n[Mn（COOH）₃]_n（5）were synthesized.The structure analysis showed that the inorganic parts of compounds 1,2and 3 were all 1D chain structure with cations located around the one-dimensional chain.And 4 was 2D layered structure,with cations located in the interlayer.5 is a three-dimensional cage-like structure in which cations are located.Interestingly,4 and3 use the same organic amines and both cyclize with formic acid to form（EDTM）,but the use of halogens results in the presence of two compounds with different dimensions.The fluorescence test showed that the emission of 4 at 292 nm was centered on 407 nm and 543 nm.The fluorescence intensity at the emission wavelength of 407 nm gradually decreased with the increase of temperature,while for the emission at 543 nm,the fluorescence intensity first increased and then decreased with the increase of temperature.The variable temperature structure test shows that 5was crystallized in the Pnma space group at 293 K;it is crystallized in the Im-3m space group at high temperature of 455 K.And further verified by DSC test,5 has obvious reversible structural phase transition.2.Three new perovskite materials[H₄EDPM]_n[Pb Br₆]_n[H₂O]_2n（6）,[H₃APDM]_2n[Pb₃Cl₁₂]_n（7）and[HNEt₃]_2n[Ag₅I₇]_n（8）were synthesized using Protonated N,N’-（ethane-1,2-diyl）bis-（propane-1,3-diamine）,3,3-diaminodipropyla-mine and triethylamine（NEt₃）as template in solvothermal conditions.The structure analysis shows that the inorganic part of 6 is[Pb Br₆]^4-type single core cluster zero-dimensional structure,and the inorganic part of 7 is two-dimensional layered structure,and the protonated organic amine cation（H₃APDM）is in disorder state.8has a one-dimensional chain structure,and the inorganic chain is partially disordered.Protonated organic cations（HNEt₃）are distributed around the one-dimensional chain.The fluorescence test showed that 6 and 7 exhibited the strongest emission peaks centered at 558 nm and 563 nm when the optimal excitation wavelength was 354 nm and 305 nm,respectively,and the emission intensity decreased with the increase of temperature.Since 8 is crystallized in the chiral space group P3₂,the second-order frequency doubling effect and piezoelectric tests were performed on it.The frequency doubling effect test shows that the SHG intensity is 1.16 times that of KDP.When the frequency is 110 Hz,the value of piezoelectric coefficient d₃₃ obtained along the[001]direction at room temperature is 5.2 p C/N,which is 1.14 times of KDP（4.54 p C/N）.