Studies On Synthesis,Structures And Properties Of Thiourea Modified Lead Iodides And Perovskites

Recently,potential applications of organic-inorganic hybrid metal halide materials and perovskites in solar cells,photocatalysis and photoluminescence have attracted great attention.Organic-inorganic hybrid metal halides have abundant topology structures varied from one-dimensional(ID)chains,two-dimensional(2D)layers,and three-dimensional(3D)perovskite networks.The dimension can be modified through two ways,the one was the ratio of metal ions and halide elements and the other was the type and structure of organic cation.To date,most studies focus on the structures of hybrid metal halide achieved by changing the organic cation or using their mixtra.Nevertheless manipulating the different dimensional crystal structures of halide perovskites with the same organic caion system or introducing other transition metal ions are rare in comparation with the cation change methods.In this work,we introduced thiourea(tu)/Cu(I)and thiourea(tu)/MA into the lead iodide system to study their unique structures and optical properties.The research ideas and the main contents of thesis are as follows1.In introduction,the development history of organic-inorganic hybrid perovskite solar cells is reviewed briefly.The structures of organic-inorganic hybrid metal halides,including lead-iodide frameworks,the influence of organic cations or introduced heterometals on topologies were summerized.Then the applications of metal halides in optical and electronic materials were introduced.Finally,the research ideas and the main contents of the thesis were showed last2.A novel 1-D lead iodide compound with a high-symmetric structure was reported,which was synthesized by introducing thiourea(tu)and Cu(I)ion into the lead iodide system.The new compound,(tu)2Cu2PbI4(1),is a rare and perfect self-assembling example of one-dimensional lead iodides that is packed with tetrahedral orientation.The 1-D PbI3 chains in compound 1 are corner-shared with tetrahedral Cu4I6S4 clusters forming a high-symmetry cubic space group Ia3d(No.230).The packing orientation of 1-D chains in 1 should be first found.Finally,the fluorescence and photocurrent response properties of compound 1 were explored.3.A series of new hybrid lead iodide perovskites with MA and tu(thiourear)were synthesized by solvothermal method.The compounds are 1-D ribbon-like perovskites formulated as MAn(Htu)n+1PbnI4n+1(n = 2,3,4;denoted as 2-4).The ribbon width is increases with the n from two corner fused PbI6 octahedra to four octahedra.Temperature and solvent induced 1-D to 3-D perovskite transfer were found and discussed.The samples were characterized by online time-related XRD patterns,IR,XPS,TG and CHNS microanalysis and the results confirmed the structure transfer between 1-D to 3-D perovskite.Usually,only small organic cations such as methylammonium can incorporate into the 3-D perovskite structure.This study found that the thiourea molecule was incorporated into the 3-D perovskite structure.But where is the tu molecules located in the crystal?It should be further studied.