Morphology Control Of Inorganic Halide Perovskite Quantum Dots And The Applications In Optoelectronic Devices

In recent years,the halide perovskite（ABX₃）have received enormous attention due to their unique photovoltaic and optoelectronic performances.As the new generation semiconductor material,it has a unique structure.By regulating the metal ions in the A,B position and the halide ions in the X position,the properties of all aspects can be regulated.In addition to the 3D perovskite,low dimension halide perovskite has emerged a lot of attention due to its unique properties.The crystallographic dimensionality of the halide perovskite materials can be regulated by the periodic intercalation of long chin ions,adjusting the connection patterns of the PbX₆ octahedra.The dimensionality can be modulated among0-dimention（0D）,1-dimention（1D）,2-dimension（2D）and 3-dimension（3D）.Compared with the 3D halide perovskite,the 2D counterpart dis-plays abundant structural diversity and functionality.So far,various organic/inorganic cationic molecules,including ammonium,amidinium,imidazolium,large cation with benzene etc.,have been used as periodic spacers to inhibit the formation of 3D perovskite structure by replacing the A-site ions(e.g.Cs⁺,CH₃NH₃⁺,and HC（NH）²⁺).In addition,Gemini-type bi-functional molecules with two ionic terminal groups serving as linkers between layers,such as diamine,amino acid,etc.,have also been reported to obtain the layered 2D perovskite with extra functionalities.However,there have been limited investigations on organic anionic serving as the spacers to contruct layered 2D halide crystals.In this work,by introducing organic anions（e.g.pentanedioic acid（PDA）and hexanedioic acid（HDA）simultaneously）,the leaf-shaped（Cs₃Pb₂Br₅）₂（PDA-HDA）microplates with layered 2D structure have been synthesized.They also exhibit significant photoluminescence（PL）centered at 540 nm with a narrow emission peak.The synthesis of single crystals of Pb（PDA）and Pb（HDA）allows us to clarify the crystal structure of（Cs₃Pb₂Br₅）₂（PDA-HDA）perovskite and its structural evolution mechanism further.Varity of characterization are introduced to verify the 2D crystal structure nature and the formation mechanism of the microplates,including TEM,XRD,XPS,FT-IR etc.It is found that the formation of lead dicarboxylate complexes is a key step leading to 2D perovskite material with anionic spacers.Moreover,the cooperative introduction of dicarboxylic acid pairs with appropriate lengths is thermodynamically favored for the 2D perovskite crystallization.The work is the first demonstration of 2D halide perovskite with anionic spacers,which also opens up a new approach to the growth of organic-inorganic hybrid 2D perovskite crystals.