Preparation And Optical Properties Of Novel Perovskite Nanomaterials

Since the perovskites were used as the photosensitive materials in solar cells,perovskite materials have become research focuses.In recent years,perovskite halide nanocrystals have been caught extensive concerns due to high quantum yield,narrow emission lines and enhanced optical properties.The organic-inorganic hybrid perovskite crystals have unique application in laser,field effect transistor due to their excellent photoelectronic properties.However,considering the toxicity of lead perovskite,environmentally friendly bimetallic perovskites have become the new trend of research.herein,three kinds of new perovskite nanocrystals(NCs)have been prepared by colloid chemical synthesis method,CsPbBr3-x(SCN)x?(C8H17NH3)2(C4H9NH3)n-1PbnBr3n+1 and(C4H9NH3)2AgBiBr6.Synthetic parameters and optical properties of these NCs have been furthur investigated.The research contents are as following:(1)Pure CsPbBr3 and a series of SCN-doped CsPbBr3-x(SCN)x monodisperse colloidal nanocrystals were prepared under nitrogen atmosphere,with CsCO3,PbBr2,Pb(SCN)2 as raw material.The morphology,crystal structure and optical properties analysis show that:compared with pure perovskite,the SCN-doped perovskites maintain the original cube morphology,but the size decreases slightly.Lattice configuration remains unchanged,while the crystallinity increases.The absorption and fluorescence emission peak occur blue shift,from 514 nm to 496 nm.The theoretical investigation revealed that the dominant effect of SCN-doping in CsPbBr3 would up-shift the CB position rather than the modification of VB position as other halide doping,and then result in the band gap broadening.(2)A series of different layersperovskite(C8H17NH3)2(C4H9NH3)n-1PbnBr3n+1(n=1,2,3)NCs were synthesized in both vacuum condition and in air,with brominated butylamine,lead bromide,brominated octylamine as raw material.The effects of reaction time,reaction condition,ratio of raw material and acidity on the products were explored to optimize the experimental conditions.The study found that,perovskites with different layers were synthesized by changing the molar ratio of precursors in the vacuum line condition,with reaction time of 1 h.The band gap decreases along with the increase of n,and the fluorescence also has a red shift.The band gaps of the products synthesized in the acidity condition showed slight changes.However,the lattice configuration changes obviously,which may be caused by crystal defect.(3)A series of(C4H9NH3)2AgBiBr6 NCs perovskite NCs were prepared in nitrogen atmosphere,by adjusting the amount of HBr,with AgBr?BiBr3,brominated butyl amine as raw materials.The product morphology,crystal structure were analyzed.We obtained uniform perovskite quantum dots with high crystallinity.The lattice configuration of products under different acidity condition keeps unchanged.A certain amount of acidity will lead to lattice defect for the(C4H9NH3)2AgBiBr6 NCs.The investigation of the optical properties reveals that:with the increase of HBr,their fluorescence peak occur an obviously red shift,increased from 404 nm to 470 nm.The PL peaks of the products,which are dissolved in different polarity solvent,are also biased.With the increasing of the polarity,the emission peak turns to red.