Study On The Controllable Synthesis And Stability Of Caesium Lead Halide Perovskite Nanocrystals

CsPbX3(X=Cl,Br,I)perovskite nanocrystals(NCs)have excellent optoelectronic properties,which are expected to play irreplaceable roles in solar cells,LED,lasers and photodetectors,i.e.So the synthesis of CsPbX3 NCs has attracted broad attention and has gotten a great many achievements.However,there are still many questions to be resolved in the synthesis of CsPbX3 NCs,for example,the synthesis of stable red CsPbX3 NCs,the synthesis of high-quality CsPbX3 nanorods(NRs),the decrease of the toxicity of lead in CsPbX3 NCs and the controllable synthesis of cesium lead halide NCs with different dimensionality,so there is still much work to be done to develop the application of perovskite NCs in photoelectric field.In this thesis,I mainly focus on the controllable synthesis and the improvement of stability of CsPbX3 NCs,the summary of my research work is as follows:(1)Synthesis of stable red CsPb(BrxI1-x)3 NC.s:Form a passivation layer on the surface of iodine-rich perovskite NCs through a selective acetone-etching method,so significantly enhances the stability of red CsPb(BrxI1-x)3 NCs.(2)Research the determinative factor that influences the kind of products in hot injection synthesis of CsPbX3 NCs:We synthesize CsPbBr3 and Cs4PbBr6 NCs through amine-free method,choosing cesium acetate,lead acetate and tetra-octyl ammonium bromide as independent sources of cesium,lead and bromine,to study the effects of various reactants on the final products.We find that the molarity ratio of Cs/Pb dominate the final products,while the amount of bromine has relatively little effect to the final products.Besides,we research the role of oleylamine in the reaction system.We find that,due to the fact that oleylamine can strongly coordinate to the Pb ions,introducing oleylamine into the amine-free reaction will decrease the effective Pb amount in the reaction system and increase the molar ratio of Cs/Pb,which will lead to the formation of Cs4PbBr6 NCs.(3)Synthesize CsPbBr3 nanorods(NRs)with aspect ratios around 2-10:The high quality NRs are formed at the water-oil interface by regulating the concentration of ligand.The ligand of tetraoctylammonium bromide(TOAB)plays an important part in the forming of NRs.The quaternary ammonium cation(C8H17)4N+ from TOAB can effectively combine with the OA to form an ion pair,which effectively reduces the concentration of the free OA.Thus,as-formed CsPbBr3 nanocubes can't be effectively protected by OA,leading to oriented attachment at the interface.Meanwhile,because of the uniformity of the cubic CsPbBr3 nanocubes,the assembled structure easily transfers into the NR morphology.(4)Synthesize Mn2+ doping CsPbCl3 NCs by an amine-free method.We avoid the use of PbCl2 for choosing CsAc,Pb(Ac)2·3H2O,Mn(Ac)2·4H20 and didodecyldimethylammonium chloride as precursors.We provide an easy method to synthesize CsPbxMn1-xCl3 NCs.Besides,we regulate the luminescence of CsPb,Mn1-xCl3 NCs through halide anion-exchange reaction.(5)Synthesize ultralong CsPbBr3 nanowires through a solvothermal method:We find that the volume ratio of oil acid and oleylamine plays an important part in deciding the morphology of products.When the volume ratio of oil acid and oleylamine is 1/1,the product is nanowire;when the amount of oil acid is larger than the amount of oleylamine,the product is nanoplate.Besides,increasing the temperature of solvothermal will make the nanowire thicker.