Preparation And Optical Properties Of Bismuth Based Perovskite Nanomaterials

Metal halide perovskite materials have attracted researchers’attentions in various fields because of their simple manufacturing process,adjustable bandgap,excellent charge transferance and high photoelectric conversion efficiency.However,most of the researches contained Pb element about novel perovskite nanomaterials.Cosidering the toxicity and instability of Pb,the preparation of lead-free perovskite materials with low toxicity and strong fluorescence is of great significance.In this paper,inorganic Cs₃Bi₂X₉ quantum dots,Cs₃Bi₂Br₉ nanoflowers and organic-inorganic doped（PEA）₂BiBr₅（PEA:phenylethylamine）nanosheets were prepared by using cooperative solvent ligand-assisted re-precipitation（Co-LARP）reaction.Their optical properties and basic information were also studied.The inorganic Cs₃Bi₂Br₉ quantum dots were prepared with the present of oleic acid and octylamine bromide as surface ligands and octane as antisolvent.Cs₃Bi₂Br₉nanoparticles were also synthesized without ligands for comparation about physical structure,optical properties and stability.It was found that the Cs₃Bi₂Br₉ quantum dots coated with oleic acid and octylamine bromide own good thermal stability and highly luminescent properties,with narrow FWHM,considerable PLQYs and obvious quantum confinement effect.In addition,effective anion exchange,which is a reversible reaction,could be performed when chloride and iodide ions are introduced.This method allowed the fluorescence of the Cs₃Bi₂X₉ quantum dots could be adjusted in the range of blue and green light.Furthermore,two-dimensional Cs₃Bi₂Br₉ nanosheets were obtained under the conditions of replacing the ligands with oleic acid and octylamine,which could accumulate and grow to form uniform nanoflowers with sizes of several hundreds nanometers.These nanoflowers possess high crystallinity and regular morphology with uniform shape and sizes.Their absolute PLQY was measured by the integrating sphere with a value of 8.4%,exhibiting excellent optical properties.And the optical properties exhibited clear quantum confinement effect,indicating these nanoflowers appear characteristics of ultrathin nanosheets in spite of the large overall sizes.In addition to pure inorganic metal halide perovskite materials,organic-inorganic layered perovskite nanosheets（（PEA）₂BiBr₅）were also prepared in this paper.In contrast to their inorganic counterparts,these nanosheets exhibit excellent crystallinity and apparent preferential orientation growth properties.This phenomenon could be attributed to the effect of the large volume of the benzene in the phenylethylamine,which effectively controls the thickness and growth direction of the nanoplatelets.