Chemical Synthesis Of Perovskite Semiconductor Nanocrystals And Research On Excitation State Dynamics

Because of the high absorption of light,quantum efficiency and carrier mobility,the perovskite semiconductor has a broad application in the field of photoelectric devices.As the size of materials gets into nanoscale,even approach to Bohr diameter of exciton,quantum confinement effect will cause the narrowing of fluorescence spectrum and the enhancement of quantum efficiency,which further expand its application prospect.But the exist of biexciton auger effect and dark state will make negative effects on the lasing and LED applications of perovskite semiconductor,respectively.Therefore,we research the influence of component and confinement effect at biexciton and dark state by adjust the organic cation,halide ion and morphology of perovskite nanocrystals.So,we can give some guidance on the design of perovskite optical devices.First,we synthesis all-inorganic,formamidinium and methylammonium perovskite quantum dots and all-inorganic perovskite nanorods by ligand-assisted hot-injection synthesis and ligand-assisted re-precipitation method respectively.By the comparative study of the first three samples,we can discover the influence of organic cation in exciton dynamics.Similarly,by the comparative study of the all-inorganic perovskite quantum dots and nanorods,we can discover the influence of confinement effect in exciton dynamics.Otherwise,we get all-inorganic perovskite quantum dots with different halide ions by ion-exchange method,which is used for researching the influence of halide ions in exciton dynamics.The research of exciton dynamics is focused on biexciton effect and dark states,which make negative effects on the optical applications of perovskite semiconductor.Researching the former,we find that when we make the iodide ions exchange,the biexciton lifetime will be longer and the biexciton effect will be weaker.But small amount doping will sharpen the potential well and strengthen biexciton effect.Confinement effect is in direct proportion to biexciton effect.Stronger the confinement effect,stronger the biexciton effect.Researching the latter,we find that when we make the iodine ions exchange,the proportion of slow process and the influence of magnetic field are increasing.And the energy splitting of bright excited level and dark excited level is smaller.The exist of organic group will weaken the exchange interaction by reason of charge screening effect.Which will reduce the energy splitting likewise.Based on above study,we know how to reduce the biexciton effect and dark states by controlling the component and morphology of perovskite nanocrystals.But in practical application,we need to consider from many aspects and can not make a hasty decision.For example,iodide ions exchange can weaken the biexciton effect,but it will cause band gap narrowing and spectrum redshift.So we need a deeper research to make overall arrangements on them.Nevertheless,the application of perovskite semiconductor still have room for development.Researching on its exciton dynamics will make some contribution to the future applications.