The Relationship Between Liminescence And Nanosturcture Of Halide Perovskite And Its Application In Light Emitting Diodes

Organometal halide perovskites(OHP)are promising materials for low-cost,high-efficiency light emitting diodes(LEDs).However,films with large three-dimensional(3D)OHP crystals exhibit slow radiative recombination.Incorporation of an organic phase has been shown to be effective in restricting crystal sizes and forming two-dimensional(2D)OHP.In films with a distribution of 2D OHP nanosheets and small 3D nanocrystals,an energy funnel can be realized that concentrates the excitations in highly efficient radiative recombination centers.However,this energy funnel is likely to contain inefficient pathways as the phase separation between the OHP and the organic phase,and the dielectric confinement are currently poorly controlled.Based on these,the main work contained in this paper as follows:1.Layered and quantum well structure are formed in CsPbBr3 perovskite system by cooperating phenylethylammonium bromide(PEABr)molecule.The poor morphology of CsPbBn perovskite film is effectively controlled and a compact uniform film with high photoluminescence efficiency is obtained by this method.However,resulting from the strong π-π stacking between PEABr molecules,the PEABr crystal are easily formed which will lead to phase separation between organic and inorganic phases,reduced energy transfer and inefficient dielectric confinement in this organic-inorganic hybrid system.2.The PEABr crystal and phase separation between organic and inorganic phases are inhibited effectively through the addition of judiciously selected molecular additives to solution processed OHP films.The interaction between additive and PEABr molecule increase the steric hindrance between PEABr molecules,leading to suppressed PEABr crystals and enhanced dielectric confinement in perovskite film.As results,the photoluminescence quantum yield(PLQY)of perovskite film is enhanced in three orders and up to～70%.3.We use these improved material properties(pin-hole free,ultra smooth morphology and high PLQY)to report OHP LEDs with current efficiency of 49.1 cd/A and external quantum efficiency of 15.5%.What’s more,the joule heat during LED operation is reduced and the stability of LED device is lengthen by lower the nonradiative recombination pathway in perovskite film.