| Perovskite light-emitting diodes（PeLEDs）have the advantages of low cost,tunabled band gap,high photoluminescence quantum yield and high color purity.PeLEDs have potential application prospects especially in the fields of intelligent display and lighting.At present,in order to realize the commercial development of PeLEDs,the primary task is to improve the luminescence efficiency and operational stability.In PeLEDs,it is particularly important to form the synergistic effect in the interface between functional layers.For example,the interfaces,such as between perovskite light-emitting layer/charge transport layer and glass substrate/air,bear the light loss due to the difference of refractive index.Furthermore,the surface defects of the perovskite film will affect the radiative recombination of excitons and hinder the injection and transportation of the charges.In this thesis,some available strategies are proposed to reduce the light loss in the interfaces and the surface defects of perovskite films.Firstly,the high quality of perovskite films was preprated by the compositional engineering in perovskite precursor to control the morphology,crystal structure and optical properties of perovskite.The compositional engineering includes organic ammonium salt and halide mixture.Organic ammonium salt will induce the formation of twodimensional/three-dimensional（2D/3D）mixed phase perovskite,which can improve charge transfer process and the radiation rate of excitons.Subsequently,the effects of halide mixing on the crystallization kinetics and crystal structure of perovskite films were investigated,and the impact of halide mixture on the morphology and optical properties of perovskite films also were studied.Finally,the morphology of perovskite film,efficiency and long-term stability of the device were optimized by introducing organic ammonium salt and halide mixture.The results show that the external quantum efficiency（EQE）was 10.4%based on 2D/3D mixed phase perovskite device.The half-lifetime（T50）of these devices reached 171.4 h at an initial luminance of 500 cd m-2.Secondly,on the basis of the previous work,the optical loss of each functional layer interface is optimized.Optical structures were prepared and transferred onto hole transport layer and glass substrate to adjust the light scattering effect at the interface between perovskite and hole transport layer and the surface of glass substrate.A multilayer energy cascade structure was adopting at the front electrode/perovskite interface to synergistically extract the trapped light to reduce light loss from the waveguide and substrate modes.Compared with flat device,the EQE of patterned PeLED was increased to 21.2%,which is 2.1 times of that of flat devices.The effect of different period nanostructures and dipole positions on the outcoupling efficiency of the device was simulated by FDTD optical simulation.The mechanism of the improving PeLED performance is verified.In addition,due to the enhanced outcoupling efficiency,the Joule heat in the patterned PeLED was reduced,resulting in T50 reached 4806.7 h at an initial luminance of 100 cd m’2.Third,we have demonstrated a surface defect passivation strategy to improve the efficiency and stability of PeLEDs via the assistance of guanidinium iodide.The GAI modification can enable the secondary grain growth with the formation of surface-2D/bulk3D heterophased perovskites.The morphology and optical properties of the perovskite films were improved by the secondary growth technology,which reduced the density of defect states and suppressed the nonradiative recombination.The hydrogen bonding interactions of GA+ions with halide vacancies can passivate the surface defects of perovskite films.After GAI modification,the champion PeLED was achieved an EQE of 17.1%with a pure redemission at 692 nm.In addition,the devices exhibit good reproducibility with an average EQE of 14.1%,and the improved operational stability with a half-lifetime of 563 min at an initial luminance of 1000 cd m-2. |
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