Fabrication And Photoelectric Properties Of Blue Perovskite Light-Emitting Diode Devices Based On Quasi-Two Dimensional Structure

At present,the development of blue Perovskite Light-emitting diode(PeLEDs)is still relatively slow,because the realization of blue emission requires a larger optical band gap,which is usually achieved by halogen engineering and dimension reduction engineering.But these two methods have their own limitations,resulting in the current situation of low efficiency and low stability of blue PeLEDs.Therefore,to solve the above problems,in this paper,the organic layer is partially modified in the film of perbromine system/bromo-chloride blend system based on quasi-two-dimensional structure.Under the action of metal ion passivation and regulation of the film phase distribution,the high efficiency of sky-blue and deep-blue PeLEDs are respectively realized.Specifically through the following aspects to carry out research and discussion:Part I:We use an organometallic ligand(PTCA)doping method to passivate halogen vacancy defects in two-dimensional perovskite films,introducing metal ions without introducing too much halide.Through the passive effect of K+and C=O in the introduced PTC A,the photoluminescence spectra of perovskite films under ultraviolet(UV)illumination,thermal stress and different bias voltages are stabilized successfully.Part 2:We achieve deep blue PeLEDs by adding guanidine salts without introducing too many insulating organic cations and chloride ions.Guanidine species can increase the formation energy of low-dimensional phase,especially when n=2,which is conducive to the formation of ideal low-dimensional phase distribution,thus significantly inhibits the cascade energy transfer between different species and allows the emission of deep blue.Finally,we prepared deep blue PeLEDs provide external quantum efficiency(EQE)in excess of 3.4%(～457 nm)and have a stable EL spectrum.Part 3:we explore the influence of fluoride additives on the phase distribution of the film,and summarizes that among the fluoride additives with different structures,the additives with non-coincident structure of positive and negative charge centers,such as(Pentafluorophenyl)diphenylphosphine(D-PFPO)and Bis(perfluorophenyl)(phenyl)phosphine(B-PFPO),will lead to the increase of low-dimensional phase(unwanted phase)content in the film,resulting in inefficient energy transmission.For the additive with coincident positive and negative charge centers,such as Trifluorophenyl phosphine(TPFPO),it will significantly reduce the content of low-dimensional phase in the annealed film,so that the phase distribution is more uniform and the energy transmission becomes efficient.