Study On The Micronano Structure Control And Performance Of Perovskite Luminescent Devices Regulated By Aromatic Organic Cations

Perovskite light-emitting diodes(PeLEDs)have high color purity and luminance efficiency LEDs and have been considered as a promising candidate for next generation of lighting and display.In this thesis,a variety of large aromatic organic cation salts are used to prepare green and blue perovskite LEDs.The effect of various large organic cations on the crystal structure,film quality and density of defect states of perovskite films is investigated and the intrinsic relationship between crystal structure,film property and device performance of PeLEDs is established.The main studies are as follow:(1)Three trimethyl aromatic quaternary ammonium salts,benzyltrimethylammonium bromide(BTABr),benzyltrimethylammonium chloride(BTACl)and phenyltrimethylammonium bromide(PTABr)are used as additives for perovskite films and LEDs prepared by one-step spin-coatig process.The results reveal that the addition of quaternary ammonium salts improves the film coverage rate and reduces the defect density.The steric hindrance effect of aromatic quaternary ammonium cation inhibit the overgrowth of perovskite crystal,reduces the grain size and increases the probability of hole-electron recombination.The perovskite LED(PeLED)assisted with BTABr has the best performance with the maximum brightness and current efficiency of 12026 cd/m~2and 1.27 cd/A.(2)Long-chain quaternary ammonium hydrobromide salts with bigger large organic cations,including tetrabutylammonium bromide(TBABr),benzyltriethylammonium bromide(BTEABr)and benzyltributylammonium bromide(BTBABr),are selected as additives to prepare perovskite films and PeLED via one-step spin-coating.Results suggest that the larger organic cation can further reduce the grain size.Unlike trimethyl aromatic quaternary ammonium salts,TBA~+,BTEA~+and BTBA~+do not form low-dimensional perovskite because the number of carbon atoms in the alkane chain attached to the N atom is more than one.PeLEDs based on BTBABr achieve the best performance with a maximum brightness,CE and external quantum efficiency(EQE)of 23646 cd/m~2,3.39 cd/A and 0.82%.(3)Pure bromine quasi-2D dimensional perovskite nanocrystal films and PeLED devices with stable sky-blue light emission were prepared by using phenylethylammoniumhydrobromide(PEABr),trimethyl-substituted p-fluoro-trimethyl hydrobromide(F-PTABr)and tributyl-substituted BTBABr.When PEA~+is used as a skeleton and with the assistance of F-PTA~+,BTBA~+can be successfully filled into the interlayer of the lead halide octahedra of quasi-dimensional perovskite crystals.As a result,smaller grain size,wider band gap,narrower phase distribution and higher luminous color purity are achieved in perovskite films by using mixed large organic cations strategy.(4)Br/Cl mixed halogen perovskite films and electroluminescent devices were prepared by using DPGABr as an additive.Immovable DPGA~+formed abundant hydrogen bonds with halogen anions in perovskite crystals and inhibited the migration of halogen ions in perovskite.With the assistance of DPABr,the distribution of halogen ions become more uniform and the driving force of migration is reduced.The defects of perovskite film were passivated and the main channels of ion migration were blocked.The pure blue(474 nm,EQE=0.74%)and sky blue(484.3 nm,EQE=3.07%)PeLED with stable spectra were prepared successfully.