Research On Quasi-two-dimensional Perovskite Films And Electroluminescent Devices

In recent years,organic-inorganic hybrid perovskites have achieved rapid development in the field of optoelectronics due to their adjustable band gap,low-temperature solution-processing and high carrier mobility.However,some matters with the traditional three-dimensional（3D）perovskite have always limited the development of light-emitting devices,such as surface and internal defects,poor device stability,and exciton dissociation.Deeping research on perovskite materials,it has been found that low-dimensional perovskite materials,it has been found that low-dimensional perovskite materials can improve the luminous efficiency and stability of perovskite light-emitting diodes（PeLEDs）.While 2D perovskites materials can increase exciton binding energy and show fewer defects,larger insulating organic groups hinder charge transport and limit the luminous efficiency in PeLEDs.A quasi-two-dimensional perovskite mixed with 2D and 3D perovskites has drawn attention.This kind of perovskite materials can take into account the advantages of both 2D and 3D structures,increasing exciton binding energy and enhancing carrier transport.However,quasi-two-dimensional perovskites are not a perfect material,defects still exist,and fluorescence efficiency is still low.Besides,some mechanisms in low-dimensional structures are not yet clear,such as the process of film crystallization,exciton characteristics.In this thesis,we study the effect of large organic cation and solvent engineering on the morphology and properties of quasi-two-dimensional perovskite of（R-NH3）2MAn₁PbnBr3n+i structure from two aspects.The research results are as follows:1)Changing the chain length of organic ion R-NH3 in quasi-2D perovskite with（R-NH3）2An-1MnX3n+1 structure,the effect of large organic cation on optoelectronic properties is investigated.It is found that the long chain would hinder the formation of layered（R-NH3）2PbBr4 2D perovskite which is benefit to the increase of fluorescence lifetime,exciton binding energy and luminescence efficiency.2)Our results reveal the earlier addition of anti-solvent contributes to the luminescence of the film.However,the fast crystallization rate makes it difficult to control the dropping time of antisolvent.It was proved that the combination of DMSO/DMF blend solvent is beneficial to control the dropping time.3)We applied optimized solvent conditions to fabrication of the quasi-2D perovskite films and devices with different organic ligands.XRD,absorption and luminescence spectra,fluorescence lifetime,PLQY and device performance were compared and analyzed.It was proved that the combination of DMSO/DMF blend solvent,antisolvent use and large organic cation selection could significantly improve the quality of quasi-2D perovskite films.