Study On Photoelectric Optimization Of Quasi-two-dimensional Perovskite Light-emitting Diodes With Organic-inorganic Hybridization

Compared with conventional three-dimensional(3D)perovskites,quasi-two-dimensional(2D)perovskite thin films have become a hot research topic due to their unique structural characteristics and optoelectronic properties.However,how to regulate the crystallization process of thin films to achieve the generation of different perovskite phase structures and phase components,and how the phase structure of perovskite affects the brightness and luminescence efficiency of thin films and devices are still important issues for perovskite light-emitting devices.The optimization study of polycation mixing and stoichiometric ratio is expected to further clarify this scientific issue.Based on this,quasi-two-dimensional chalcogenide light-emitting devices with the structure of indium tin oxide(ITO)/poly(3,4-ethylenedioxythiophene)polystyrene sulfonate(PEDOT:PSS)/quasi 2D perovskite/2,2',2"-(1,3,5-Benzinetriyl)-tris(1-phenyl-1-Hbenzimidazole)(TPBi)/LiF/Ag.The quasi-2D perovskite films and PeLED devices with different phase structures and components were obtained by optimizing the stoichiometric ratios of perovskite precursors using C6H5CH2CH2NH3Br(MABr),CH(NH2)2Br(FABr)and C6H5CH2CH2NH3Br(PEABr)as cationic dopants and revealing the generation of quasi-2D perovskite phase structures and their influence on the lightemitting devices.The main research works are as follows:Firstly,the perovskite luminescent films with different stoichiometric ratios were obtained by tuning the stoichiometric ratios of the perovskite precursor solutions,and the differences in the photovoltaic properties of three perovskite films with PEABr:MABr:PbBr2 molar ratios of 0:1:1,2:8:8 and 2:3:3,respectively,were compared.The mechanism of the effect of different stoichiometric ratios on the optical properties of the perovskite films was analyzed.The surface passivation of the perovskite thin films was achieved through the optimization of the antisolvent treatment process of the perovskite thin films.The experimental results show that the surface of perovskite films is smoother and flatter with the best PL and EL emission effect when the antisolvent drip time is 54s and the spin-coating rate is 3000r.m.p.The resulting PeLED devices have a maximum emission brightness of 11224 cd·m-2 and a maximum EQE of 2.11%.It is shown that at a PEABr:MABr:PbBr2 molar ratio of 2:8:8,the perovskite films with a distinct layered structure can effectively limit the spatial distribution of charges and enhance the radiation recombination efficiency of perovskite films by suppressing exciton dissociation.Secondly,quasi-2D perovskite films with FA/PEA binary cations were obtained by replacing MA by FA at the A-site ion,from which three perovskite films with PEABr:FABr:PbBr2 molar ratios of 0:1:1,2:8:8 and 2:3:3,respectively,were prepared.The photovoltaic performance of the different perovskite films and the electroluminescence of different PeLED devices were investigated,and it was shown that the optimal photovoltaic properties of the PeLED devices were obtained for a PEABr:FABr:PbBr2 molar ratio of 2:8:8.Meanwhile,FA/PEA binary cationic perovskite has better energy level matching compared with MA/PEA benchmark 2D perovskite,which improves the charge injection efficiency of the device and thus enhances the EL efficiency of FA/PEA-based PeLEDs.In addition,the addition of MAC1 to the perovskite precursor solution and doping of Cs+ in the hole injection layer PEDOT:PSS dispersion can effectively passivate the surface defects and improve the surface morphology of the perovskite film and improve carrier transport efficiency and suppress the leakage current generation of the device.Based on the synergistic enhancement effect of double halogen ions,the current efficiency of the PeLED device was increased from 5.4 cd·A-1 to 12.9 cd·A-1,and the efficient green light emission of the perovskite light-emitting device was achieved.Finally,the effects of different stoichiometric ratios on the structural and optical properties of the films were analyzed by modulating the PEAI,MAI and PbI2 stoichiometric ratios,and quasi-2D PeLEDs based on I were prepared in exploratory manner.The results show that the thermal quenching of excitons due to the Ibased 2D perovskite material at room temperature severely affects the radiation recombination efficiency,resulting in electroluminescence was not produced which quasi-2D PeLED devices were prepared.