Study On Sky-blue Layered And Green Perovskites Light Emitting Devices Based On Ethylammonium Bromide

The organometallic halide perovskite has been extensively studied in the field of luminescence because of its excellent properties such as solution processability,high luminescence quantum yield,large exciton binding energy,and band gap tunability.At present,the research of perovskite light-emitting devices is mainly concentrated on green light and red light devices,and blue light devices are an indispensable component of display devices,and research work is still relatively rare.Among the blue light-emitting devices,one uses Cl^-and Br^-/Cl-mixed anion high-bandgap perovskite materials as the light-emitting layer,and the device has low external quantum efficiency,and the other uses low-dimensional calcium-titanium.Mineral structures such as quantum dots and quantum flakes use quantum size effects to increase exciton binding energy and blue shift the luminescence spectrum.This thesis mainly studies the synthesis of methylamine and ethylamine mixed cationic perovskite materials to prepare luminescent materials,and prepares blue light-emitting devices by adjusting the molar ratio between methylamine?CH₃NH₃Br?and ethylamine?C₂H₅NH₃Br?.The external quantum efficiency of the blue light-emitting device is improved,and the luminous efficiency and stability of the device are improved.Further fine adjustment of the molar ratio between the mixed cations improves the external quantum efficiency and power efficiency of the green light-emitting device.At the same time,in order to further improve device efficiency and device lifetime,the passivator phenylmethylamine?PMA?was used to reduce the defect density of the device sample and inhibit the entry of moisture,and the external quantum efficiency of the light-emitting device with or without passivation agent?PMA?was investigated.,PL transient lifetime and the effect of photoluminescence quantum yield.This thesis mainly studies the sky blue layered perovskite light-emitting device and high-efficiency green light-emitting device based on ethyl bromide?EAPbBr₃?material,which mainly includes the following aspects:?1?Preparation of MABr,EABr and PbBr₂ molar ratio fixed at 1:1.5,wherein the MABr and EABr molar ratios are 1:1 and 1:1.3,respectively,compared to the CH₃NH₃PbBr₃ sample,1:1 perovskite sample The diffraction pattern is very similar,indicating that Pero is infinitely doped with EA cations,but the intensity of the diffraction peak of the 1:1 perovskite sample is reduced,and the half width is broadened,which reflects the decrease in crystallinity of the 1:1 Pero sample;The diffraction peak of the Pero sample of 1.3 moves in a higher direction relative to the diffraction peak of C₂H₅NH₃PbBr₃,which is related to different sizes of MA and EA cations.The 1:1 sample of the Pero sample has a reduced grain size,which may be due to the inhibition of crystal growth by the large group of brominated amines,and this is consistent with the XRD measurements.The grain size of the Pero sample of1:1.3 increases as the molar ratio of EABr increases,which is due to the coordination of MABr,which forms small micelles in the precursor solution.The samples were measured by atomic force microscopy.All samples showed a relatively smooth and continuous morphology.The root mean square roughness of the samples decreased from 9.5 nm to 7.7 nm with the addition of molar ethyl ammonium bromide?EABr?.A further increase in EABR content increased to 12.3 nm.The AFM measurements are consistent with the results of the scanning electron microscope measurements.Due to the effective passivation of ethyl ammonium bromide,the addition of equimolar ethylammonium bromide increases the luminescence intensity by a factor of five,which is beneficial to the external quantum efficiency?EQE?of the green perovskite light-emitting device.It is noteworthy that the blue layered perovskite light-emitting device has a maximum EQE of 2.6%at 100 cd/m2 and a power efficiency of 1 lm/w,which is a significant improvement over previously reported devices.?2?Preparation of methylamine and ethylamine mixed cationic perovskite materials,further study PbBr₂/?MABr+EABr?molar ratio of 1:1.2,MABr/EABr molar ratio of 1:0,5:1,2:1 and 1:2.MAPbBr3,5:1,2:1 and 1:2 sample?100?diffraction peaks gradually move toward small angles,reflecting the effective introduction of larger EA cations into the three-dimensional perovskite crystal lattice resulting in an increase in lattice constant,?100?The diffraction peak-to-peak value is reduced,and the 1:2 sample?100?diffraction peak is cleaved.The addition of high concentration of EABr causes the material to phase-separate to some extent.The luminescence wavelength of the sample can be adjusted by varying the cation molar ratio.The device structure prepared was ITO-PSS:PEDOT-Pero-TmPyPB-CsF-AL.The green light-emitting device prepared by this structure has a maximum external quantum efficiency of 6.9%,a power efficiency of 23 lm/W,and a chromaticity of?0.175,0.768?.?3?Further optimization based on the PbBr₂/?MABr+EABr?molar ratio of 1:1.2,MABr/EABr molar ratio 2:1 green light-emitting device,and the addition of passivating agent PMA to 2:1 green The properties of the luminescent sample device were analyzed for the effects of film surface morphology?SEM?,crystal structure?XRD?,photoluminescence?PL?and electroluminescence?EL?.The passivator PMA ratio was compared to 0.01%for 2:1 device efficiency and performance improvement,as well as for changes between current,voltage and brightness.It can be seen from the SEM that as the PMA content of the passivating agent increases,the grain size of the pero sample decreases.The pero of the passivating agent PMA was similar to the diffraction pattern XRD of the 2:1 pero sample.We compare the current,brightness,photoluminescence and other measurements of the original device with passivation agent PMA and no passivation agent.The addition of passivation agent PMA increases the luminescence quantum yield of the original device to 53.92%,and the current becomes smaller.The luminous efficiency is significantly improved by nearly1.5 times.This may be related to the reduction of the defect density of the device and the inhibition of moisture ingress,further limiting the charge transfer,thereby increasing the radiation recombination efficiency.The device structure prepared was ITO-PSS:PEDOT-Pero-PMA-TmPyPB-CsF-AL.The 2:1 device light-emitting device to which the passivating agent PMA is added is preferably about 42.5 cd A^-1.The maximum fluorescence quantum yield was 52.94%and the maximum external quantum efficiency was 11.36%.