| Since the 20 th century,semiconductor quantum dot displays have more unique advantages than organic light emitting diodes(OLEDs)and have been favored,including narrow half-peak widths,adjustable emission wavelengths,very high fluorescence quantum yield(PLQY),and good Light and thermal stability,etc.Therefore,quantum dot light emitting diodes(QLEDs)with a simplified device structure,short response time,low power consumption,high contrast,and wide viewing angle have been considered as next-generation displays.Traditionally synthesized Cs Pb Br3 quantum dots use oleylamine and oleic acid as ligands.However,the poor conductivity of these ligands will inevitably affect the efficiency of the diode,so it is important to find a new ligand to replace these ligands.However,the perovskite body material has poor film-forming properties,and usually has large holes,which is not conducive to the recombination of excitons.Therefore,the performance of Pe LED can be improved only by solving the problem of film morphology.In this project,a Cs Pb Br3 perovskite quantum dot solution was first prepared,and its performance was compared using two methods: high temperature synthesis and room temperature synthesis.After comparison,we decided to use a room temperature synthesis method with better optical properties.Then we used three different holetransport layers,PVK,poly-TPD,and PTAA,to fabricate QLED devices with various structures,and observed that the device structure under different hole-transport layers can achieve higher performance.Experiments have found that the minimum lighting voltage of poly-TPD and PTAA devices is only 3.5V,the maximum brightness of polyTPD devices reaches 1118.7cd/m2,and the maximum EQE = 0.99% of PTAA devices.For the perovskite body material,in order to overcome the imbalance of the device's current input and poor film morphology,we modified the hole-transport layer PEDOT: PSS.By mixing the PEDOT: PSS solution and the silver amino nanoparticle solution at a volume ratio of 4: 1,a PEDOT: PSS hole transport layer treated with the silver amino nanoparticle solution was obtained.V is reduced to 3.5V,and the maximum brightness is increased to 3445.5cd/m2,which is more than 50% more than the basic device,and the effect is remarkable.In order to make the perovskite film smoother and denser,a new small molecule 1,3-bis 9H-carbazole-9-ylbenzene(m CP)additive was carefully designed to adjust the film morphology of the Cs Pb Br3 light-emitting layer.As an important phosphorescent host material,m CP plays a key passivation role in reducing defects and traps,which can effectively reduce non-radiative recombination.Even more surprising is that a unique Lewis acid-base reaction may occur between Cs Pb Br3 and m CP.Solid-phase chemical reactions can enhance the connection and film-forming ability of perovskite grains,and significantly reduce pinholes and grain sizes.In this way,a high-efficiency Pe LED with a high-quality Cs Pb Br3: m CP lightemitting layer was successfully realized.Benefiting from the introduction of m CP,a uniform and pinhole-free Cs Pb Br3 light-emitting layer was obtained,and its roughness was reduced from 8.28 nm to 1.62 nm.Optimized Cs Pb Br3: The maximum brightness value of the m CP device is 21008 cd/m2,and the corresponding maximum EQE = 1.21%.Finally,we have prepared a white LED device with a simple structure by evaporation.The device has a maximum brightness of 485.1cd/m2 and a maximum EQE=0.1%. |
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