Study On Optimization And Electroluminescent Devices Based On Perovskite Bromide Films

Over the past few years,the appearance of an organic-inorganic metal halide perovskite material makes people's attention focused on photovoltaics,light emitting devices,lasers,and sensors.Compared with traditional semiconductor materials,this new type of semiconductor material has many advantages such as wide source of raw materials,simple solution processing,simple synthesis,high carrier mobility,adjustable band gap,and spectrum control.Since 2014,Tan from Cambridge University realized methylamine lead bromine(MAPbBr3)as the main luminescent material emits light at room temperature for the first time.The performance of its perovskite light-emitting diodes has greatly improved in short period of several years.However,perovskite materials still have many problems in the field of electroluminescent devices,such as improving the crystal morphology of perovskite films,reducing leakage current,and improving their stability.Based on the research of organic electroluminescence devices,this paper prepared high-quality perovskite films in the use of perovskite light-emitting diodes which improve the brightness and efficiency.The main work includes the following three aspects:1.Based on the one-step spin-coating process for the preparation of perovskite films,different volumes of phenylethylamine solution were added to the precursor of MAPb Br3 perovskite.We analyzed the relationship between the morphology of the MAPbBr3 film formed by the phenethylamine solution and crystal characteristics,combined with the corresponding device performance test results,to explore the performance of phenethylamine solution on MAPb Br3 perovskite film and optimize the prepare process.Finally we obtained the maximum brightness 29268 cd/m2 and the highest efficiency of 9.81 cd/A of perovskite light-emitting diodes.2.We studied the effects of different additives on the morphology and device performance of perovskite films,such as aniline bromide,benzylamine bromide,and phenylethylamine bromide.These researches revealed the law of performance,which is adding phenylalkylamine bromide with different chain lengths to the final perovskite light-emitting diode.It was found that if the two-dimensional material was not added,the MAPbBr3 would form larger film particles,lower coverage,poor fluorescence intensity and fluorescence lifetime.When excessive amount of aniline bromide,benzylamine bromide or phenylethylamine bromide was introduced into MAPbBr3,the film coverage reaches 100%.With the continuous increase of the content of two-dimensional material,aniline bromide influence the perovskite film greatest.The film coverage rate sharply decreased and particles became larger.Phenethylamine bromide had little change,and the film coverage was still high.It can be concluded that the longer chain length,the greater impact on MAPbBr3.The longer chain length,the transmission performance of the light emitting diode is more poor,resulting in poor performance of the light emitting diode.But the stability of the light emitting diode is better.Conversely,the shorter chain length,the light-emitting diode transmission become better.But when the content of MAPbBr3 slightly reduced,the coverage of the film is drastically reduced,resulting in a larger leakage current of the perovskite light-emitting diode,which deteriorates the performance and stability of the perovskite light-emitting diode.3.The preparation of perovskite-free and perovskite(CsPbBr3)thin films in the air,and by adjusting the proportion of CsBr,PbBr2 to regulate the crystal structure.the study found that when the addition of CsBr is not excessive,the crystallinity of the CsPbBr3 thin film is poor,and the presence of dendritic crystal growth,At the same time,it also results in poor film coverage.As the proportion of CsBr addition gradually increases,the crystallinity of the CsPbBr3 thin film becomes better and better,the particles decrease obviously,the coverage of the thin film increases remarkably,the growth is inhibited by appropriate amount of CsBr,and the conversion from the initial dendrite into Cubic crystals.In addition,when CsBr is excessive in the thin film,different crystal structures are formed,resulting in a strong fluorescence intensity of the thin film,and the performance of the device is greatly improved.Finally,we obtained a high-performance perovskite light-emitting diodes with an efficiency of 4.6 cd/A and brightness of 43686 cd/m2.