Research On High Performance Perovskite Optoelectronic Devices

Metal halide perovskite,a new type of semiconductor material,has the advantages of low cost solution processing,high color purity,high quantum yield and good thermal stability.Light-emitting diodes based on perovskite materials?PeLEDs?show great application prospects in the fields of lighting and display in the future.However,the shortcomings of poor quality of neat perovskite film,unbalanced carrier injecting and transporting as well as low internal quantum efficiency are the main problems for the further development.Thus,enhancing the quality of perovskite film,improving the carrier injecting and transporting balance as well as increasing the internal quantum efficiency are the critical ways to improve the performance of the PeLEDs,which has also become the goal in the field of optoelectronic devices to obtain good performance.In this paper,we focus on optimizing the concentration of additives to obtain a continuous,smooth and fully covered perovskite film,improve balanced carrier injecting and transporting as well as increase the internal quantum efficiency,resulting in the high performance of the PeLEDs.The main content of this thesis is composed of the following parts:Chapter 1:first of all,the history and development of display technology are described.Next,the development of metal halide perovskite materials and its optoelectronic devices are introduced,including the history of perovskite materials,the process of preparing perovskite thin films and the physical basis of PeLEDs.Finally,the main content and purpose of this paper are briefly introduced.Chapter 2:as we know that the functional films are stacked to fabricate the PeLEDs.Therefore,the quality of perovskite film and optoelectronic behavior play an important role in the performance of the PeLED.Thus,this chapter is mainly to describe the instruments for characterizing properties of perovskite films and testing the photoelectric performance of the PeLEDs.Chapter 3:a full coverage all-inorganic cesium lead halide perovskite CsPbBr₃ film isachievedbyintroducingasmallorganicmoleculematerial,1,3,5-tri?m-pyrid-3-yl-phenyl?benzene?TmPyPB?,as a solution additive.The light-emitting diode?LED?using this CsPbBr₃:TmPyPB perovskite film as light emitting layer exhibit improved electroluminescent?EL?performance with the maximum brightness of 22309 cd/m²,highest current efficiency of 8.77 cd/A,and external quantum efficiency?EQE?of 2.27%,which are 8.6,10.2 and 10.3 times to that of neat CsPbBr₃ film based LED,respectively.The enhanced EL performances are ascribed to less current leakage due to full coverage,and improved electron transporting in the CsPbBr₃:TmPyPB perovskite film.Chapter 4:all-inorganic cesium halide perovskite materials are intensively investigated due to its excellent photoelectric characteristics,but poor film coverage,unbalanced charge carrier transporting and insufficient exciton harvesting are remain challenges to obtain high electroluminescent?EL?performance in perovskite light-emitting diodes?PeLEDs?.However,these problems can be overcome by introducing both a phosphorescent sensitizer?FIrpic?and an electron transporting material?TmPyPB?into all-inorganic cesium halide perovskite?CsPbBr₃?.And highly efficient green PeLEDs with full coverage CsPbBr₃:TmPyPB:FIrpic film as the emissive layer have been achieved,exhibiting the maximum luminance of 37784 cd/m²,the maximum current efficiency of 22.6 cd/A and the corresponding maximum external quantum efficiency?EQE?of 5.85%,where the EQE is 48-fold to that of neat CsPbBr₃PeLEDs.The enhanced EL performance is attributed to less non-radiative current leakage,better film surface passivation effect,balanced charge carrier injecting and transporting,as well as better exciton harvesting.It is believed that our work will provide an effective strategy to further improve EL performance of PeLEDs.